The pharmacokinetics of orally administered ivermectin in african elephants (loxodonta africana): implications for parasite elimination

RAE GANDOLF, A.; LIFSCHITZ, A.; STADLER, C.; WATSON, B.; GALVANEK, L.; BALLENT, M.; LANUSSE, C.

JOURNAL OF ZOO AND WILDLIFE MEDICINE

Año: 2009 p. 107 - 112

1042-7260

Abstract: Loxodonta africana are susceptible to a wide variety of parasites that are often empirically treated with the broad spectrum antiparasitic ivermectin. The objectives of this study were to: Measure plasma ivermectin levels following administration of 0.1mg/kg ivermectin orally (p.o), compare plasma ivermectin levels following administration with regular versus restricted feed rations, and measure ivermectin excretion in feces. Using a cross-over design, six African elephants were divided into two groups. Ivermectin was administered and typical grain rations were either provided or withheld for 2 hr.  Blood and fecal samples were collected for 7 days following drug administration. After a 5-wk washout period, groups were switched and the procedure repeated. Plasma and fecal ivermectin was analyzed using HPLC. There was no difference in the pharmacokinetic data between the fed and fasted groups. Peak plasma concentration, area under the concentration vs time curve (AUC) and elimination half-life were between 5.41 and 8.49 ng/mL, 17.1 and 20.3 ng.d/mL and 3.12 and 4.47 d, respectively. On the other hand, high IVM concentrations were detected in faeces of elephants. The Cmax in faeces were between 264 and 311-fold higher than those obtained in plasma. The comparatively large AUC suggest that most of the drug is eliminated in the feces without systemic absorption.. Administration of 0.1 mg/kg ivermectin orally to elephants results in low plasma IVM levels when compared to other species. Based on these findings, administration of 0.2-0.4 mg/kg p.o. should be appropriate for eliminating many types of parasites in elephants and will minimize development of parasite resistance.      Key words:  Ivermectin, Loxodonta Africana, pharmacokinetics.