Ph controlled antimicrobial formulation

Abstract: The present invention is a unique antimicrobial composition which comprises an antimicrobial agent, a nonionic surfactant and an anionic surfactant. The composition is useful in providing antimicrobial effectiveness in surgical scrub applications with excellent mildness characteristics.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to antimicrobial formulations for providing antimicrobial effectiveness to the skin without irritation or dryness. The formulations, comprising parachlorometaxylenol, are particularly useful in the health care profession such as in surgical practice as a pre-operative scrub. 2. Description of Related Art Effective antiseptic or disinfectant compositions can be formed by combining a surfactant or detergent with an antimicrobial agent. Thus, antiseptic cleaning compounds can be formulated rather easily; however, many such compositions are not suitable for use in contact with human skin due to the abrasive nature of the surfactant-containing composition, and there are surfactants incompatible with many antimicrobial agents. Where the composition is intended for use as surgical scrub, mildness is an important consideration. Mildness indicates the composition does not cause excessive irritation of the skin, such as erythema. In a majority of cases, skin irritation can be attributed to contact of the skin with a surfactant. It is believed that skin irritation results partly due to the nature of the surfactant itself and, in part, due to the action of the surfactant in weakening the resistance of the skin. The degree of irritation may vary significantly with the surfactant, the individual user, the length of contact and the conditions of contact. In many cases the degree of irritation is also affected by the combination of the antimicrobial agent and the surfactant. It is believed that surfactants have a denaturing effect on the skin. Thus, antimicrobial agents or chemicals which normally do not irritate the skin when combined with a surfactant can penetrate or be readily absorbed by the skin and cause irritation. The absorption of antimicrobial agents or chemicals by the skin is generally undesirable. Surgical scrub procedures and techniques are highly conducive to the development of erythema and other irritations. All personnel involved in surgical procedures use a surgical scrub in preparation for surgery. Frequently, the same individual will scrub three to five times on a single day. A typical surgical scrub involves placing a cleansing composition on the hand. Commonly, a brush or sponge is used and the arms from the elbows to the fingertips are scrubbed thoroughly for as long as ten minutes. Thus, the epidermal layers of the skin are subject to significant rubbing and aggravation. After the arms and hands have been scrubbed they are rinsed, dried and placed into rubber gloves. The rinse is often not complete and residual surfactant and/or antimicrobial compounds from the cleansing composition are left on the skin. Many times, the hands remain gloved for as long as six hours. During this time the hand perspires and the pores can open and enlarge, thereby allowing residual surfactants and/or antimicrobial compounds to penetrate the skin. This in turn can create topical skin irritations. The likelihood of irritation or erythema increases with the frequency one performs the surgical scrub procedure. It is important that surgical scrub compositions be very mild, but yet effective. Numerous attempts have been made to develop formulations containing antimicrobial agents and surfactants, which reduce or eliminate skin irritation and provide effective antiseptic or disinfectant properties. However, the efficacy of antiseptic or disinfectant compositions is greatly influenced by a number of variables, including pH, temperature, concentration of organisms, duration of exposure, concentration of the antiseptic and the type of surfactants used in the formulation. Formulations containing the antimicrobial agent, chlorhexidine, have been used as antibacterial skin cleaners in surgical scrubs. Formulations containing chlorhexidine