Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Biocides; animal or insect repellents or attractants
Reexamination Certificate
1999-04-22
2003-02-04
Travers, Russell (Department: 1617)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Biocides; animal or insect repellents or attractants
C514S714000, C422S028000, C422S029000
Reexamination Certificate
active
06514509
ABSTRACT:
This application claims foreign priority of Italy VR98A000033, filed Apr. 30, 1998.
BACKGROUND OF THE INVENTION
The present invention relates to a method for production on the spot of a peracetic acid (PAA) aqueous solution (disinfectant system) used for high-level chemical disinfection and chemical cold-sterilization of many devices, equipment and plants, e.g.
medical and surgical devices, including fiber-optic instruments (endoscopes, etc.), bed sheets or other fabrics used in the sanitary field (hospitals, surgeries, etc.);
tools, surfaces, instruments, CIP (cleaning in place) pipes, and objects in general in the field of food handling;
wastewater treatment plants;
and in any other field requiring a high-level disinfection or chemical cold-sterilization treatment.
Efficient sterilization methods are required for industrial and sanitary applications. For their repeated use, various tools and devices require safe, effective and fast disinfection and sterilization procedures. Although most “critical” multiple-use medical-surgical instruments are sterilized, after accurate cleaning, by:
dry heat treatment,
wet heat treatment (steam autoclave),
ethylene oxide sterilization (for plastics),
there are, however, devices (for example endoscopes, etc.), especially in the sanitary field, which are made of highly heat-sensitive material and thus cannot be subjected to the above treatments.
Moreover, since some of such devices are often used for diagnostic and therapeutic purposes in daily activity, their passage through ethylene oxide autoclaves, although being feasible, is impractical owing to both excessively high costs and time limits. Accordingly, high-level disinfection and sterilization with chemical products at room temperature is the only feasable procedure for such instruments.
Many “cold-sterilizing” compositions have been suggested so far, e.g. 2%, 2.5%, 3.2% glutaraldehyde, buffered to pH 7.5-8.5 upon being used, and the phenol-phenate buffer system in association with glutaraldehyde (Sporicidin™) or, more recently, “Sporicidin Plus™”, an association of phenol, phenolic derivatives and glutaraldehyde; see U.S. Pat. No. 4,103,001 (Schattner). All these products have in common the presence of glutaraldehyde and make it possible to obtain sterilization of the devices, but only after extremely long contact times.
A process or a product can be considered to be a sterilizer only if it can eliminate all microbial life forms, including spores, which have the highest resistance to sterilization processes. Accordingly, a sterilizing chemical preparation must be bactericidal, fungicidal, virucidal and sporicidal.
A relatively small number of antimicrobial agents is actually sporicidal and thus usable as “chemosterilizers”. One of them is peracetic acid, a peroxide agent, which has a wide and rapid germicidal activity. The FDA (Food and Drug Administration) has long recognized as 510 (k)-cleared chemical sterilization agents two products whose active principle is peracetic acid:
Steris 20™ (0.2% peracetic acid at 50-56° C. for 12 minutes of contact)
Peract 20™ (0.08% peracetic acid plus 1% hydrogen peroxide at 20° C. for 8 hours of contact).
The first product is a concentrated solution of 35% w/w peracetic acid, which has a six-month stability period. The second product is a ready-for-use acid aqueous solution, which has a stability period of one year.
Peracetic acid has the same attributes as hydrogen peroxide (germicidal and sterilizing capacities, non-dangerous decomposition products and infinite solubility in water), but is more soluble in lipids and insensitive to deactivation by catalase and peroxidase enzymes. It is also a more powerful antimicrobial agent than hydrogen peroxide, since it is rapidly active at low concentrations against a broad range of microorganisms. Furthermore, it is sporicidal at very low temperatures and remains effective even in the presence of organic material. As a weak acid it is more active in an acid environment.
Aqueous solutions of concentrated peracetic acid and hydrogen peroxide have already been proposed commercially; however, they have a very short stability period. A certain stability is ensured by the presence of an excess of acetic acid and/or hydrogen peroxide with respect to the equilibrium for solutions of peracetic acid ranging from 0.5% to 50% w/w. Moreover, the addition of a sequestrant for metallic ions to the aqueous solution, e.g. a diphosphonic acid and an anionic surfactant belonging to the class of alkylbenzene sulfonates, alkylsulfonates or alkane sulfonates, as disclosed in U.S. Pat. No. 4,051,058 (Bowing et al.), ensures further stability of the concentrated peracetic-acid aqueous solutions used to prepare diluted microbicidal solutions in a sanitary and food-handling environment. However, these concentrated solutions, when correctly preserved, can be considered as stable for up to six months without appreciable losses of active oxygen.
The “six month” term is highly penalizing from the commercial point of view, especially because it does not allow storage on an industrial scale (that is to say, storage in relevant amounts), and this has a negative effect on the final cost of peracetic acid (PAA).
In general, peroxides are high energy state compounds and as such can be considered to be thermodynamically unstable. Peracetic acid (PAA) is much less stable than hydrogen peroxide (HP). A 40% w/w solution of PAA loses 1 to 2% of its active ingredient per month, compared with hydrogen peroxide (30 to 90%), which loses less than 1% per year. The decomposition products of peracetic acid are acetic acid, hydrogen peroxide (HP), oxygen and water. Dilute solutions of peracetic acid are even less stable. Thus, for example, a 1% solution loses half of its concentration by hydrolysis in six days.
After succeeding in producing highly concentrated hydrogen peroxide, peracetic acid has been produced on an industrial scale by the reaction of acetic acid or acetic anhydride with concentrated hydrogen peroxide in the presence of sulfuric acid, which acts as a catalyst, as shown by the following reaction formula:
In order to prevent the inverse reaction, peracetic acid solutions are boosted with acetic acid and hydrogen peroxide (HP). Moreover, a stabilizing agent is used, e.g. a sequestrant (sodium pyrophosphate) or a chelating agent (8-hydroxyquinoline) to remove any trace of metallic ions, which would accelerate the decomposition of peroxides. A system in which use is made of anionic surfactants in PAA solutions has not only higher stability but also a higher antimicrobial activity—see U.S. Pat. No. 4,051,058. Finally, synergistic effects between PAA and ethyl alcohol or isopropyl alcohol have been noted in connection with germicidal activity.
Despite the various proposals as described above, when stable commercial peracetic acid is diluted with water it decomposes rapidly. Such a decomposition can be accelerated by high temperatures and the presence of heavy metals in the solution. Accordingly, it is advisable to dilute the peracetic acid with deionized or distilled water, store it in a cool place and use it as soon as possible. The decomposition of peracetic acid can occur in the three following manners:
Oxygen is formed in reaction (1). The rate of decomposition in this way depends on the nature and quantity of heavy metals in the solution. This reaction is often responsible for the loss of activity of insufficiently stabilized PAA solutions.
Reaction (2) proceeds via intermediate radicals. Methyl radicals may be formed among other substances. Similarly to reaction (1), also this reaction is catalyzed by metallic ions.
The hydrolysis of peracetic acid (reaction 3) is highly pH-dependent. It takes place whenever peracetic acid solutions are diluted. The reaction products are acetic acid and hydrogen peroxide.
Every dilution of commercially available PAA solutions results in a new equilibrium being reached between peracetic acid, acetic acid, hydrogen peroxide and water. Although it is possible to dilute solutions of peracetic acid, the conce
Farmec S.n.c. di Tabasso Renato & C.
Josif Albert
Modiano Guido
O'Byrne Daniel
Travers Russell
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