Effect of licking about milk excretion of moxidectin administered pour-on in dairy cattle

IMPERIALE, F.; FARIAS, C.; SALLOVITZ, J.; LIFSCHITZ, A.; VIRKEL, G.; LANUSSE, C.

Tandil, Pcia. Bs. As.

Congreso; XL Reunión Anual de la Sociedad Argentina de Farmacología Experimental; 2008

Sociedad Argentina de Farmacología Experimental

Moxidectin (MXD) is a broad-spectrum endectocide antiparasitic drug extensively used in food-producing animals. Pour-on formulations of MXD are marketed internationally for use in dairy cattle. The current work was designed to measure plasma and milk concentration profiles of MXD using an HPLC-methodology after its pour-on administration to dairy cows. The influence of natural licking behavior of cattle on MXD plasma and milk concentrations was evaluated. Licking prevention during 5 days post-treatment determined changes on MXD plasma and milk kinetics. In licking-restricted cows, MXD plasma and milk availability were significantly lower than those in free licking animals. As shown earlier for other endectocide compounds, licking behavior may facilitate the oral ingestion of topically-administered drug in cattle. This would be consistent with the marked lower MXD concentration profiles measured in plasma and milk of licking prevented animals. The work reported here provides relevant information on the pattern of MXD excretion in milk after pour-on treatment, and contributes to understand the variability observed in the antiparasitic persistence of topically-administered endectocides in cattle. The implications of natural licking in topical treatments need to be seriously assessed to achieve accurate pharmacological studies aiming to a possible need of reviewing drug approval processes.