THE UPTAKE OF FENBENDAZOLE BY CATTLE AND BUFFALO FOLLOWING LONG-TERM LOW-LEVEL ADMINISTRATION IN UREA MOLASSES BLOCKS

Fenbendazole (Panacur bolus, Hoechst India Ltd) was incorporated at a rate of 0.5 g/kg into urea-molasses blocks made by two different proce sses. The concentration of the drug in blocks and its bioavailability were measured using plasma oxfendazole as marker. The recovery of the drug in blocks made by a warm process was 68% and the plasma oxfendazo le concentration remained fairly stable at 0.2 and 0.12 mug/ml from da y 6 of feeding in cattle and buffalo, respectively. The drug seemed to be inactivated in blocks made by a hot process, with reduced bioavail ability. A low and sustained plasma concentration of the active metabo lite of the drug could be maintained by self-medication using urea-mol asses blocks as fenbendazole carrier.