NZ204717A - Sporicidal compositions containing aldehydes and polyhydric substances - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £04717 204717 Priority Dete(s^: Complete Specification Filed: *27. ;Class: /Q&. ;lfVWl986 ;Publication Date: 7 ;P.O. Journal. No: ;y ;27 ;M DRASDSBS ;N'KVV ZliAl AN'I) ;I'ATliNTS ACT, I <>53 ;No.: ;Date: ;COMPLETE SPliCIFICATION IMPROVED SPORICIDAL COMPOSITIONS ;*/We, WHITE LEY CHEMICALS AUSTRALIA PTY. LTD., a Company incorporated under the laws of the State of New South Wales, Commonwealth of Australia, of 82-84 Ivy Street, Chippendale, New South Wales 2008, Australia,. hereby declare the invention for which ? / we pray that a patent may be granted to jpjt^k/us, and the method by which it is to be performed, to be particularly described in and by the follov/ing statement:- 2(154717 FIELD OF THE INVENTION This invention relates to improved sporicial compositions and to i.i methods for manufacture of such compositions. > I BACKGROUND OF THE INVENTION | i i.

The most wide spread method of sterilisation employs steam. j !• However, use of steam is not always convenient and is sometimes impractical, for example, when there is a requirement to sterilise : heat sensitive materials. Although a large number of chemical bac- ^ teriacides are known, there are few effective chemical sporicides. If | sporicidal action is required the most commonly used agents are for- i. maldehyde and alkaline glutaraldehyde solutions.

Formaldehyde in 1 to 2% solution requires up to 20 hours to j destroy spores. A shorter time is required if a higher concentration | i of formaldehyde in isopropyl alcohol is employed. The usefulness of \ formaldehyde is, however, limited by its irritating fumes and | toxicity. | R.E. Pepper and E .R. Lieberman (U.S. Pat. 3016328) found that 2% J W/W glutaraldehyde solutions are effective when buffered in the pH | range of 7.5 to 8.5 by use of a mildly alkaline substance such as | | sodium bicarbonate, and that Gluteraldehyude solutions as sold commer- | cially are mildly acid and do not exhibit sporicidal activity below pH |, 7.5. Pepper et al has disclosed that at pH greater than 8.5 there is a tendency for polymerization to proceed so rapidly that shelf life of ! alkaline glutaraldehyde solutions is reduced beyond practical limits. ; Solubility parameters of the system limited the amount of alkilinating ; i agent which would dissolve and a lower alkanol j 204717 was generally required for the purpose of dissolving sufficient of the akilinating agent required to obtain an effective pH of above 7.4.

Stonehill (US 3282775) showed that bacteriacidal and sporicidal activity could be obtained by combination of glutaraldehyde with cationic surfactants at pH4-pH9 while Boucher (US 3968248) showed a synergistic effect between certain non-ionic surfactants with glutaraldehyde under acid conditions.

The latter preparations disclosed by Boucher had the significant advantage that a ready to use 2% W/W glutaraldehyde preparation could be offered for commercial sale which was stable for periods of up to three years, which did not require dilution by the user and which could be heated to about 75°C to speed biocidal action without unduly promoting decomposition or polymerization. Boucher pointed out that in a few instances it could be of interest to use as a diluent not only filtered de-ionized water but a lower alkanol such as methanol, ethanol or isopropanol.

A serious practical disadvantage of all the foregoing sporicidal compositions is their odour and irritancy to the human skin and mucous membranes. The unpleasant aldehyde vapours emitted both during manufacture and use of the foregoing composition can pose a significant environmental problem.

DISCLOSURE OF THE INVENTION The present invention stems from the discovery that when certain common aldehydes are combined with diethylene glycol triethylene glycol and higher molecular weight glycols containing multiple ethoxy (-CH2-CH20-) groups under acid condition there may be formed a product which is sporicidally active and which are substantially - odour free at a normal working dilution of the solution containing 0.1 to 2.5 per cent by weight of glutaraldehyde. 204 717 In practice sterilizing solutions are usually used at a dilution such that the solution contains from 0.05» W/W to 5% W/W of the aldehyde and a normal working dilution would contain 2% W/W of aldehyde.

