Pharmacotherapeutic group: anthelmintics; benzimidazoles and related substances. ATC vet code: QP52ACO1.

Pharmacodynamic properties

Triclabendazole differs from other benzinidazoles in that it is a narrow spectrum anthelmintic. The drug accumulates significantly in both immature and adult stages of Fasciola hepatica and stimulates the major routes of the parasite's energy generating system, as demonstrated by glucose derived acetate and propionate formation. However under these conditions the parasite's motility decreased, indicating that the drug is not associated with inhibition of the energy generating pathways.
Triclabendazole inhibits colchicine binding to microtubular proteins suggesting interference of the drug with microtubular structure and function. The drug strongly inhibits the release of proteolytic enzymes in immature and adult parasites, a process dependent on microtubular functions. The precise molecular mode of this fasciolicidal drug remains to be elucidated.

Pharmacokinetic particulars

50-75% of the orally administered dose of triclabendazole is absorbed from the gastrointestinal tract. Very rapidly, absorbed triclabendazole is almost completely oxidised to its sulfoxide and sulfone. In cattle triclabendazole sulfoxide reaches peak concentrations 64-72 hours after administration of the product and the sulfone reaches peak concentrations 64-72 hours after administration. In sheep triclabendazole sulfoxide reaches peal concentrations approximately 20 hours after administration of the product and the sulfone reaches peak concentrations 30-32 hours after administration. Both metabolites bind strongly to plasma proteins, particularly albumin. Metabolities are excreted via the bile mainly as conjugates. More than 90-95% of the total dose of triclabendazole is excreted in the faeces, about 2% in the urine and less than 1% in the milk. The elimination is virtually complete by 10 days after administration.