THE PHARMACOKINETICS OF MOXIDECTIN AFTER ORAL AND SUBCUTANEOUS ADMINISTRATION TO SHEEP

The pharmacokinetic parameters of moxidectin were determined in ten sh eep following a single subcutaneous or oral drench at a dose of 0.2 mg .kg(-1). The plasma kinetics were best fitted by a two-compartment mod el. Moxidectin was detected in the plasma at the first sampling time ( 1 h) and thereafter for at least 60 d. The AUC were similar after both treatments indicating the same bioavailability for the two routes of administration. The oral route was characterized by a higher Cmax valu e (28.07 ng.mL(-1)) than after subcutaneous injection (8.29 ng.mL(-1)) and by significantly faster absorption as indicated by Tmax of 0.22 d and 0.88 d for oral and subcutaneous administrations, respectively. T he most striking result of this experiment was the longer mean residen ce time reported for the subcutaneous route, i.e. 16.80 d as compared to 12.55 d for the oral drench. This difference is in agreement with p revious studies demonstrating the longer anthelmintic efficacy of the subcutaneous route in comparison with oral administration. (C) Inra/El sevier, Paris.