The formation of such a product is surprising since on the one hand aldehydes which are sporicidal typically emit odours which are unpleasant, obnoxious and potentially toxic to occupants of closed rooms or operating theatres in which they have been used whereas, on the other hand hemiacetals which may be formed by reaction of an aldehyde and an alcohol are not sporicidal at pH 7.0 and lower and are generally odourless or of low odour.

It is believed that the obtained benefit results from the formation of a complex comprising a hydrogen bonded linkage between car-bonyl and hydrozyl groups most likely a precursor to the formation of a hemiacetal and which exists in an equilibrium with the hemiacetal in the pH range 3-7.5, stability of the complex being influenced in accordance with selection of the aldehyde, polyhydric substances, and pH.

It is thought that this complex has a lower vapour pressure than the free aldehyde and therefore reduces the odour of the solution. The ability to prepare substantially odourless, effective, aldehyde preparations is considered an advantage which will greatly extend their usefulness as sporicidal agents and will improve safety.

According to one aspect the invention consists in a sterilizing composition comprising a solution containing the reaction product of a mono of dialdehyde and diethylene glycol, triethylene glycol and gly-colethus having a molecular weight of less than 500, the pH of said solution being selected within the range of from pH 3.5 to pH 7.0 so that the composition is sporicidal and so that the solution is substantially free of odour when at a dilution 204717 equivalent to less than 2.5 parts by weight of aldehyde to 100 parts by weight of water.

According to a second aspect the invention consists in a method of preparing a sporicidal solution comprising the steps of: 1. combining a mono or dialdehyde with a polyhydric substance such as diethylene glycol, triethylene glycol or similar diethoxy glycol ethers. 2. adjusting the pH within the range of from pH 3.5 to pH 7.0 for a time and at a temperature sufficient to form a product which is sporicidal and which is substantially odour free when at a dilution equivalent to less than 2.5 parts by weight of aldehyde to 100 parts by wei ght of solution.

It will be understood that sterilizing compositions according to the invention may have a concentration of aldehyde greater than 2.5 parts by weight for 100 parts by weight of water and in such concentrated solutions may not be odour free, the test being that when diluted to normal working strength the solution shall be substantially odour free.

PREFERRED EMBODIMENTS OF THE INVENTION Various embodiments of the invention will now be further described by way of illustration only and with reference to various examples. The aldehyde may be a monoaldehyde or a saturated dialdehyde or a mixture thereof and preferably is a saturated dialdehyde of from 2 to 6 carbon atoms; for example malonaldehyde, succinaldehyde, glyoxal, or adipaldehyde. However for preference the aldehyde is formaldehyde or glutaraldehyde and glutaraldehyde is the most highly preferred. The polyhydric substances is preferably a polyol such as 204717 polyethylene glycol, triethylene glycol or diethylene glycol.

The complex is formed by adjusting pH within the range of pH 3.5 pH 7.5 by the addition of a strong acid such as hydrochloric acid, or phosphoric acid or mono or dicarboxylic acid. The choice of acid and pH depends on the stability of the other components. The complex of the present invention is stable under acid conditions and up to a pH of 7.0, the extent of stability varying in accordance with the aldehyde and the glycol substance at pH below 3.5 there is a tendency to hemiacetal formation. The formation of the complex may be assisted by raising the temperature of the solution for a time which varies with the temperature and pH. Typically the complex is formed at temperature of from 5°C to 100°C over periods ranging from 5 seconds (at the higher temperature) to 24 hours (at the lower temperature).

It will be understood that aldehydes react with alcohols and glycols to form an equilibrium with the hemiacetal under acid conditions.

