A comparative kinetic study of ivermectin and moxidectin in lactating camels (Camelus dromedarius)

The plasma and milk kinetics of ivermectin (IVM) and moxidectin (MXD) was e valuated in lactating camels treated subcutaneously (0.2 mg kg(-1))with com mercially available formulations for cattle. Blood and milk samples were ta ken concurrently at predetermined times from 12 h up to 60 days post-admini stration. No differences were observed between plasma and milk kinetics of IVM, while substantial differences were noted between plasma and milk profi les of MXD in that both the maximal concentration (C-max) and the area unde r concentrations curves (AUC) were three to four-fold higher for milk than for plasma. The time (T-max) to reach C-max was significantly faster for MX D (1.0 day) than that for IVM (12.33 days). The C-max and the AUC were sign ificantly higher for MXD (C-max = 8.33 ng ml(-1); AUC = 70.63 ng day ml(-1) ) than for IVM (C-max = 1.79 ng ml(-1); AUC = 30.12 ng day ml(-1)) respecti vely. Drug appearance in milk was also more rapid for MXD (T-max = 3.66 day s) compared to IVM (T-max = 17.33 days). The extent of drug exchange from b lood to milk, expressed by the AUC(milk)/AUC(plasma) ratio, was more than t hree-fold greater for MXD (4.10) compared to that of TVM (1.26), which is c onsistent with the more lipophilic characteristic of MXD. However, the mean residence time (MRT) was similar in both plasma and milk for each drug. (C ) 1999 Elsevier Science B.V. All rights reserved.