Studies on the pharmacokinetics and mutagenic potential of rhodamine B

Rhodamine B is used as a marker dye in herbicide sprays. There is evidence that spray operators and others may absorb rhodamine B through the skin. This study was undertaken to investigate the in vivo mutagenicity of rhodamine B, to compare the in vitro mutagenicity of two commercial preparations of the dye with that of known mutagens including rhodamine 6G and to elucidate the pharmacokinetics of rhodamine B in the rabbit. Following the i.v. treatment of adult female New Zealand White rabbits with rhodamine B (1 mg/kg body wt), the plasma concentration of rhodamine B decreased rapidly and was accompanied by the appearance of at least four fluorescent polar metabolites. These metabolites, as well as a very small amount of rhodamine B, were also present in the urine which, when tested in the Ames assay was not significantly mutagenic against Salmonella typhimurium strains TA98 and TA100 either with or without metabolic activation. Urine from a human subject who had been contaminated with marker dye was also non-mutagenic. Both commercial preparations of rhodamine B were found to be weakly mutagenic, using the same assay system. It is concluded that while appropriate hygiene measures should be exercised by users of products containing this dye, the results do not support the hypothesis that rhodamine B is a genotoxic hazard in the mammalian organism.