Factors affecting pharmacokinetics of benzimidazole anthelmintics in food-producing animals: The consequences and potential risks

Benzimidazoles are frequently and widely used veterinary anthelmintics. Unfortunately, an administration of these anthelmintics does not always result in the expected therapeutic success. Many host-related factors modify pharmacokinetic behavior and efficacy of a chosen anthelmintic. Pharmacokinetics of anthelmintics varies among animals of different species, sex and age. Also diseases, medication, feed and environmental conditions can significantly affect behavior of anthelmintics and resultant drug efficacy in animals. The presented review gathers information, gained in last 20 years, on factors which bring about the variability in performance of benzimidazole anthelmintics in food-producing animals. It is focused particularly on differences in absorption and metabolism of these anthelmintics as these stages of the pharmacokinetic process seem to be the most important for the overall anthelmintic efficacy. The consequences of abnormalities and alterations in pharmacokinetics of benzimidazole anthelmintics are summarized and discussed.