Since the hemiacetal has little or no sporicidal activity it is important to form the product without formation of the hemiacetal to any si gni ficant degree.

The resulting complexes while strongly antimicrobial ly active in their own right can also, in some instances, be mixed with other compatible chemical groups of commercially available antimicrobials, e.g. quaternary ammonium, phenolic, chlorphenolic and organotin to give further enhancement in antimicrobial properties of the end products for specialised medical and industrial purposes. An especially suitable addition is Benzalkonium chloride BP. 2047I7 It is desirable to add a surfactant for preference a non-ionic surfactant and most desirably Tergitol 15-S-12 made by Union Carbide Inc. , U.S.A..

The following are examples of preparations according to 'the invention.

EXAMPLE 1 40.0 grams of 25% w/w medical grade glutaraldehyde supplied by Union Carbide Inc., U.S.A. were mixed with 60.0 grams of triethylene glycol, the pH was adjusted to 5.5 and the solution heated to 100°C for 1 minute. The mixture was then cooled to room temperature when 1.0 gram of Tergitol 15-S-12 was added. The product had a faint odour of glutaraldehyde when cooled which disappeared when diluted with tap water to normal use strength namely 0.1 - 2.5% w/w glutaraldehyde.

EXAMPLE 2 40.0 grams of 25"i w/w medical grade glutaraldehyde were mixed with 60.0 grams of triethylene glycol, pH was adjusted to pK 4.5 ana the mixture allowed to stand at room temperature (20°C) for 1 hour. To this mixture was then added 1.0 gram of Tergitol 15-S-12. The mixture had a faint odour cf glutaraldehyde which disappeared when diluted to use strength namely 3-1 - 2.5% w/w glutaraldehyde.

EXAMPLE 3 40.0 grams of 25% w/w medical grade glutaraldehyde were mixed with 60.0 grams of ethylene glycol, pH was adjusted to 4.0 and the solution allowed to stand at room temperature (20°c) fro 2 hours. To this mixture was then added 1 gram 204717 of Tergitol 15-S-12. The product yielded had similar odour properties to those yielded by EXAMPLES 1 and 2. The solution was then diluted prior to use with an aqueous solution containing 70% by volume of ethanol . 40.0 grams of 25X w/w grade glutaraldehyde were mixed with 6.0 grams of sorbitol dissolved in an equal weight of water at pH 3.5. The solution was allowed to stand for 24 hours. To this solution was then added 1.0 gram of Tergitol 15-S-12. The product yielded had similar odour properties to those yielded in EXAMPLES 1 and 2.

In order to confirm that an antimicrobial 1y active complex can be formed over a wide variety of temperature conditions the products of EXAMPLES 1 and 2 were tested by the T.G.A. Disinfectant Test, Option B, Australian Journal of Hospital Pharmacy Volume 8, No. 4, 1978, with the following results against the four nominated pathogenic bacteria as follows - EXAMPLE 4 Escherichia Coli NCTC 8196 Pseudomonas aeruginosa NCTC 6749 Proteum vulgaris NCTC 4635 Staphylococcus aureus NCTC 4163 204717 TESTED FIRST DAY DILUTION 1 in 40 (2.5% v/v) EXAMPLE 1 Test No.l Test No.2 Test No.I Test No.2 Ps aeruginosa ----- _____ +____ •S. aureus _____ _____ _____ _____ E. coli _____ +++++ _____ _____ P. vulgaris +++++ +____ _____ _____ REPEAT TESTED SECOND DAY DILUTION I in 40 (2.5% v/v) Ps aeruginosa ----- _____ _____ „____ S. aureus _____ _____ _____ _____ E. coli, _____ _____ ___________ P. vulgaris _____ 4. + + + + + + + + + _____ REPEAT TESTED THIRD DAY DILUTION 1 in 40 (2.5% v/v) Ps aeruginosa _____ _____ _____ _____ When interpreted within the statistical expectations of this test the products made by EXAMPLES 1 and 2 show identical antimicrobial perforinance. These tests show that both the products of EXAMPLES 1 and 2 have a limiting effective concentration of slightly greater than 0.25% w/w glutaraldehyde when tested under the conditions of the T.G.A. Disinfectant Test, wherein the active biocide is challenged with a heavy load of yeast cells, conditions proven to be a reasonable and statistically valid representation of a highly contaminated cleaning solution found in a normal hospital environment.

