Absorption, metabolism, and excretion of thiabendazole in man and laboratory animals

Thiabendazole and its metabolic products were excreted rapidly by the kidney, and one-half of the radioactivity in the urine of man, less in the dog, and considerably more in the rat, was found to be associated with compounds which were identified chemically.

Abstract

After oral administration of 1.0 g of thiabendazole-14C to man, absorption was rapid and peak plasma concentrations of 13–18 μg/ml were found about 1 hour after treatment. Drug plasma levels declined rapidly and approached essentially zero between 24 and 48 hours. Thiabendazole and its metabolic products were excreted rapidly by the kidney, with 92% of the radioactivity found in the urine (87%) and feces (5%) within 48 hours. The bulk of this appeared in the urine in 24 hours. Thiabendazole was also rapidly absorbed from the gastrointestinal tract of rats and dogs. In these species, excretion was essentially complete within 3 days. Approximately one-half of the radioactivity in the urine of man, less in the dog, and considerably more in the rat, was found to be associated with compounds which were identified chemically. These compounds were primarily the glucuronide and sulfate esters of 5-hydroxythiabendazole. In plasma, and to a small extent in urine, both unchanged thiabendazole and free 5-hydroxythiabendazole were also found.