Comparative pharmacokinetic and pharmacodynamic response of single and double intraruminal doses of ivermectin and moxidectin in nematode-infected lambs.

LLOBERAS, M.; ALVAREZ, L.; ENTROCASSO, C.; BALLENT, M.; VIRKEL, G.; LUQUE, S.; LANUSSE, C.; LIFSCHITZ, A.

NEW ZEALAND VETERINARY JOURNAL

NEW ZEALAND VETERINARY ASSOC INC

Año: 2015

0048-0169

AIMS:To compare the pharmacokinetics, distribution and efficacy (pharmacodynamic response) of intraruminal ivermectin (IVM) and moxidectin (MXD) administered at 0.2 and 0.4 mg/kg to naturally nematode-infected lambs, and to determine the ex vivo accumulation of these anthelmintics by Haemonchus contortus.METHODS:Romney Marsh lambs, naturally infected with IVM-resistant H. contortus, were allocated to treatment groups based on faecal nematode egg counts. They received 0.2 or 0.4 mg/kg IVM or MXD (n=10 per group), or no treatment (Control; n=6), on Day 0. Samples from four animals from each treatment group, including abomasal parasites, were obtained on Day 1. Plasma samples were also collected from Day 0 to 14, and a faecal egg count reduction test (FECRT) and a controlled efficacy trial were carried out on Day 14. Concentrations of IVM and MXD in plasma, in abomasal and intestinal tissues and in H. contortus were evaluated by high-performance liquid chromatography. Additionally, the ex vivo drug accumulation of IVM and MXD by H. contortus was determined.RESULTS:Peak plasma concentrations and the area under the concentration vs. time curve for both IVM and MXD were higher for 0.4 than 0.2 mg/kg treatments (p