阅读说明：本技术 用于使防腐剂溶液灭菌的系统、方法和装置 (Systems, methods, and devices for sterilizing antiseptic solutions ) 是由 萨蒂什·德高拉 克里斯托弗·马修·麦克金尼 肯尼斯·布鲁斯·瑟蒙德 于 2016-06-30 设计创作，主要内容包括：一种用于使防腐剂溶液灭菌的方法包括：提供多个含有防腐剂溶液的容器,该防腐剂溶液具有初始纯度；选择约85℃至约135℃的灭菌温度和约1分钟至约19小时的灭菌时间；将多个容器中的防腐剂溶液加热至所选择的灭菌温度；使防腐剂溶液保持所选择的灭菌时间；和当灭菌时间结束时,终止防腐剂溶液的加热。在终止加热之后,多个容器中的防腐剂溶液具有灭菌后纯度。选择灭菌温度和灭菌时间,从而使得在终止加热后,防腐剂溶液是无菌的,并具有至少约92％的灭菌后纯度,并且从初始纯度到灭菌后纯度的纯度百分点变化为至多约5％。(A method for sterilizing a preservative solution comprising: providing a plurality of containers containing a preservative solution, the preservative solution having an initial purity; selecting a sterilization temperature of about 85 ℃ to about 135 ℃ and a sterilization time of about 1 minute to about 19 hours; heating the preservative solution in the plurality of containers to a selected sterilization temperature; maintaining the preservative solution for the selected sterilization time; and terminating the heating of the preservative solution when the sterilization time is over. After termination of heating, the preservative solution in the plurality of containers has a post-sterilization purity. The sterilization temperature and sterilization time are selected such that, after termination of heating, the antiseptic solution is sterile and has a post-sterilization purity of at least about 92%, and the percentage point of purity from the initial purity to the post-sterilization purity varies by at most about 5%.)

1. A method for sterilizing a preservative solution, the method comprising:

providing a plurality of containers containing a preservative solution having:

0.1% to 2.5% w/v chlorhexidine gluconate; and

initial purity;

selecting a sterilization temperature of 85 ℃ to 135 ℃ and a sterilization time of 1 minute to 19 hours;

heating the preservative solutions in the plurality of containers to a selected sterilization temperature;

maintaining the preservative solutions in the plurality of containers at a sterilization temperature for a selected sterilization time; and

terminating heating of the preservative solution in the plurality of containers when the selected sterilization time is over;

wherein the preservative solution in the plurality of containers has a post-sterilization purity after terminating the heating,

wherein the sterilization temperature and the sterilization time are selected such that, after terminating the heating, the antiseptic solution in the plurality of containers is sterile and the solution in the plurality of containers has a post-sterilization purity of at least 98% and a percentage point change in purity from an initial purity to a post-sterilization purity of at most 2%, and

wherein the selected sterilization time and the selected sterilization temperature satisfy the following relationship:

a)90℃≤y<125℃，

x is more than or equal to 1 and less than or equal to 552, y is more than or equal to-6.14. ln x +123.2, and

x is more than or equal to 9 and less than or equal to 260, and y is more than or equal to-10.6. ln x + 148.3; or

b)125℃≤y≤135℃，

x is not less than 1, and

for x is more than or equal to 3.7 and less than or equal to 9, y is more than or equal to minus 10.6. ln x +148.3,

where y is the sterilization temperature and x is the sterilization time, expressed in minutes.

2. The method of claim 1, wherein:

the preservative solution comprises an alcoholic solvent selected from the group consisting of ethanol, isopropanol, and n-propanol.

3. The method of claim 1, wherein the preservative solution comprises 40% to 90% v/v isopropanol.

4. The method of claim 1, wherein the preservative solution comprises about 70% v/v isopropanol and about 2.0% w/v chlorhexidine gluconate, wherein the term "about" means ± 5% of the value provided.

5. The method of claim 1, wherein the sterilization time is 6 minutes to 1 hour.

6. The method of claim 1, wherein the sterilization temperature is about 95 ℃ and the sterilization time is from 1.5 hours to 6.5 hours, wherein the term "about" means ± 5% of the value provided.

7. The method of claim 1, wherein the sterilization temperature is about 110 ℃ and the sterilization time is from 6 minutes to 90 minutes, wherein the term "about" means ± 5% of the value provided.

8. The method of claim 1, wherein the sterilization temperature is about 120 ℃ and the sterilization time is from 2 minutes to 35 minutes, wherein the term "about" means ± 5% of the value provided.

9. The method of claim 1, further comprising:

providing a water spray sterilizer, the water spray sterilizer generating a spray water stream,

wherein heating the preservative solution to and maintaining the selected sterilization temperature comprises contacting the plurality of containers with a stream of spray water for the period of sterilization time.

10. The method of claim 9, further comprising providing a chiller that produces cooling water, the method further comprising cooling the water of the water spray sterilizer with the cooling water from the chiller.

11. The method of claim 10, further comprising drying the plurality of containers after cooling the sterile solution.

12. The method of claim 9, further comprising providing one or more steam generating boilers, the method further comprising heating water of the water shower sterilizer with steam from the boilers.

13. The method of claim 9, further comprising measuring a change in conductivity of the water spray sterilizer and correlating the measured change in conductivity with an amount of preservative solution present in the water.

14. The method of claim 9, further comprising placing the plurality of containers in a cassette, placing the cassette in a rack, and transferring the rack into a chamber of a water spray sterilizer.

15. The method of claim 14, wherein placing the plurality of containers in a box comprises vertically arranging the plurality of containers within a box.

16. The method of claim 15, wherein the plurality of containers comprises 330 to 2000 containers.

17. The method of claim 15, wherein each of the plurality of containers holds 0.67mL to 3mL of the preservative solution, and the plurality of containers comprises 1800 to 2200 containers.

18. The method of claim 15, wherein each of the plurality of containers holds 10.5mL to 13mL of the preservative solution, and the plurality of containers comprises 300 to 350 containers.

19. A method for sterilizing a preservative solution, the method comprising:

providing a plurality of containers containing a preservative solution having an initial purity and 0.1% to 2.5% w/v chlorhexidine gluconate;

selecting a sterilization temperature of 85 ℃ to 135 ℃ and a sterilization time of 1 minute to 19 hours;

heating the antiseptic solution in the plurality of containers to a selected sterilization temperature and maintaining the antiseptic solution in the plurality of containers at the sterilization temperature for a selected sterilization time by contacting the plurality of containers with a spray stream of water produced by a water spray sterilizer for the sterilization time period;

terminating heating of the preservative solution in the plurality of containers when the selected sterilization time is over; and

the cooling water generated by the refrigerator is used for cooling the water of the water spray type sterilizer,

wherein the preservative solution in the plurality of containers has a post-sterilization purity after terminating the heating,

wherein the sterilization temperature and the sterilization time are selected such that, after terminating the heating, the antiseptic solution in the plurality of containers is sterile and has a post-sterilization purity of at least 98% and a percentage point change in purity of at most 2% from an initial purity to a post-sterilization purity,

providing a water shower sterilizer which generates a shower water flow, and

wherein the selected sterilization time and the selected sterilization temperature satisfy the following relationship:

a)90℃≤y<125℃，

x is more than or equal to 1 and less than or equal to 552, y is more than or equal to-6.14. ln x +123.2, and

x is more than or equal to 9 and less than or equal to 260, and y is more than or equal to-10.6. ln x + 148.3; or

b)125℃≤y≤135℃，

x is not less than 1, and

for x is more than or equal to 3.7 and less than or equal to 9, y is more than or equal to minus 10.6. ln x +148.3,

where y is the sterilization temperature and x is the sterilization time, expressed in minutes.

