The fate of praziquantel in the organism III. Metabolism in rat, beagle dog and rhesus monkey

Summary

The radioactive constituents of specimens of serum, urine and faeces of wistar rats, beagle dogs and rhesus monkeys following peroral and intravenous administration of praziquantel-¹⁴C were analyzed by radio thin layer chromatographic techniques. Corresponding investigations were done with specimens of bile and liver tissue of wistar rat. These investigations yielded the following results:

Praziquantel is quantitatively and rapidly absorbed and metabolized by all species. No unmetabolized drug was found in any of the excretion products. The excretion occurs as a variety of metabolites, some of them representing conjugates with glucuronic and/or sulfuric acid.

The serum metabolite patterns of praziquantel following p. o. administration are characterized by a strong “first pass effect: after p. o. administration only a small proportion of unchanged drug reaches the general blood circulation. In contrast to this substantial amounts of praziquantel are present in the serum over a longer time period after i. v. administration.

These differences are due to intensive metabolisation by the liver, being particularly prominent in wistar rats and rhesus monkeys, and somewhat less in beagle dogs.