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

The pharmacokinetics and mammary excretion of moxidectin and eprinomectin were determined in water buffaloes (Bubalus bubalis) following topical administration of 0.5 mg kg1. Following administration of moxidectin, plasma and milk concentrations of moxidectin increased to reach maximal concentrations (Cmax) of 5.46 3.50 and 23.76 16.63 ng ml1 at Tmax 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 ml1) than in plasma (23.66 12.26 ng day ml1). 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 ofmoxidectin were probably due to a lower storage in fat associated with the fact that animalswere in lactation.Nevertheless, due to its high excretion inmilk and its high detectedmaximumconcentration inmilk which is equivalent or higher to the Maximal Residue Level value (MRL) (40 ng ml1), its use should be prohibited in lactating buffaloes. Concerning eprinomectin, the Cmax were of 2.74 0.89 and 3.40 1.68 ng ml1 at Tmax of 1.44 0.20 and 1.33 0.0.41 days in plasma and milk, respectively. The MRTand the AUC were similar for plasma (3.17 0.41 days and 11.43 4.01 ng day ml1) and milk (2.70 0.44 days and 8.49 3.33 ng day ml1). 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 ml1) supports the permitted use of eprinomectin in lactating water buffaloes.