generally include a, surfactant and a low percentage of an alcohol such as isopropanol. Billany et al., U.S. Patent No. 3,960,745, discloses a chlorhexidine cleansing composition formulated with a polyoxyethylene-polyoxypropylene nonionic surfactant. The formulation is commercially available as HIBICLENS® (trademark of ICI Americas, Inc.) sold by Stuart Pharmaceuticals, Wilmington, Delaware. Billany et al. discloses that anionic surfactants are not desirable surfactants because they may destroy the antibacterial activity of chlorhexidine solutions by complexing with the cationic chlorhexidine. Cationic surfactants are also not desirable because of their irritancy, and because, in combination with a soluble chlorhexidine salt, double decomposition can occur with the formation of insoluble chlorhexidine salts and consequent loss of antibacterial activity. Equally unsuitable surfactants for use in such formulations are amphoteric surfactants, which contain either anionic or cationic centers, depending upon pH, and they suffer from the above-described disadvantages of anionic and cationic surfactants. Other formulations have used bisbiguanide as an antimicrobial agent as disclosed in U.S. Patent No. 4,456,543 to Ownes. Ownes discloses an antibacterial cleansing formulation containing bisbiguanide and one or more nonionic polyoxyalkylene surfactants. Dewar et al., U.S. Patent No. 4,157,977 discloses surfactant-germicide compositions containing an antimicrobial active phenolic derivative in combination with hydroxyacetic acid and a surfactant. Casey et al., U.S. Patent No. 4,252,665 discloses a disinfectant cleaning composition containing ortho-benzyl-para-chlorophenol, anionic surfactants and sulfobetaine surfactants. Langguth et al., U.S. Patent No. 4,257,907 discloses disinfectant cleaning compositions containing ortho-benzyl-para-chlorophenol, sulfobetaine surfactants and anionic surfactants. White, European Patent Application 0 223 681, discloses an alcohol-based antimicrobial composition. Meldovanyl et al., United Kingdom Application 2 203 339, and EP-A-0 397 218 disclose microbicidal formulations containing antimicrobial agents and surfactants. Formulations containing a germicidal phenol and a dispersant are known from FR-A-1,090,033 and FR-A-1,147,984. Formulations containing the antimicrobial agent parachlorometaxylenol (PCMX) have been developed as disclosed in U.S. Patent No. 4,632,772 to Garabedian et al. said Patent discloses an antimicrobial composition containing the active antimicrobial agent PCMX and an ionic surfactant, alkyl aryl ethoxylated sulfonate. Melvin, U.S. Patent No. 3,326,808 discloses an antiseptic surfactant composition containing PCMX and an anionic surfactant, the sodium salt of 2-sulfomethyl myristate. PCMX, being phenolic in nature with acidic hydrogen and insoluble in water, reacts with bases to form salts: PCMX exists in the salt form in solutions at higher pH and in the phenolic state at lower pH. Therefore, efficacy of the PCMX formulation is greatly influenced by pH. The efficacy of PCMX is also compromised by other factors such as solubility and the formation of an association complex with other components in a formulation. PCMX is related to other phenolic compounds such as cresol, carbolic acid, and hexachlorophene and has a characteristic phenolic odor. Other names for PCMX include chloroxylenol; 4-chloro-3, 5-xylenol; 4-chloro-3, 5-dimethylphenol, 2-chloro-m-xylenol; 2-chloro-5-hydroxy -m-xylene; 2-5-hydroxy-m-xylene; 2-chloro-5-hydroxy-1, 3-dimethylbenzene; 4-chlor-1-hydroxy-3, 5-dimethyl benzene; and 3,5-dimethyl-4-chlorophenol. PCMX is a desirable antimicrobial agent having sixty times the antimicrobial activity of other phenolics against a variety of gram-positive and gram-negative bacteria as reported by Windholz, M(ed). The Merck Index: An Encyclopedia of Chemicals and Drugs, ed 9. Rahway, NJ, Merck and Co., 1976. However, as reported by Ray et al., "Microbiological Evaluation of PCMX Complexes." J. Pharmacol Sci. 57:609-613 (1968), PCMX will react with various nonionic macromolecules such as polyethylene glycol, methyl-cellulose and polysorbate