This latter observation was duly vertified when the same tests were repeated at a level of 0.33% w/w glutaraldehyde. At this concentration sterility was achieved in each tube of

Claims (13)

204717 each test against the four bacteria over a consecutive three day peri od. That the same antimicrobial performance was noted when each product was diluted to 0.25% w/w glutaraldehyde clearly establishes the formation of a consistent chemical complex over a wide range of temperatures. When evaluated for sporicidalperformance using spores of Bacillus subtil is according to AOAC Sporicidal Test Procedure, a solution containing 1.0 per cent glutaraldehyde made by EXAMPLE 2 was demonstrated to achieve sterility in 10 hours at 25°C. This level of sporicidal performance compares favourably with dilute glutaraldehyde preparations as disclosed by Pepper, Stonehill and Boucher. Other odourless diocides such as ortho phenyl phenol and 2 chloro, 2 nitro 1,3 propane diol can be incorporated in such complexes by the addition of small quantities of lower alkanols e.g. ethanol with beneficial results. -10- 204717 WHAT ME CLAIM IS:

1. A sterilizing composition comprising a solution containing the reaction product of a mono or dialdehyde and diethylene glycol, triethylene glycol or a glycol ether having a molecular weight of less than 500, the pH of said solution being adjusted to within the range of from pH 3.5 to pH 7.5 so that the composition is sporicidal and so that the solution is substantially free of odour when at a dilution equivalent to less than 2.5 parts by weight of aldehyde to 100 parts by weight of water.

2. A composition according to claim 1 wherein the solution is substantially odour free when at a dilution equivalent to less than 2 parts by weight of aldehyde to 100 parts by weight of water.

3. A composition according to claim 1 or claim 2 further comprising a nonionic or anionic surfactant.

4. A composition according to any one of the preceding claims wherein the aldehyde is glutaraldehyde.

5. A composition according to any one of the preceding claims wherein either diethylene glycol or triethylene glycol is used.

6. A composition according to any one of the preceding claims wherein the reaction product is adjusted to a pH of between 3.5 and 7.5 by addition of an acid selected from the group comprising hydrochloric, phosphoric and a mono or dicarboxylic acid.

7. A composition according to any one of the preceding claims whereof the sporicidal activity is enhanced by addition of a quaternary ammonium antimicrobial substance.

8. A composition according to claim 1 and substantially as herein described with reference to any one of the examples. -11- 2047"?

9. A method of sterilization comprising the step of bringing an article to be sterilized into contact with a solution according to any one of claims 1 to 8 for an effective time.

10. A method of preparing a sporicidal solution comprising the steps of: (i) reacting a mono or dialdehyde with diethylene glycol, triethylene glycol or glycol ethers having a molecular weight of less than 500. and (ii) adjusting the pH within the range of from pH 3.5 to pH 7.5 for a time and at a temperature sufficient to form a product which 1s sporicidal and which is substantially odour free when at a dilution equivalent to less than 2.5 parts by weight of aldehyde to 100 parts by weight of solution.

11. A composition made according to the method of claim 10 when substantially odour free when at a dilution equivalent to less than 2 parts by weight of aldehyde to 100 parts by weight of solution.

12. A composition according to any one of claims 1 to 8 and 11 which is diluted with an aqueous lower alkanol solution containing 15 to 70 per cent by volume of either methanol, ethanol or isopropanol.

13. A method according to claim 10 for substantially as hereinbefore described with reference to any one of the examples.