The anthelmintic activity of some benzimidazole derivatives againstFasciola hepatica

Micronised mebendazole has been shown to have anthelmintic activity against Fasciola hepatica in rats and sheep. Activity is higher against non-egg-producing F. hepatica in bile ducts than against the migrating larval stages. Parbendazole, cambendazole and thiabendazole have been shown to be much less active, or devoid of activity, against mature and immature F. hepatica in rats, at elevated dose rates. Reasons for the differences, in terms of molecular structure, are briefly discussed and the pitfalls of structure/activity analyses are considered.