20. A method for sterilizing a preservative solution, the method comprising:

providing a plurality of containers containing a preservative solution having an initial purity and 0.1% to 2.5% w/v chlorhexidine gluconate;

selecting a sterilization temperature of 85 ℃ to 135 ℃ and a sterilization time of 1 minute to 19 hours;

heating the antiseptic solution in the plurality of containers to a selected sterilization temperature and maintaining the antiseptic solution in the plurality of containers at the sterilization temperature for a selected sterilization time by contacting the plurality of containers with a spray stream of water produced by a water spray sterilizer for the sterilization time period;

heating water of the water spray sterilizer with steam generated by one or more boilers; and

terminating the heating of the preservative solution in the plurality of containers when the selected sterilization time is over,

wherein the preservative solution in the plurality of containers has a post-sterilization purity after terminating the heating,

wherein the sterilization temperature and the sterilization time are selected such that, after terminating the heating, the antiseptic solution in the plurality of containers is sterile and has a post-sterilization purity of at least 98% and a percentage point change in purity of at most 2% from an initial purity to a post-sterilization purity,

providing a water shower sterilizer which generates a shower water flow, and

wherein the selected sterilization time and the selected sterilization temperature satisfy the following relationship:

a)90℃≤y<125℃，

x is more than or equal to 1 and less than or equal to 552, y is more than or equal to-6.14. ln x +123.2, and

x is more than or equal to 9 and less than or equal to 260, and y is more than or equal to-10.6. ln x + 148.3; or

b)125℃≤y≤135℃，

x is not less than 1, and

for x is more than or equal to 3.7 and less than or equal to 9, y is more than or equal to minus 10.6. ln x +148.3,

where y is the sterilization temperature and x is the sterilization time, expressed in minutes.

21. A method for sterilizing a preservative solution, the method comprising:

providing a plurality of containers containing a preservative solution having an initial purity and 0.1% to 2.5% w/v chlorhexidine gluconate;

selecting a sterilization temperature of 85 ℃ to 135 ℃ and a sterilization time of 1 minute to 19 hours;

heating the antiseptic solution in the plurality of containers to a selected sterilization temperature and maintaining the antiseptic solution in the plurality of containers at the sterilization temperature for a selected sterilization time by contacting the plurality of containers with a spray stream of water produced by a water spray sterilizer for the sterilization time period;

measuring a change in conductivity of the water spray sterilizer and correlating the measured change in conductivity with an amount of preservative solution present in the water; and

terminating the heating of the preservative solution in the plurality of containers when the selected sterilization time is over,

wherein the preservative solution in the plurality of containers has a post-sterilization purity after terminating the heating,

wherein the sterilization temperature and the sterilization time are selected such that, after terminating the heating, the antiseptic solution in the plurality of containers is sterile and has a post-sterilization purity of at least 98% and a percentage point change in purity of at most 2% from an initial purity to a post-sterilization purity,

providing a water shower sterilizer which generates a shower water flow, and

wherein the selected sterilization time and the selected sterilization temperature satisfy the following relationship:

a)90℃≤y<125℃，

x is more than or equal to 1 and less than or equal to 552, y is more than or equal to-6.14. ln x +123.2, and

x is more than or equal to 9 and less than or equal to 260, and y is more than or equal to-10.6. ln x + 148.3; or

b)125℃≤y≤135℃，

x is not less than 1, and

for x is more than or equal to 3.7 and less than or equal to 9, y is more than or equal to minus 10.6. ln x +148.3,

where y is the sterilization temperature and x is the sterilization time, expressed in minutes.

Technical Field

Aspects of the present invention relate to the field of sterilization, and in particular to sterilization of topical antiseptic solutions.

Background

In the united states, the requirements for sterilization of topical antiseptic solutions are currently not specified. Thus, preservative solutions currently sold in the united states are generally not subjected to sterilization processes. However, in other jurisdictions, such as the European Union (EU) countries, some degree of sterilization is required. A known preservative solution manufactured by Carefusion Corp. containing 2% w/v chlorhexidine gluconate (chlorexidine gluconate) in a 70% v/v aqueous isopropanol solution is sterilized using known sterilization methods when used in the European Union countries.

Known sterilization methods include heat treating glass ampoules containing chlorhexidine gluconate solutions in a convection oven at 76-80 ℃ for 24-31 hours. It is presently believed that relatively low temperatures and relatively long processing times are necessary to adequately sterilize the solution without excessive degradation of the antimicrobial molecules, thereby avoiding a reduction in the concentration and purity of chlorhexidine gluconate contained therein as a preservative. Degrading the antimicrobial agent molecules to produce undesirable impurities and reducing the total concentration of the active drug moiety. Regulations in the united states and european union countries limit the amount of impurities that may be present in preservative solutions. Furthermore, convection ovens that utilize air for heating are inefficient processes because it takes a relatively long time to heat the solution from room temperature (also referred to herein as a "ramp up" time) and eventually cool the solution back to room temperature (also referred to herein as a "cool down" time). For example, the ramp time for the solution to reach sterilization temperature may be 2-6 hours, while the cool down time may be 1-2 hours. Thus, the time that the chlorhexidine gluconate solution is exposed to the sterilization temperature (i.e., the time at 76-80 ℃) in known processes may be 22 to 24 hours, while the total processing time (i.e., including ramping, sterilization, and cooling times) may be about 25 to 32 hours.

It is believed that high temperature sterilization is not suitable due to the expected degradation. See, e.g., Kelly M.Pyrek, "Sterility of inflammatory Products: FDAInvestages, Deliberates on positional Recommendations," Infection Control Today (July 2013): 24-26; and Block, Seymour S.Disinfection, Sterilization, and Preservation Philadelphia Lippincott Williams & Wilkens, 322-323.2001.

Accordingly, there is an unmet need in the art for a method of sterilizing a preservative solution that has a shorter, more efficient processing time and provides a sterile solution while maintaining sufficient preservative solution purity to meet regulatory requirements.

Summary of The Invention

Aspects of the present invention overcome the above-identified problems, as well as others, by providing systems, methods, and devices for effectively sterilizing an antimicrobial agent solution while maintaining antimicrobial efficacy as a preservative and purity of the active pharmaceutical ingredient that meets regulatory requirements.

In one exemplary aspect, a method for sterilizing a preservative solution includes providing a plurality of containers containing the preservative solution, the preservative solution having an initial purity; selecting a sterilization temperature of about 85 ℃ to about 135 ℃ and a sterilization time of about 1 minute to about 19 hours; heating the preservative solution in the plurality of containers to a selected sterilization temperature; maintaining the preservative solution in the plurality of containers at the selected sterilization temperature for the selected sterilization time; and terminating the heating of the preservative solution in the plurality of containers when the selected sterilization time is over. After termination of heating, the preservative solution in the plurality of containers has a post-sterilization purity. The sterilization temperature and sterilization time are selected such that, after termination of heating, the preservative solution in the plurality of containers is sterile and has a post-sterilization purity of at least about 92%, and the percentage purity change from the initial purity to the post-sterilization purity is at most about 5%.

