Effects of 1,1'-hexamethylene-bis-[(5-p-chlorophenyl)-biguanide] on the genome and on the synthesis of nucleic acids and proteins in the bacterial cells

Final Report on the Safety Assessment of Chlorhexidine/Chlorhexidine Diacetate/Chlorhexidine Dihydrochloride/Chlorhexidine Digluconate

Chlorhexidine and its Diacetate and Digluconate salts are used in cosmetics as preservatives. Chlorhexidine Digluconate was slightly toxic in oral and inhalation studies. At cosmetic use concentrations, Chlorhexidine Digluconate was not irritating to the eyes or skin. Positive sensitization reactions were cited in provocative patch testing at 1.0% concentration in patients with eczema, but not in predictive patch testing of 0.05% in normal subjects. In bacterial assays, Chlorhexidine tested both positive and negative for mutagenesis. In two mammalian systems, Chlorhexidine Digluconate was not genotoxic. p-Chloroaniline is a degradation product of Chlorhexidine salts. A study of the degradation of Chlorhexidine revealed minor amounts of p-chloroaniline after 36 weeks storage. Chlorhexidine Digluconate was not carcinogenic in a 2-year drinking water study. On the basis of the data presented in this report, it is concluded that Chlorhexidine and its salts are safe for use in cosmetic products at concentrations up to 0.14% calculated as Chlorhexidine free base; 0.19% as Chlorhexidine Diacetate; 0.20% as Chlorhexidine Digluconate; and 0.16% as Chlorhexidine Dihydrochloride.

The reaction of the mutagen 1,1'-hexamethylene-bis-[(5-p-chlorophenyl)-biguanide] with guanosine and cysteine

The mutagen 1,1'-hexamethylene-bis[(5-p-chlorophenyl)-biguanide] reacts at 37 degrees C with guanosine and guanine to yield xanthosine or xanthine and oxidizes cysteine to cystine. After treatment of a guanosine-labelled DNA sample from Escherichia coli with the mutagen xanthine could be detected as a reaction product. At a slow rate the mutagen is hydrolysed spontaneously yielding urea, 1.6-hexanediol and 4-chloroaniline. The reaction mechanisms both of the hydrolysis and of the reaction with cysteine and guanosine are discussed.