Activity and safety of Bronopol 23 Bronopol is most stable under acid conditions, although it demonstrates high anti- bacterial activity over a wide pH range. The mode of decomposition has been studied in detail, and a number of the decomposition products identified. The assay methods described are capable of estimating Bronopol in many formulations at its normally used levels, the sensitivity of the methods is dependent upon the nature of the formulations in certain cases levels as low as 5 ppm can be assayed. Bronopol is generally used as a preservative in formulations at levels between 0.01 and 0.1 •o. Animal toxicity studies and human patch tests have demonstrated the safety of Bronopol when used at these concentrations. In particular, no evidence of human skin sensitisation has been obtained at these levels. Bronopol has been shown to be an effective antibacterial agent in a range of formula- tions including shampoos, skin creams and sprays and bath products. Many of the ingredients used in such products have been shown to have little or no effect on the antibacterial activity of Bronopol, although compounds containing sulphydryl groups are antagonistic to its activity. ACKNOWLEDGMENTS The authors wish to acknowledge the assistance of the following staff of The Boots Company Limited in the production of the data included: Dr D. F. Spooner (micro- biology) Mr E. L. Crampton (chemistry) Mr D. A. Elvidge, the late Mr C. Vickers, and Mr J. S Wragg (analysis) Dr P. C. Risdall and Miss M. M. Sutton (toxicology) and Mr K. G. Jackson and Dr D. P. Stokes (formulation). In addition, the authors wish to thank Dr C. D. Calnan, Institute of Dermatology, University of London and Professor H. I. Maibach, Department of Dermatology, University of California for their help in the completion of the human skin studies. REFERENCES 1 Hodge, E. B., Dawkins, J. R. and Kropp, E. A new series of antifungal compounds. J. Am. Pharrn. Ass., Sci. Ed. 43 501 (1954). 2 Zsolnai, T, Versuche zur Entdecktmg neuer Fungistatika. II. Nitro-verbindungen. Blochem. Pharmac. s 287 (1961). 3 Croshaw, Betty, Groves, M. J. and Lessel, B. Some properties of Bronopol, a new antimicrobial agent active against Pseudomonas aeruginosa. J. Pharrn. Pharmac. 16 Suppl., 127T (1964). 4 Clark, N. G., Croshaw, Betty, Legetter, B. E. and Spooner, D. F. Synthesis and antimicrobial activity of aliphatic nitro compounds. J. Med. Chem. 17 977 (1974). 5 Morse, L. J. and Schonbeck, L. E. Hand lotions, a potential nosocomial hazard. New. Engl. J. Med. 278 376 (1968). 6 Sykes G. and Smart, R. Preservation of preparations for application to the skin. Am. Perfurn. Cosmet. 84 45 (1969). 7 Smart, R. and Spooner, D. F. Microbiological spoilage in pharmaceuticals and cosmetics. J. $oc. Cosmet. Chem. 23 721 (1972). 8 Malcolm, S. A. and Woodroffe, R. C. S. The relationship between water-borne bacteria and shampoo spoilage. J. Soc. Cosmet. Chem. 26 277 (1975). 9 Tenenbaum, S. The significance of pseudomonads in cosmetic products. Am. Perfum. Cosmet. 86 47 (1971). 10 Thomas, M. J. and Majors, P. A. Animal and human microbiological safety testing of cosmetic products. J. Soc. Cosmet Chem. 24 135 (1973). 11 Marples, R. R. and Kligman, A.M. Methods for evaluating topical antibacterial agents on human skin. Antimicrob. Agents Chernother. $ 323 (1974).

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