In another aspect, the sterilization temperature and sterilization time may be selected such that the selected sterilization time and the selected sterilization temperature satisfy the following relationship:

a)85℃≤y<125℃，

x is more than or equal to 1 and less than or equal to 552, y is more than or equal to-6.14. ln x +123.2, and

x is not less than 21.5 and not more than 1123, and y is not less than-10.38. ln x + 156.9; or

b)125℃≤y≤135℃,

x is not less than 1 and

for x is more than or equal to 9.1 and less than or equal to 21.5, y is more than or equal to minus 10.38. ln x +156.9,

where y is the sterilization temperature and x is the sterilization time in minutes.

In another exemplary aspect, the sterilization temperature and sterilization time are selected such that, after termination of heating, the antiseptic solution in the plurality of containers has a post-sterilization purity of at least about 94%, and the percentage point of purity from the initial purity to the post-sterilization purity varies by at most about 4%.

In another exemplary aspect, the preservative solution in the plurality of containers comprises an aqueous isopropanol solution at about 70% v/v and chlorhexidine gluconate at about 2.0% w/v.

In another exemplary aspect, the sterilization temperature is about 95 ℃ and the sterilization time is about 90 minutes to about 6.5 hours. In another aspect, the sterilization temperature is about 110 ℃ and the sterilization time is about 6 minutes to about 90 minutes. In another aspect, the sterilization temperature is about 120 ℃ and the sterilization time is about 2 minutes to about 35 minutes.

In another exemplary aspect, the selected sterilization temperature and the selected sterilization time are selected such that, after termination of heating, the antiseptic solution in the plurality of containers has a post-sterilization purity of at least about 96%, and the percentage point of purity from the initial purity to the post-sterilization purity varies by at most about 3%.

In another exemplary aspect, the selected sterilization temperature and the selected sterilization time are selected such that, after termination of heating, the antiseptic solution in the plurality of containers has a post-sterilization purity of at least about 98%, and the percentage point of purity from the initial purity to the post-sterilization purity varies by at most about 2%.

Additional advantages and novel features of various aspects of the invention will be set forth in part in the description which follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention.

Brief description of the drawings

FIG. 1 is a schematic flow diagram of an example sterilization system according to certain aspects of the present disclosure; and

fig. 2 is a graph of sterilization temperature and sterilization time data according to certain aspects of the present disclosure.

Detailed Description

Aspects of the present invention overcome the above-identified problems, as well as others, by providing systems, methods, and apparatuses for sterilizing preservative solutions while maintaining antimicrobial efficacy while complying with regulatory requirements.

Various aspects of the preservative applicator may be described with reference to one or more exemplary embodiments. As used herein, the term "exemplary" means "serving as an example, instance, or illustration," and should not be construed as necessarily preferred or advantageous over other embodiments of the sterilization methods disclosed herein.

As used herein, the term "about" preferably means ± 5%, and more preferably ± 1% of the value provided.

Aspects of the invention include methods of sterilizing a preservative solution contained in a container. The method may include heating the preservative solution contained in the container or ampoule to a temperature and maintaining the temperature for an amount of time sufficient to sterilize the solution while maintaining a purity of the preservative solution sufficient to comply with regulatory requirements. Antimicrobial efficacy is directly related to the purity of the preservative solution. Generally, when the purity of the preservative molecule is too low, the solution is not effective as an antimicrobial solution. In addition, higher impurity levels in the preservative solution can have deleterious effects on the health of the patient.

The container is preferably a self-contained structure formed of a material suitable for containing a preservative solution. In one aspect, the container may be made of a frangible material such that the container ruptures when sufficient force is applied. For example, the material may comprise plastic or glass. The terms "container" and "ampoule" are used interchangeably herein. The container walls may have a thickness sufficient to withstand sterilization processes, shipping, and storage. When the container is frangible, the material and thickness may also be sufficient to allow the container to rupture upon application of localized pressure. The thickness range may vary depending on the size of the container. Exemplary thicknesses for glass or plastic containers include about 0.15mm to about 0.45 mm. In another example aspect, the container may comprise a non-frangible material capable of withstanding the sterilization process, such as a metal, e.g., a bag comprising or consisting of a polymer and/or foil material, steel, aluminum, and the like. For example, the container may be a retort-like foil pouch having a composite of polymer and foil. An example thickness of the bag may be about 0.002 inches to 0.010 inches.

While particular attention is directed to preservative solutions herein, the container may alternatively contain a drug, chemical composition, cleaning agent, cosmetic or the like. For example, the container may be filled with a preservative composition (e.g., a composition comprising one or more preservative molecules), preferably an antimicrobial liquid or gel composition. For example, the preservative solution may contain inactive ingredients that have functions including moisturizing, skin smoothing, visualization, solubility, stability, viscosity, wetting, and the like.

The preservative solution may comprise an alcoholic solvent. For example, the alcohol solvent may be selected from the group consisting of ethanol, isopropanol, and n-propanol. The amount of solvent may be from about 40% v/v to about 90% v/v, more preferably from about 50% v/v to about 80% v/v, still more preferably from about 65% v/v to about 80% v/v. The remaining volume of the solution may be water or another solvent. For example, the solution may contain from about 10% v/v to about 60% v/v, more preferably from about 20% to about 50% v/v, still more preferably from about 20% to about 35% v/v water.

The container may contain a sufficient amount, concentration and purity of preservative solution to be applied to and have an antimicrobial effect on the desired surface. In one aspect, the desired surface is the skin of the patient. It should be understood that the amount of preservative solution may vary. In one aspect, the amount of preservative solution can be 0.01-100mL of preservative. More preferably, the amount of preservative solution required may be about 0.5-60mL, and still more preferably may be about 0.5-30 mL. Examples include 0.67, 1, 1.5, 3, 10.5 and 26mL of preservative. In cases where a larger volume of solution is desired, such as 26mL, multiple smaller containers (e.g., two 13mL containers) may be employed in a single applicator.

Suitable preservative molecules include bis (dihydropyridinyl) decane derivatives (e.g. octenidine (octenidine) salts) and/or biguanides (e.g. chlorhexidine salts). As used herein, the term "derivative" refers to a chemical that a) is structurally related to and derived from a first chemical; b) a compound formed from a similar first compound or a compound imaginable from another first compound if one atom of the first compound is replaced by another atom or group of atoms; c) a compound derived or obtained from the parent compound and containing an essential element of the parent compound; or d) a compound that can be produced in one or more steps from a first compound having a similar structure. Examples of biguanide/biguanide derivatives other than chlorhexidine/chlorhexidine salts include alexidine (alexidine), alexidine salts, polycaproamide, polyhexamide salts, polyaminopropyl biguanide salts, and other alkyl biguanides. Preferred preservatives include octenidine salts such as octenidine dihydrochloride (a bis (dihydropyridyl) decane derivative and cationic surfactants); and chlorhexidine salts, such as chlorhexidine gluconate (cationic biguanides). The concentration of preservative may vary depending on the particular preservative species used or the antimicrobial effect desired. For example, when octenidine or an octenidine salt is used, the concentration may be from about 0.0001% w/v to about 2.0% w/v, more preferably from about 0.01% w/v to about 0.5% w/v, still more preferably from about 0.1% w/v to about 0.4% w/v. When chlorhexidine or a chlorhexidine salt is used, the concentration may be from about 0.1% w/v to about 2.5% w/v, more preferably from about 0.5% w/v to about 2.25% w/v, still more preferably from about 1.2% w/v to about 2.0% w/v.