to form association complexes and therefore diminish the inhibiting and bactericidal activity of PCMX. Furthermore, as disclosed in U.S. Patent No. 4,326,977 to Schmolka, the efficacy of antiseptic compositions may be influenced by the type of surfactants used because some surfactants are incompatible with many antiseptic agents. Therefore, due to the antimicrobial activity of PCMX, it is desirable to have a PCMX formulation which provides substantially maximized efficacy and does not promote dryness or irritation to the skin. However, such a formulation is difficult to produce due to the incompatibility of many surfactants with many antiseptic agents like PCMX. SUMMARY OF THE INVENTION The present invention provides an antimicrobial composition comprising: (a) parachlorometaxylenol in an amount from 1.5 to 3.5 weight percent of the total composition; (b) polyoxypropylene-polyoxyethylene block copolymer in an amount from 1.0 to 6.0 weight percent of the total composition; (c) an ammonium salt of sulfated nonylphenoxypoly(ethyleneoxy) ethanol in an amount from 2.0 to 12.0 weight percent of the total composition; (d) ammonium lauryl sulfosuccinate in an amount from 2.0 to 12.0 weight percent of the total composition; (e) lanolin, a derivative of lanolin, aloe vera and/or isopropyl palmitate in an amount from 5.0 to 15.0 weight percent of the total composition; (f) hydroxypropyl methyl-cellulose or 2-hydroxyethyl-cellulose in an amount from 0.1 to 1.0 weight percent of the total composition; (g) an acid to adjust the pH in the range of from 4.0 to 6.0; and (h) the balance water. The antimicrobial composition of the present invention is useful in providing substantial antimicrobial effectiveness and substantial non-irritancy to the skin. Another attribute of the antimicrobial compositions is their ability not to dry the skin. A most significant advantage of the antimicrobial compositions is their use in the health care profession as effective surgical scrubs. An advantage of the antimicrobial compositions is that they provide substantial bactericidal effectiveness. In particular, they provide bactericidal effectiveness with respect to Staphylococcus aureus, Candida albicans , Pseudomonas aeruginosa, Escherichia coli and the like. Further advantages of the antimicrobial compositions of the present invention is their significant foaming properties, good solubility in water and adequate detergency. A further advantage of the antimicrobial compositions is that the components do not readily penetrate or are not readily absorbed by the skin. An advantage of the antimicrobial composition is a unique cidal PCMX formulation. The combination of a particular anionic surfactant being an ammonium salt of sulfated nonylphenoxypoly(ethyleneoxy) ethanol and a particular nonionic surfactant, being a polyoxypropylene-polyoxyethylene block copolymer, in proper proportion will solubilize PCMX completely and will not form an association complex. The composition provides substantial antimicrobial effectiveness and substantial non-irritancy to the skin. The active antimicrobial agent in the antimicrobial composition is parachlorometaxylenol (PCMX). The efficacy of PCMX is greatly influenced by pH. PCMX melts at 115°C and boils at 245°C. It is soluble in alcohol, ether, benzene, fixed oils, terpenes, and solutions of alkali hydroxides and is volatile with steam. PCMX is present in the antimicrobial composition in an amount from 1.5% to 3.5%, and preferably at 3.2%. The polyoxypropylene-polyoxyethylene block copolymer (hereinafter "nonionic surfactant") for the antimicrobial composition includes block copolymers whose various grades fall into a molecular weight range between 1000 to over 15,000. Suitable block copolymers for the antimicrobial composition are PLURONIC® polyols (trademark of BASF, Wyandotte Corp., Wyandotte, Michigan; CAS registry no.: 9003-11-6). Particular PLURONIC® polyols that are useful include, but are not limited to: L31, L35, F38, L43, L42, L62, L63, L64, P65, F68, L72, P75, F77, P84, P85, F87 and F88. A desirable PLURONIC® polyol in the antimicrobial composition is L64. PLURONIC® polyol L64 