Plasma and milk kinetic of eprinomectin and moxidectin in lactating water buffaloes (Bubalus bubalis)

Abstract The pharmacokinetics and mammary excretion of moxidectin and eprinomectin were determined in water buffaloes ( Bubalus bubalis ) following topical administration of 0.5 mg kg −1 . Following administration of moxidectin, plasma and milk concentrations of moxidectin increased to reach maximal concentrations ( C max ) of 5.46 ± 3.50 and 23.76 ± 16.63 ng ml −1 at T max of 1.20 ± 0.33 and 1.87 ± 0.77 days in plasma and milk, respectively. The mean residence time (MRT) were similar for plasma and milk (5.27 ± 0.45 and 5.87 ± 0.80 days, respectively). The AUC value was 5-fold higher in milk (109.68 ± 65.01 ng day ml −1 ) than in plasma (23.66 ± 12.26 ng day ml −1 ). The ratio of AUC milk/plasma for moxidectin was 5.04 ± 2.13. The moxidectin systemic availability (expressed as plasma AUC values) obtained in buffaloes was in the same range than those reported in cattle. The faster absorption and elimination processes of moxidectin were probably due to a lower storage in fat associated with the fact that animals were in lactation. Nevertheless, due to its high excretion in milk and its high detected maximum concentration in milk which is equivalent or higher to the Maximal Residue Level value (MRL) (40 ng ml −1 ), its use should be prohibited in lactating buffaloes. Concerning eprinomectin, the C max were of 2.74 ± 0.89 and 3.40 ± 1.68 ng ml −1 at T max of 1.44 ± 0.20 and 1.33 ± 0.0.41 days in plasma and milk, respectively. The MRT and the AUC were similar for plasma (3.17 ± 0.41 days and 11.43 ± 4.01 ng day ml −1 ) and milk (2.70 ± 0.44 days and 8.49 ± 3.33 ng day ml −1 ). The ratio of AUC milk/plasma for eprinomectin was 0.76 ± 0.16. The AUC value is 20 times lower than that reported in dairy cattle. The very low extent of mammary excretion and the milk levels reported lower than the MRL (20 ng ml −1 ) supports the permitted use of eprinomectin in lactating water buffaloes.