In one aspect, when chlorhexidine or a chlorhexidine salt is used, the purity of the solution may be at least about 92% pure, more preferably at least about 94% pure, still more preferably at least about 96% pure, and still more preferably at least about 98% pure when applied to the skin (e.g., after the sterilization process described herein). As used herein, purity means the percentage concentration of preservative molecules in solution relative to the total concentration of the concentration of preservative molecules plus the concentration of substances derived from or associated with the preservative molecules. For example, a 95% pure preservative solution means that if there are 100 molecules that are preservative molecules or molecules derived from or associated with preservative molecules, then 95 of the molecules are preservative molecules and 5 of these molecules are molecules derived from or associated with preservative molecules. These molecules derived from or associated with the preservative molecule have reduced or no antimicrobial activity. Thus, a lower purity solution will have lower antimicrobial efficacy because less of the target preservative molecule is delivered to the skin of the patient. In addition, a less pure solution will not meet regulatory requirements. By measuring the concentration of preservative molecules in the solution as compared to the concentration of preservative molecules and molecules derived from or related to the preservative molecules, one can determine the purity of the solution and whether the purity is sufficient to meet regulatory requirements.

In a preferred aspect, the preservative solution provided in the container comprises about 70v/v of an alcoholic solvent in water and about 2.0% w/v of a preservative molecule. In a preferred aspect, the solvent may be isopropanol and the preservative molecule may be chlorhexidine gluconate.

It has been found that when the preservative solution in the container reaches a particular temperature and is held at that temperature for a particular amount of time, the solution is sufficiently sterilized while maintaining sufficient antimicrobial efficacy as a preservative and while meeting regulatory requirements. In one aspect of the invention, the preservative solution may be brought to a temperature of from about 85 ℃ to about 135 ℃, more preferably from about 90 ℃ to about 125 ℃, still more preferably from about 95 ℃ to about 120 ℃ (also referred to herein as a "sterilization temperature").

As used herein, the term "sterilization time" means the length of time that a solution is at a sterilization temperature. That is, "sterilization time" does not include the time it takes for the solution to reach the sterilization temperature (i.e., does not include "ramp up" time), and does not include the time it takes for the solution to return to the temperature at which the solution was at prior to heating (i.e., does not include "cool down" time). The time it takes for the temperature of the solution to reach the sterilization temperature is referred to herein as the "ramp up" time, and the time to return to the starting temperature is referred to herein as the "cool down" time. As used herein, the term "sterilization temperature" means the temperature or temperature range that a solution reaches and is maintained during a sterilization time, regardless of the starting temperature of the solution. For illustrative purposes only, for a solution with an initial temperature of 21 ℃, a sterilization time of 90 minutes and a sterilization temperature of 95 ℃ means that the time period from the moment the solution reaches 95 ℃ to the moment the solution drops below 95 ℃ during the start of the cooling process is 90 minutes. Therefore, the time taken for the solution to rise from 21 ℃ to 95 ℃ (i.e., the ramp-up time) and the time taken for the solution to return to 21 ℃ (i.e., the cooling time) are not included in the sterilization time.

The predetermined sterilization times and sterilization temperatures provided herein generally assume that thermal exposure during ramping up and cooling does not affect sterilization of the pharmaceutical product, as on a small scale, these processes may be considered transient. However, on a commercial scale, the time taken to heat the product will affect the overall lethality of the sterilization process, such that the steady state sterilization time is reduced. When applying the effects of ramping up and cooling to the cycle, sterilization of a pharmaceutical product may be described by calculating F-values for each of the predetermined sterilization times and sterilization temperatures using the following equations (see "Laboratory Manual for Food cans and Processors", vol.1, AVI Publishing co., Westport, CT, 1968):

wherein:

t is the temperature of the sterilized product at a particular time T.

Δ T is the time interval between subsequent measurements of T.

Ts is target sterilization temperature

Z is a temperature coefficient, generally assumed to be equal to 10 ℃, but is calculable for the particular microorganism and is therefore a variable.

For illustrative purposes only, a sterilization temperature of 121 ℃ and a predetermined sterilization time of 6 minutes (i.e., ramping up and cooling does not affect sterilization of the pharmaceutical product) corresponds to a minimum F value (F) at 121 ℃ for sterilizing the pharmaceutical product₁₂₁) Was 6 minutes. This minimum required F value can be used to quantify the process in which ramping up and cooling does affect sterilization of the pharmaceutical product. In such a process, the effect of the ramp up and cooling on the minimum required F value can be calculated. If at F₁₂₁F was calculated as the sum of the heat input during the actual cycle, not reaching a temperature of 121 ℃, during the sterilization cycle defined as 6 minutes₁₂₁The period parameters can still be met.

In one aspect, the sterilization time may be no more than about 19 hours, more preferably no more than about 13 hours, more preferably no more than about 5 hours, more preferably no more than about 3 hours, more preferably no more than 2 hours, more preferably no more than 1 hour, more preferably no more than 40 minutes, more preferably no more than about 25 minutes, more preferably no more than 6 minutes, and more preferably no more than 1 minute.

It has been found that the combination of sterilization temperature and sterilization time can be selected to provide a sterilized preservative solution having a purity sufficient to comply with regulatory requirements when used as a preservative. For example, for a sterilization temperature of about 85 ℃, the sterilization time may be at least about 9 hours to about 19 hours. For a sterilization temperature of about 95 ℃, the sterilization time may be at least about 1.5 hours up to about 6.5 hours. For a sterilization temperature of about 105 ℃, the sterilization time may be at least about 17 minutes to about 2.5 hours. For a sterilization temperature of about 110 ℃, the sterilization time may be at least about 6 minutes up to about 90 minutes. For a sterilization temperature of about 115 ℃, the sterilization time may be about 3 minutes to about 55 minutes. For a sterilization temperature of about 120 ℃, the sterilization time may be at least about 2 minutes and at most about 35 minutes. For a sterilization temperature of about 125 ℃, the sterilization time may be about 1 minute to about 22 minutes. For a sterilization temperature of about 130 ℃, the sterilization time may be at least about 1 minute up to 14 minutes. For a sterilization temperature of about 135 ℃, the sterilization time may be about 1 minute to about 9 minutes. In one aspect of the invention, the above exemplary sterilization temperatures and sterilization times may be applied to a preservative solution comprising about 70% v/v isopropanol and about 2.0% w/v chlorhexidine gluconate or other preservative solutions described above.

It has been found that heating the preservative solution contained in the container to the above-mentioned sterilization temperature and maintaining that temperature for the above-mentioned sterilization time is sufficient to sterilize the solution while maintaining a purity sufficient to comply with the legislation requirements. The amount of degradation of the preservative molecules can be quantified by measuring the initial purity of the preservative solution prior to the ramped temperature rise time (i.e., prior to the process of raising the solution to the sterilization temperature) and measuring the post-sterilization purity of the preservative solution after the cooling time (i.e., after the preservative solution is returned to the temperature at which the solution was prior to the process of raising the solution to the sterilization temperature). Thus, as used herein, "initial purity" is the purity before ramping up, and "post-sterilization purity" is the purity of the solution after cooling. In one aspect of the invention, the preservative solution (e.g., chlorhexidine gluconate) may have an initial purity of at least about 94%, preferably at least about 97%, and more preferably at least about 98%. The meaning of purity is provided above. The resulting sterilized solution was found to have a purity sufficient to provide the desired antimicrobial efficacy as a preservative and to meet regulatory requirements.