limits the formation of an association complex between the surfactants and the antimicrobial agent in the composition. The approximate molecular weight of PLURONIC® polyol L64 is 2900. The nonionic surfactant is present in the antimicrobial composition in an amount from 1.0% to 6.0% and preferably at 3.0% weight percent. It is believed that the appropriate effective amount of nonionic surfactant in the antimicrobial composition is important because the nonionic surfactant is capable of stabilizing and solubilizing PCMX in solution so as to enhance and maximize the antimicrobial activity of the antimicrobial composition. If the appropriate effective amount of nonionic surfactant is not used, the antimicrobial properties of PCMX may be weakened. A suitable ammonium salt of sulfated nonylphenoxypoly(ethyleneoxy)ethanol (hereinafter "anionic surfactant") for the antimicrobial composition is ALIPAL® CO-436 (trademark of GAF, Wayne, NJ) sold by GAF. The anionic surfactant is present in the antimicrobial composition in an amount from 2.0% to 12.0% and preferably at 8.0%. The anionic surfactant should preferably be used in the antimicrobial composition in an amount sufficient to maintain detergent action and so as not to adversely effect the active antimicrobial properties of the antimicrobial composition. In particular, it is not desirable for the anionic surfactant to complex with the antimicrobial agent. The ammonium lauryl sulfosuccinate (hereinafter "foam builder") enhances the foamability of the surfactants in the formulation. A preferred foam builder for the antimicrobial composition is MONAMATE® LNT-40 (a trademark of MONA Industries, Paterson, NJ) sold by MONA. The foam builder is present in the antimicrobial composition in an amount from 2.0 % to 12.0 % and preferably at 8.0 %. The function of the lanolin, the derivative of lanolin, the aloe vera and/or isopropyl palmitate (hereinafter "moisturizer and/or emollient") in the antimicrobial composition is to replace the natural skin oils which are lost or at least, partially removed by the cleansing action of the surfactants in the antimicrobial composition. Therefore chapping of the skin may be prevented. In addition, they also function to dissolve and maintain the oil-soluble antiseptics in the emulsion. Suitable derivatives of lanolin are the ethoxylated, acetylated alcohol and surface active alcohol derivatives of lanolin. A preferable moisturizer and/or emollient for the antimicrobial composition is an ethoxylated (75 moles) lanolin, SOLULAN®75 (trademark of Amerchol Corporation, Edison, NJ) sold by Amerchol Corporation. Another preferred moisturizer and/or emollient for the antimicrobial composition is an aloe vera or an ester comprising isopropyl palmitate and lanolin oil, ISOPROPYLAN® 50 (trademark of Amerchol Corporation, Edison, NJ) sold by Amerchol Corporation. Another preferred moisturizer and/or emollient for the antimicrobial composition is a polyethyl glycol lanolin derivative, PEG®75 lanolin (trademark of Amerchol Corporation, Edison, N.J.) sold by Amerchol Corporation. The combination of moisturizers and/or emollients is present in the antimicrobial composition in an amount from 5.0 % to 15.0 % and prefererably at 11.2 %. The hydroxypropyl methyl-cellulose and 2-hydroxyethyl cellulose (hereinafter "thickener") are additives that increases the viscosity and stability of a formulation. It is believed that the thickener provides a clear composition and improves activity of the composition. The preferred 2hydroxyethyl-cellulose (cellulose, 2-hydroxyethyl ether) thickener for the antimicrobial composition is CELLUSIZE® (trademark of Union Carbide, Danbury, CT) sold by Union Carbide, and the preferred hydroxypropyl methyl-cellulose thickener for the antimicrobial composition is METHOCEL® 40100 (a trademark of Dow Chemical, U.S.A., Midland, MI) sold by Dow Chemical. METHOCEL® thickener is 91 % hydroxypropyl methyl-cellulose which dissolves in water, is nonionic and is a highly efficient water retention agent. The thickener is present in the antimicrobial composition in an amount form 0.1 % to 1.0 % and preferably at 0.5 %. The antimicrobial