Comparative pharmacokinetic and efficacy assessments of single and double ivermectin and moxidectin doses 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 count s. 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