In one exemplary aspect, it has been found that chlorhexidine gluconate molecules degrade upon heat treatment into one or more of the following molecules: n- [ [6- [ [ [ (4-chlorophenyl) amidino ] amino ] hexyl ] amidino ] urea (N- [ [6- [ [ [ (4-chlorophenyl) carbamimidoyl ] carbamimidoyl ] -amino ] hexyl ] carbamimidoyl ] urea), N- (4-chlorophenyl) guanidine, N- (4-chlorophenyl) urea, 1- (6-aminohexyl) -5- (4-chlorophenyl) biguanide, N- (4-chlorophenyl) -N' - [ [6- [ [ [ (4-chlorophenyl) amidino ] amino ] hexyl ] amidino ] urea, 1- (4-chlorophenyl) -5- [6- [ [ (phenylamidino) amidino ] amino ] hexyl ] biguanide, 1- [6- (amidino amino) hexyl ] -5- (4-chlorophenyl) biguanide and 4-chloroaniline. Thus, in one exemplary aspect, the purity of the solution may be determined by comparing the amount of chlorhexidine to the amounts of all chlorhexidine gluconate-related substances listed above. It should be noted, however, that the above list is not exhaustive. One of ordinary skill in the art will be able to determine which molecules are degradants of the preservative molecule after the sterilization process.

As described above, the purity of the preservative solution after heating is terminated and when the solution has been returned to the temperature at which the solution was prior to the process of raising the solution to the sterilization temperature (e.g., ambient temperature) is referred to herein as post-sterilization purity. As noted above, it is preferred to measure post-sterilization purity when the preservative solution has cooled, as degradation can occur during cooling. In one aspect of the invention, the post-sterilization purity can be maintained relatively close to the initial purity while still being sterile by selecting an appropriate combination of sterilization temperature and sterilization time. In particular, the combination of sterilization temperature and sterilization time is selected such that the percentage point of purity from the initial purity to the post-sterilization purity varies by at most about 5%, more preferably at most about 4%, more preferably at most about 3%, and most preferably at most about 2%. It is understood that a percentage change refers to the absolute percentage difference between the initial purity and the post-sterilization purity. For example, the change from 95% initial purity to 90% post-sterilization purity is a percentage point change of 5%.

In addition to maintaining sufficient purity, it has been found that an appropriate combination of sterilization temperature and sterilization time can be selected so that the solution is sterile. As used herein, sterile means "7-day sterile" as tested according to the procedures described in the following documents: pharmaceutical convention (USP) Chapter 55, "Biological Indicators-Resistance Tests," USP 36; the practice is formally carried out from 5/1 in 2013. Sterile also means completely free of microorganisms immediately after sterilization. In one aspect, Geobacillus stearothermophilus (Geobacillus stearothermophilus) can be used as the test microorganism. Thus, in one aspect, the sterile solution shows no growth of Geobacillus stearothermophilus by the "7 day sterility" test described above. In another aspect, the solution inoculated with Geobacillus stearothermophilus is completely free of viable Geobacillus stearothermophilus following the sterilization process.

In another aspect of the invention, the methods of the invention have been found to have at least about 10 at a particular combination of sterilization temperature and sterilization time^-6Sterility Assurance Level (SAL). SAL is a measure of the probability that microorganisms are present on an item after a sterilization procedure. 10^-6SAL of (a) means that the opportunity of 1/1,000,000 exists for viable microorganisms in the sterilized product. Thus, SAL measures the probability that a sterilization process will result in an unsterilized product. The calculation of the assay SAL is described in more detail in the examples below. For example, it has been found that methods of exposing a preservative solution to a temperature of 100 ℃ for about 50 minutes, 105 ℃ for about 17 minutes, or 110 ℃ for about 6 minutes will all have a temperature of at least 10^-6The chance of 1/1,000,000 being the presence of viable microorganisms in the sterilized solution.

As described above, after the sterilization time is over, the solution may be cooled. For example, it may take about 10 to about 40 minutes to cool the preservative solution after the sterilization time. A cooling device may be used to reduce this time. This additional time is associated with a particular sterilization temperature. For example, a higher sterilization temperature (e.g., 125 ℃) will take longer to return to room temperature after sterilization than a lower sterilization (e.g., 85 ℃). Thus, the total processing time including cooling may include an additional about 10 to about 20 minutes longer than the sterilization time.

It is within the scope of the present invention to use any machine capable of heating the antiseptic solution to a sterilization temperature and maintaining the solution at the sterilization temperature for a sterilization time while preferably limiting the ramp up time. An example device may include a water shower sterilizer (canning water sterilizer). When a water spray sterilizer is used, the ramp up time may be about 15 minutes and the cool down time may be about 25 minutes. Water spray sterilizers provide a constant flow of water that heats the solution to sterilization temperature, maintains the sterilization temperature throughout the sterilization time and eventually cools the solution.

As provided above, example combinations of sterilization time and sterilization temperature to provide a sterile solution having a purity sufficient to meet regulatory requirements are described below. For a sterilization temperature of about 85 ℃, the sterilization time may be about 9 hours to about 19 hours. For a sterilization temperature of about 95 ℃, the sterilization time may be at least about 1.5 hours up to about 6.5 hours. For a sterilization temperature of about 105 ℃, the sterilization time may be about 17 minutes to about 2.5 hours. For a sterilization temperature of about 110 ℃, the sterilization time may be at least about 6 minutes up to about 90 minutes. For a sterilization temperature of about 115 ℃, the sterilization time may be about 3 minutes to about 55 minutes. For a sterilization temperature of about 120 ℃, the sterilization time may be at least about 2 minutes and at most about 35 minutes. For a sterilization temperature of about 125 ℃, the sterilization time may be about 1 minute to about 22 minutes. For a sterilization temperature of about 130 ℃, the sterilization time may be at least about 1 minute up to 14 minutes. For a sterilization temperature of about 135 ℃, the sterilization time may be about 1 minute to about 9 minutes.

Fig. 1 shows a schematic flow diagram of an example sterilization system 100. In general, the sterilization system 100 may include one or more sterilizer units 102 (e.g., a water spray unit), a boiler 104, a chiller 106, a refrigerant pump reservoir 108, a deionized water pump reservoir 110, and a dryer 112. In operation, prior to the sterilization process, the plurality of containers are filled with the preservative solution. The container may be of various sizes to accommodate different volumes of solution. For example, the container can be sized to hold 0.67, 1, 1.5, 3, 10.5, and 13mL of preservative solution (in the case of a 13mL container, in certain aspects, two containers are placed in a single applicator to achieve a total of 26mL of solution in a single applicator). The container with the preservative solution is then loaded into the cartridge in a vertical upright manner. The cassette may be made of metal. The cartridge may be configured to be filled directly from a solution filling machine. The cassette may also be configured to be inserted directly into the assembly apparatus so that the containers are transferred with minimal manual handling. In one aspect, each capsule may weigh less than 20 pounds when fully loaded to minimize ergonomic risks associated with manual handling.