formulation is adjusted to a pH within the range from 4.0 % to 6.0 %, preferably the pH is within the range of 4.0 % to 5.0 %, so the composition is compatible with the pH of skin and to avoid unnecessary irritation to the skin. Suitable acids include hydrochloric acid, sulfuric acid, phosphoric acid, citric acid, lactic acid, and gluconic acid. The balance of the antimicrobial composition is water. The water may be present in the antimicrobial composition in an amount from 60.0% to 85.0%. Other ingredients which are conventional or desirable in various cosmetic formulations may also be added to the antimicrobial composition as long as they do not adversely affect the overall properties of the antimicrobial composition. If desired, the antimicrobial composition of the invention may include a perfume to provide a pleasing scent or a dye to provide a characteristic color. The antimicrobial compositions of the present invention may be found to be highly effective against common microorganisms such as Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans and Escherichia coli. It is recognized, however, that the effectiveness of the antimicrobial composition depends upon the particular combination of materials, the concentration of ingredients used and the nature of the particular microorganism. Generally, the composition may be in liquid form but may also be in the form of a gel or ointment. EXAMPLE I FORMATION OF AN ANTIMICROBIAL COMPOSITION An antimicrobial composition was made by mixing in a suitably sized vessel, for a sufficient amount of time to insure homogeneity, to form a solution A, the following ingredients: INGREDIENTS WT PERCENT Polyoxyethylene polyoxypropylene condensates 3.0 Sulfated nonylphenol ethoxylates 8.0 Propylene glycol 6.0 PEG-75 Lanolin 4.0 Ammonium lauryl sulfosuccinate 8.0 Aloe Vera 0.2 Isopropyl Palmitate Lanolin Oil 1.0 Parachlorometaxylenol 3.2 In a separate vessel, a solution B of 0.5% of hydroxylpropyl methylcellulose, 65.3% of deionized water and 0.5% of ethylenediamine tetraacetic acid (EDTA) was mixed for 60 minutes until all of the hydroxylpropyl methylcellulose was dissolved and no evidence of granulation remained. Solutions A and B were then mixed together thoroughly for 60 minutes and during the mixing, 0.30% of fragrance was added. Then 0.5% of 6 N hydrochloric acid and 0.5% of 5 N sodium hydroxide were added to adjust the pH to 4.5. The solution was then left without agitation for 12 hours until the solution became clear. EXAMPLE II FORMATION OF AN ANTIMICROBIAL COMPOSITION An antimicrobial composition was made by mixing in a suitably sized vessel for a sufficient amount of time to insure homogeneity, to form a solution A, the following ingredients: INGREDIENTS WT PERCENT Polyoxyethylene polyoxypropylene condensates 3.0 Sulfated nonylphenol ethoxylates 8.0 Propylene glycol 6.0 PEG-75 Lanolin 4.0 Ammonium lauryl sulfosuccinate 8.0 Aloe Vera 0.2 Isopropyl Palmitate Lanolin Oil 1.0 Parachlorometaxylenol 3.2 In a separate vessel, a solution B of 0.5% of hydroxylpropyl methylcellulose and 65.8% of deionized water was mixed for 60 minutes until all of the hydroxylpropyl methylcellulose was dissolved and no evidence of granulation remained. Solutions A and B were then mixed together thoroughly for 60 minutes and during the mixing, 0.30% of fragrance was added. Then 0.5% of 6N hydrochloric acid and 0.5% of 5N sodium hydroxide were added to adjust the pH to 4.5. The solution was then left without agitation for 12 hours until the solution became clear. EXAMPLE III COMPARATIVE ANALYSIS OF RELATED ANTIMICROBIAL COMPOSITION TO THE ANTIMICROBIAL COMPOSITIONS OF THE PRESENT INVENTION Testing was conducted to compare the efficacy of the antimicrobial composition of U.S. Patent No. 4,632,772 to Garabedian et al. to the antimicrobial composition of the present invention. Samples from Examples I and II above, designated as A and B respectively, were compared to the commercially available antimicrobial composition of Garabedian et al., ULTRADEX® (trademark of Dexide, Inc., Fortworth, Texas) which contains 3.0% PCMX, designated as C in the following table. Full strength