Biotransformation of chlormezanone, 2-(4-chlorophenyl)-3-methyl-4-metathiazanone-1,1-dioxide, a muscle-relaxing and tranquillizing agent: the effect of combination with aspirin on its metabolic fate in rats and mice.

1. After oral administration of [14C]chlormezanone, about 74% of the dose was excreted into the urine of rats within 24 h and 21% into urine of mice within 2 h. 2. Biliary excretion of radioactivity was about 10% of the dose in rats. 3. Six metabolites in the urine of rats and mice were identified as p-chlorobenzoic acid, p-chlorohippuric acid, N-methyl-p-chlorobenzamide, 2-[N-methyl-N-(p-chlorobenzoyl)]carbamoylethylsulphonic acid, 3-sulphopropionic acid and the glucuronide of p-chlorobenzoid acid. 4. The effect of combination with aspirin on the metabolic fate of chlormezanone was investigated in rats and mice. Aspirin had no effect on the metabolite pattern in either species but reduced the rate of excretion, particularly in the mouse.