In a preferred aspect, all of the containers in the cassette have the same dimensions during a particular sterilization process because sterilization conditions vary based on the size and number of containers. The number of containers in each cassette will vary with the size of the container and the size of the cassette used. For larger containers, such as 13mL, about 300 to 350, more preferably about 330 containers, may be loaded in a single cassette. For smaller containers, such as 0.67mL, about 1800 to 2200, more preferably about 2000 containers, can be loaded in a single cassette. The plurality of cassettes may then be loaded into a rack containing a plurality of cassettes. For example, 1 to 144 cassettes may be placed in a single rack. Thus, for smaller containers, each rack may have up to 200,000 containers, and for larger containers, each rack may have up to about 50,000 containers. The following chart provides some exemplary embodiments of various containers in a sterilization system:

the system may be capable of sterilizing 1 or 2 racks at a time, although much larger systems are possible. Once the cassettes are loaded into the racks, each rack may be placed in the sterilization chamber of one sterilization unit 102. With multiple sterilization units 102, multiple sterilization processes may occur at the same time.

Once placed in the sterilization unit 102, the sterilization process may begin. Deionized water from the deionized water pump reservoir 110 may be pumped into the chambers of each sterilization unit 102 through input line 113. The process can be controlled and run using a computer control system with a specially programmed computer. The computer control may be specifically programmed so that the operating parameters will vary based on the type of container to be sterilized, among other parameters. The computer controller will instruct the system to provide the appropriate level of deionized water into the chamber for the particular product being sterilized. Deionized water is then circulated within the chamber.

While deionized water is circulating in the chamber, the computer control system may open a valve to allow steam from boiler 104 to enter sterilizer unit 102 through input line 114. The steam does not enter the chamber directly, but enters the heat exchanger. As with deionized water, the steam passes through a heat exchanger, which allows heat exchange between them without direct interaction between the steam and the deionized water. Steam condensate from the boiler 104 (now cooler due to heat exchange) may exit the heat exchanger and return to the boiler 104 via a return line 116. The cycle of heat exchange continues until the system measures that the temperature of the circulating deionized water is at the appropriate predetermined sterilization temperature. The system then precisely controls the input of steam to maintain the sterilization temperature, such as by actuating appropriate valves.

During this same time that heat exchange is occurring, the deionized water in the chamber is continuously circulated within the chamber so that the deionized water falls onto the containers in the cartridge (hence the term water shower). This process heats the preservative solution within the container.

As shown in fig. 1, more than 1 boiler (e.g., two) may be used to provide steam. Two boilers can be connected in series to provide redundancy if 1 boiler fails. Alternatively, 1 larger boiler may be applied.

Once the sterilization time has been completed, the computer control system will then initiate the cooling process. The cooling process is similar to the heating process except that chilled water (chilled water) is used and steam is used in the heating process. For example, the cooling water may be chilled via chiller 106. Chilled water may travel between the refrigerant pump reservoirs 108 via input/return line 111 so that the chilled water is ready for use. The chilled water may travel from the refrigerant pump reservoir 108 to the heat exchanger of the sterilization unit 102 via input line 118. As described above with respect to steam heat exchange, chilled water may exchange heat with deionized water, thereby cooling the deionized water and heating the cooling water. During this cooling heat exchange, deionized water continues to circulate within the chamber and fall onto the container. After heat exchange, the now warmed cooling water may travel back to the refrigerant pump reservoir 108 and enter the chiller 106 via line 120/111. The cooling cycle continues until the deionized water in the chamber has reached a desired temperature (e.g., room temperature).

After cooling of the deionized water is complete and sufficient time has passed to allow the preservative solution to cool, the deionized water can be drained so that when opened, the door is not opened to leak water. The racks of now sterilized containers may then travel down from the conveyor to the dryer 112. The dryer 112 is used to dry the outside of the container, which is wetted with deionized water during sterilization. Heated dehumidified air may be used to rapidly dry the container. In one exemplary aspect, the container containing the solution may be dried at an air temperature of less than 50 ℃ in about 1 hour. This allows the container to be ready for placement directly in the preservative applicator, which would not be possible if the container were wet. Furthermore, it has been found that the drying temperature and time period do not unduly degrade the preservative molecules within the container. The dryer may employ a large dehumidifier to pull water out of the air used to dry the container. Without a dehumidifier one would expect much higher temperatures and/or longer drying times. The drying cycle for various product loads can be optimized based on volume, bulk density (e.g., number of containers per box), and container spacing with solutions, among other factors.

The water shower sterilizer units can be placed below grade (below grade) so that they can be loaded without lifting the loading apparatus. Each sterilization unit may include a conductivity sensor to measure the change in water conductivity based on the amount of antimicrobial molecules present in the water used to sterilize the container containing the solution. By detecting the presence of antimicrobial molecules in the sterilized water, the operator can indirectly measure the amount of container breakage during each sterilization process. In other words, because the preservative solution is released into the circulating water when the container is broken, the concentration of the pharmaceutical product in the water allows the operator to estimate the number of containers broken during the process. The system may be configured such that if the conductivity sensor indicates that the water has an excess of antimicrobial (e.g., exceeds a predetermined threshold concentration), the sterilized water may be discharged directly into the hazardous waste.

The system may further include pallet handling equipment (pallet jacks) for use with the racks. The pallet handling equipment may be desirable because the racks are preferably made of stainless steel and weigh several hundred pounds. Since the cassette is also preferably made of stainless steel, the weight of the cassette plus the weight of the container means that each rack can weigh over 2000 pounds. A sparkproof electrically powered pallet handling apparatus is preferred because of the potential fire risk associated with the presence of isopropyl alcohol within the container.

The system may also include a bladder (not shown) between the deionization pump reservoir and the sterilizer. The bladder may be filled with deionized water up to a predetermined pressure. The pump may then be turned off and the bladder maintains pressure in the line, thereby preventing damage to the pump. When the chamber is filled with an open valve before the sterilization cycle is started, the pressure in the line immediately supplies water. The pump detects the pressure drop in the bladder container and continues to supply water as needed until the pressure in the bladder container returns to a predetermined point.

As described above, a program (i.e., a specially programmed computer) may be used to control the entire sterilization system. As described above, the program may allow the computer to communicate with the dryer to receive and transmit data, among other components of the system.

Examples

Samples of a preservative solution of 70% v/v isopropanol, 30% v/v water and 2.0% w/v chlorhexidine gluconate contained in glass ampoules were tested in each of the following examples. An inoculum of greater than 1,000,000 but less than 10,000,000 tested geobacillus stearothermophilus spores was inserted and sealed into the container. In the following examples, a 10mL sample of the preservative solution at room temperature was placed in a water or oil bath (water bath temperature 95 ℃ C.; oil bath temperature 100 ℃ C.) having a predetermined temperature (i.e., sterilization temperature). The ampoule containing the chlorhexidine gluconate solution and the test spores was placed in a heating medium. Samples with test spores were removed at specific times (i.e., sterilization times), allowed to cool to room temperature, and then tested and incubated for a period of seven days for bacterial growth. Samples of the preservative solution also stored at the set temperature were tested for the degradation of chlorhexidine gluconate. The 7-day bacterial growth test follows the procedure described in the following literature: pharmaceutical convention (USP) Chapter 55, "Biological Indicators-Resistance Tests," USP 36; the practice is formally carried out from 5/1 in 2013. Purity and sterility data for the chlorhexidine gluconate solutions collected, which were 98.67% pure prior to heat treatment, are shown in tables 1-6. The purity percentage values listed in the table are the absolute purity of chlorhexidine gluconate after heat treatment and cooling to ambient temperature. Percent delta purity values are percent changes from baseline purity. For example, in table 1, chlorhexidine gluconate has a purity of 98.05% at 78 ℃ and 4 hours, which varies by a percentage point of 0.62% from an initial purity of 98.67%.

