Oral pharmacokinetics of fenbendazole in llamas, South American Camelids

Llamas, South American Camelids are increasingly popular in the United States, as a source of fiber, livestock guard, and pack animals. Gastrointestinal parasites have been identified as a major health problem in all classes of livestock including llamas. Currently, there are no approved anthelmintics available for use in llamas. In this study, the pharmacokinetics of a single, oral administration of fenbendazole paste at a minimum target dose of 5mg/kg, with an upper limit of <10mg/kg, was evaluated in llamas. Plasma fenbendazole concentration time profiles were best described by a single compartment model. After oral administration of fenbendazole, T(max) and Cp(max) were 28.39+/-12.80h, and 0.28+/-0.17µg/ml, respectively. The T(1/2alpha) and T(1/2beta) were 16.25+/-11.67 and 36.00+/-25.00h, respectively. The apparent volume of distribution (V(d)) and the area under the curve (AUC) were 11.28+/-4.66l/kg, and 22.52+/-8.67µgh/ml, respectively. The results of this preliminary study indicate that when the paste formulation of fenbendazole is administered orally to llamas, its rate of absorption appears to be very similar to that of other ruminants including sheep, goats, and cattle as indicated by the time required to reach peak plasma concentrations. It was also found that the rate of elimination of fenbendazole was prolonged in llamas as compared to sheep, goats, and cattle.