The study on the biological fate of paraben at the dose of practical usage in rat. III. The effects of salicylic acid on the fate of ethyl paraben.

The biological fates of ethyl paraben were investigated after the simultaneous administration with salicylic acid. Those fates were compared with those of ethyl paraben alone obtained in the previous experiments. The biological fates of ethyl paraben after the simultaneous administration with salicylic acid were different from those of ethyl paraben alone as reported in the previous reports. The excretion of unconjugated p-hydroxybenzoic acid, which is a hydrolyzed product of ethyl paraben, increased and those of p-hydroxyhippuric acid, glycine conjugate of p-hydroxybenzoic acid, and p-hydroxybenzoyl glucuronide, its ester type glucuronide, decreased. The blood concentration patterns were considerably different from those of ethyl paraben alone, especially the elimination of every metabolite was delayed. Pharmacokinetic analyses on the data of blood concentration were carried out and the results also show the interaction of salicylic acid on the biological fate of ethyl paraben.