TABLE 1-78 deg.C, initial purity 98.67%, water bath

TABLE 2-80 ℃ initial purity 98.67%, water bath

Tables 3 to 82℃Initial purity 98.67%, water bath

TABLE 4-85 deg.C, initial purity 98.67%, water bath

TABLE 5-90 deg.C, initial purity 98.67%, water bath

Tables 6 to 95℃Initial purity 98.67%, water bath

Additional experiments were performed in an oil bath to test the purity change at 105 ℃ and 115 ℃. The glass ampoules containing the preservative solution were subjected to the sterilization times and sterilization temperatures shown in tables 7 and 8 using an oil bath. The% change in purity of the preservative solution after the sterilization time was measured and compared to the initial% purity value. Measurements were taken after the solution returned to ambient temperature.

Tables 7 to 105℃Initial purity 98.7%, oil bath

Tables 8 to 115℃Initial purity 98.7%, oil bath

The above data were then used to prepare an Arrhenius equation (Arrhenius equation) using methods standard in the art. The use of the arrhenius equation is a well-known and accepted method of modeling the dependence of temperature on reaction rate. Using the arrhenius equation, the following predicted purity values were obtained:

TABLE 9 purity as predicted using Arrhenius equation

The effect of the measured respective sterilization temperatures and sterilization times on the characteristics of the preservatives is shown below. Table 10 summarizes the% change in purity of chlorhexidine gluconate after exposure to various sterilization temperatures and sterilization times. Percent purity change was obtained by comparing the purity of the solution before the ramped warm-up time (i.e., before the process of bringing the solution to the sterilization temperature) with the purity of the solution after the cool-down time (i.e., after the solution is returned to ambient temperature). "W" indicates that sterilization temperature and sterilization time will result in a change in purity of no more than 2%. "X", "Y" and "Z" indicate that sterilization temperature and sterilization time will result in no more than 3%, 4% and 5% purity change, respectively. Finally, "a" indicates that sterilization temperature and sterilization time will result in a purity change of greater than 5%.

TABLE 10 influence of heating and temperature on chemical stability

Note that: w-solution has a purity variation of not more than 2%

The solution has a purity variation of not more than 3%

The solution has a purity variation of not more than 4%

The solution has a purity variation of not more than 5%

A-solution has a purity variation of more than 5%

Table 11 summarizes the sterility of the preservative solutions measured containing greater than or equal to 1,000,000 but less than 10,000,000 test geobacillus stearothermophilus spores after exposure to the various sterilization temperatures and sterilization times.

TABLE 11 Effect of heating and temperature on sterility

Note that: the solution was sterile, as indicated by the absence of viable bacterial spores.

N-solution is not sterile, as evidenced by the growth of viable bacterial spores.

As shown in the above table, when the sterilization time and temperature are varied, there is a special window in which the treated preservative solution is sterile and has a purity variation of less than a certain percentage (e.g., 5%). It should be noted that since the above data is a threshold analysis, the results of other sterilization times can be extrapolated. Once the purity change is found to be at least 5% at a particular temperature and time, it can be speculated that a longer sterilization time at the same temperature will further degrade the solution. It is also speculated that all samples with the same initial purity value sterilized at the same temperature for a shorter time than found to have a purity change of less than 5% will also have a purity change of less than 5%. For example, the sample tested at 95 deg.C for 4 hours had a purity of 95.53%, while the sample tested at 95 deg.C for 6 hours had a purity of 94.74%. Thus, it can be extrapolated that all sterilization times greater than 6 hours at 95 ℃ will have a purity of less than 95.74%, while all sterilization times less than 4 hours at 95 ℃ will have a purity of at least 95.53%. Similarly, with respect to the seven day sterility test of USP, once a sample is found to have seven days sterility at a particular sterilization temperature and time, it is surmised that a longer sterilization time at the same temperature will also exhibit 7 days sterility (i.e., long term sterility). Thus, it can be speculated that all samples sterilized at the same temperature for longer than the time found to have seven days of sterility will have 7 days of sterility. It is also speculated that all samples sterilized at the same temperature in a shorter time period will also not have 7 days sterility compared to samples found not to have seven days sterility. For example, a sample tested at 95 ℃ for 1.25 hours is sterile after seven days, while a sample tested at 95 ℃ for 0.5 hours has bacterial growth within four days (i.e., no 7-day sterility). Thus, it can be extrapolated that all sterilization times of greater than 1.25 hours at 95 ℃ will be sterile after 7 days, while all sterilization times of less than 0.5 hours at 95 ℃ will have bacterial growth within seven days.

The same process can be performed for other thresholds (e.g., purity variations below or above 5%, such as 2%, 3%, and 4%).

In addition to the above tests, further tests were conducted to determine when 10 could be reached at a certain temperature^-6Sterility Assurance Level (SAL). SAL was determined according to the program USP 55 "Biological Indicators-Resistance performances Tests". Greater than or equal to 1,000,000 but less than 10,000,000 of the thermophilic fats testedGeobacillus spores were inserted into 1mL samples of preservative solution containing 70% v/v aqueous isopropanol and 2.0% w/v chlorhexidine gluconate. Samples were tested at 100 ℃, 105 ℃ and 110 ℃ for different durations. Ten samples were tested at each time point. The results are as follows:

TABLE 12- -sterility test results of SAL test

The above results are expressed as the number of positives recorded in the 10 samples tested. For example, "10" means that 10 of the 10 samples tested were microbiologically positive (non-sterile). The "D value" was then calculated according to the USP 55 program using the above data. The term D value has the usual meaning used in microbiology. In particular, it refers to a ten fold reduction in time and is the time required to kill 90% of the organisms under study at a certain temperature. Thus, after a 1D colony reduction, only 10% of the original organisms remain, i.e. the population number is reduced by one decimal place in the enumeration protocol. D values can be calculated using the Holcomb-Spearman-Karber method (HSK), a method of data analysis known in the art (see USP 55 products and Block, Seymour S. "Disinfection, Sterilization, and Preservation." Philadelphia, PA: Lippincott Williams & Wilkens, 120-122.2001). Applying the HSK method to the data of table 12 above, the calculated D value and the upper and lower confidence limits:

TABLE 13 values of D

The D value can be used to calculate Sterility Assurance Level (SAL) (see USP 55 program). SAL is a term used in microbiology to describe the probability that an individual unit is non-sterile after it has been subjected to a sterilization process. 10^-6SAL means that there is an opportunity of 1/1000000 to retain a single viable microorganism in the sterilized article. By extrapolating the log reduction rate after extreme, artificially high initial contamination, the sterilization procedure must include 12 log increments (D value multiplied by 12), an overkill condition, to verify a SAL of 10^-6. Prudent, confidence upper bound D values are used to calculate up to 10 below^-6Time of SAL:

^-6TABLE 14 SAL10 time

Thus, as shown in table 14, exposing the preservative solution to a temperature of 100 ℃ for about 48.58 minutes, 105 ℃ for about 16.97 minutes, or 110 ℃ for about 6.17 minutes, would each have a 10^-6The SAL of (i.e., the opportunity of 1/1000000 for viable microorganisms to be present after the sterilization process).