compositions of A, B and C were serially diluted 1:10 and 1:100. Each dilution was challenged with 0.1 ml of inoculum containing the number of colony forming units (CFU) of the following organisms, Staphylococcus aureus, Pseudomonas aeruginosa , Candida albicans and Escherichia coli. The results are reported in Table II below showing the kill times in minutes. KILL TIMES (Minutes) ORGANISM DILUTIONS A B C 1. Staphylococcus aureus Full 5 minute 1 minute 1 minute 4.0X10 6 CFU 1:10 1 minute 1 minute Positive 1:100 Positive 5 minute Positive 2. Pseudomonas aeruginosa Full 1 minute 1 minute 1 minute 1.6X10 7 CFU 1:10 1 minute 5 minute Positive 1:100 Positive Positive Positive 3. Candida albicans Full 1 minute 1 minute 1 minute 1.9X10 5 CFU 1:10 5 minute 5 minute 1 minute 1:100 Positive Positive Positive 4. Escherichia coli Full 1 minute 1 minute 1 minute 3.2X10 7 CFU 1:10 1 minute 5 minute Positive 1:100 Positive Positive Positive Positive - colonies observed, total kill not achieved. This test demonstrated that the antimicrobial compositions A and B of the present invention were significantly more effective than the composition C disclosed in Garabedian et al. In particular, composition B, without ethylenediamine tetraacetic acid (EDTA) provides a more effective composition than A. Since Staphylococcus aureus is a commonly found organism on skin and is often difficult to kill completely, the formulation of the present invention as illustrated in Table II above, represents a marked and unexpected improvement over prior art cleansing formulations. Since surgical scrub products in use are diluted three-to-four times, it is important that a product must remain bactericidal under those conditions. It is clearly evident that the present invention as illustrated in Table II above effectively remains bactericidal at least up to a dilution of ten times its volume.

Claims: Claim for the following Contracting States : AT, BE, CH, DE, DK, FR, GB, IT, LI, NL, SE An antimicrobial composition comprising: (a) parachlorometaxylenol in an amount from 1.5 to 3.5 weight percent of the total composition; (b) polyoxypropylene-polyoxyethylene block copolymer in an amount from 1.0 to 6.0 weight percent of the total composition; (c) an ammonium salt of sulfated nonylphenoxypoly(ethyleneoxy) ethanol in an amount from 2.0 to 12.0 weight percent of the total composition; (d) ammonium lauryl sulfosuccinate in an amount from 2.0 to 12.0 weight percent of the total composition; (e) lanolin, a derivative of lanolin, aloe vera and/or isopropyl palmitate in an amount from 5.0 to 15.0 weight percent of the total composition; (f) hydroxypropyl methyl-cellulose or 2-hydroxyethyl-cellulose in an amount from 0.1 to 1.0 weight percent of the total composition; (g) an acid to adjust the pH in the range of from 4.0 to 6.0; and (h) the balance water. Claim for the following Contracting State : ES A process for preparing an antimicrobial composition comprising: (a) parachlorometaxylenol in an amount from 1.5 to 3.5 weight percent of the total composition; (b) polyoxypropylene-polyoxyethylene block copolymer in an amount from 1.0 to 6.0 weight percent of the total composition; (c) an ammonium salt of sulfated nonylphenoxypoly(ethyleneoxy) ethanol in an amount from 2.0 to 12.0 weight percent of the total composition; (d) ammonium lauryl sulfosuccinate in an amount from 2.0 to 12.0 weight percent of the total composition; (e) lanolin, a derivative of lanolin, aloe vera and/or isopropyl palmitate in an amount from 5.0 to 15.0 weight percent of the total composition; (f) hydroxypropyl methyl-cellulose or 2-hydroxyethyl-cellulose in an amount from 0.1 to 1.0 weight percent of the total composition; (g) an acid to adjust the pH in the range of from 4.0 to 6.0; and (h) the balance water, which process comprises adjusting the pH of an aqueous solution of components (a)-(f) with an acid to the range defined in (g).

Inventors: HOANG MINH Q, KHAN MOHAMMAD A, HOANG, MINH Q., KHAN, MOHAMMAD A.
Applicants: BECTON DICKINSON CO, BECTON, DICKINSON AND COMPANY
Application year: 1992
Main classification: C11D3
IPC codes: C11D1, A61L2, C11D3, A01N25, A01N31