Using standard mathematical modeling, the four D-value data points described above from table 14 were used to prepare an exponential prediction function having the formula:

y＝1,553,000,000·e^(-0.1747x) (I)

where y is the time in minutes and x is the temperature in degrees celsius. Thus, formula (I) indicates that at least 10 is reached at a given temperature^-6Minimum time of SAL. Using formula (I), the following predicted data points are generated:

^-6TABLE 15 predictive SAL10 time

The times shown in tables 14 and 15 were rounded as shown in table 16:

^-6TABLE 16 rounded SAL10 time

The rounded data points are plotted in figure 2. Figure 2 shows the sterilization time and temperature (the region between the curves) as a function of the parameter space (time and temperature) fitted to the trap to maintain a specific purity change after the sterilization process. The data points in fig. 2 include data points from tables 9 and 16 above. Black squares represent data points from 85 ℃ to 120 ℃, with corresponding times being sterile. Grey squares represent data points from 125 ℃ to 135 ℃, with corresponding times being sterile. The following natural logarithm formula is fitted to the square data points from 85 ℃ to 125 ℃:

for 1. ltoreq. x.ltoreq.552, y.6.14. ln x +123.2 (II)

Where y is the temperature in degrees celsius and x is the time in minutes. From 125 ℃ to 135 ℃ and time x is constant for 1 minute.

The data points shown in table 9 above are also plotted in fig. 1. Black diamonds represent data points from 85 ℃ to 135 ℃, with corresponding times having a percent change in purity of up to 5%. Black triangles represent data points from 85 ℃ to 135 ℃, with corresponding times having a percent change in purity of up to 4%. Black circles represent data points from 85 ℃ to 135 ℃, with corresponding times having a percent change in purity of up to 3%. The gray triangles represent data points from 90 ℃ to 135 ℃ with corresponding times having a percent change in purity of at most 2%. There was no time at 85 ℃ where the solution had a percent change in purity of at most 2%. The following natural logarithmic formula is fitted to the black diamond data points (i.e., points with up to 5% purity change):

for 9.1. ltoreq. x. ltoreq.1123, y 10.38. ln x +156.9 (III)

The following natural logarithmic formula is fitted to the black triangle data points (i.e., points with up to 4% purity change):

for 7.3. ltoreq. x.ltoreq.900, y-10.37. ln x +154.6 (IV)

Where y is the temperature in degrees celsius and x is the time in minutes. The following natural log formula is fitted to the black circle data points (i.e., points with up to 3% purity change):

for 5.5 ≦ x ≦ 670, y ≦ -10.4 · ln x +151.7 (V)

Where y is the temperature in degrees celsius and x is the time in minutes. The following natural logarithmic formula is fitted to the gray triangle data points (i.e., points with at most 2% purity change):

for x ≦ 3.7 ≦ 260, y ≦ -10.6 · ln x +148.3 (VI)

Where y is the temperature in degrees celsius and x is the time in minutes.

As can be seen from fig. 2, the region above formula (II) but below formula (III) within the temperature range of 85 ℃ to 125 ℃ represents the combination of temperature and time that provides a sterile solution with a variation of at most 5% purity. This area can be presented by the following relationship:

x is more than or equal to 1 and less than or equal to 552, and y is more than or equal to-6.14. ln x +123.2

And

x is not less than 21.5 and not more than 1123, y is not less than-10.38. ln x +156.9

Where y is the temperature in degrees celsius and x is the time in minutes. Similarly, the region above the constant line x ═ 1 and below formula (III) in the temperature range of 125 ℃ to 135 ℃ represents the temperature and time combination that provides a sterile solution with a variation in purity of at most 5%. This area can be presented by the following relationship:

x≥1

and

x is more than or equal to 9.1 and less than or equal to 21.5, y is more than or equal to-10.38. ln x +156.9

Where y is the temperature in degrees celsius and x is the time in minutes.

As can be seen from fig. 2, the region above formula (II) but below formula (IV) within the temperature range of 85 ℃ to 125 ℃ represents the combination of temperature and time that provides a sterile solution with a purity variation of at most 4%. This area can be represented by the following relationship:

x is more than or equal to 1 and less than or equal to 552, and y is more than or equal to-6.14. ln x +123.2

And

x is more than or equal to 17.5 and less than or equal to 900, y is more than or equal to minus 10.37. ln x +154.6

Where y is the temperature in degrees celsius and x is the time in minutes. Similarly, the region above the constant line x ═ 1 and below formula (IV) in the temperature range of 125 ℃ to 135 ℃ represents the temperature and time combination that provides a sterile solution with a change in purity of at most 4%. This area can be represented by the following relationship:

x≥1

and

x is more than or equal to 7.3 and less than or equal to 17.5, y is more than or equal to-10.37. ln x +154.6

Where y is the temperature in degrees celsius and x is the time in minutes.

As can be seen from fig. 2, the region above formula (II) but below formula (V) within the temperature range of 85 ℃ to 125 ℃ represents the combination of temperature and time that provides a sterile solution with a purity variation of at most 3%. This area can be represented by the following relationship:

x is more than or equal to 1 and less than or equal to 552, and y is more than or equal to-6.14. ln x +123.2

And

x is more than or equal to 13 and less than or equal to 670, and y is more than or equal to-10.4. ln x +151.7

Where y is the temperature in degrees celsius and x is the time in minutes. Likewise, the region above the constant line x ═ 1 and below formula (V) in the temperature range of 125 ℃ to 135 ℃ represents the temperature and time combination that provides a sterile solution with a change in purity of at most 3%. This area can be represented by the following relationship:

x≥1

and

for x is more than or equal to 5.5 and less than or equal to 13, y is more than or equal to minus 10.4. ln x +151.7,

where y is the temperature in degrees celsius and x is the time in minutes.

As can be seen from fig. 2, the region above formula (II) but below formula (VI) within the temperature range of 90 ℃ to 125 ℃ represents the combination of temperature and time that provides a sterile solution with a purity variation of at most 2%. This area can be represented by the following relationship:

x is more than or equal to 1 and less than or equal to 552, and y is more than or equal to-6.14. ln x +123.2

And

x is more than or equal to 9 and less than or equal to 260, y is more than or equal to minus 10.6. ln x +148.3

Where y is the temperature in degrees celsius and x is the time in minutes. Similarly, the region above the constant line x ═ 1 and below formula (VI) in the temperature range of 125 ℃ to 135 ℃ represents the temperature and time combination that provides a sterile solution with a change in purity of at most 2%. This area can be represented by the following relationship:

x≥1

and

x is more than or equal to 3.7 and less than or equal to 9, y is more than or equal to minus 10.6. ln x +148.3

Where y is the temperature in degrees celsius and x is the time in minutes.

While aspects of the present invention have been described in connection with the exemplary embodiments, it will be understood by those skilled in the art that variations and modifications of the aspects described above may be made without departing from the scope of the invention. Other variations will be apparent to those skilled in the art from consideration of the specification or practice of the disclosure herein.