Combined administration of abamectin and albendazole as a controlled-release capsule in lambs: pharmaco-therapeutic evaluation.

CASTELLS, D.; SUAREZ, G.; ALVAREZ, L.; FAGIOLINO, P.; LANUSSE, C.

Buenos Aires

Conferencia; 23 International Conference of the World Association for the Advancement of Veterinary Parasitology; 2011

AAVP

In an attempt to overcome the inconvenient of the development of resistance to the available anthelmintic chemical groups, pharmaceutical formulations combining benzimidazole and macrocyclic lactone compounds are available in the veterinary pharmaceutical market. The goal of the current work was to evaluate the anthelmintic efficacy and the pharmacokinetic profiles of both abamectin (ABM) and albendazole (ABZ) after their oral administration as a combined controlled-release capsule in lambs. Twenty (20) Corriedale lambs naturally infected with multiple anthelmintic resistant gastrointestinal nematodes, were randomly allocated into two experimental groups (n=10): an untreated control and a group treated with the ABM+ABZ controlled-release capsule (Bionic®, Ancare, New Zealand) by the oral route. Faecal and plasma samples were collected over 100 days post-treatment. ABM and ABZ sulphoxide (ABZSO) plasma concentrations were measured by HPLC. The efficacy of the treatment, estimated at different days post-treatment, was assessed by the faecal egg count reduction test (FECRT). Additionally, faecal samples were cultured to determine nematode genus and species. Both ABM and the ABZSO metabolite were measured in the bloodstream up to 92 days post treatment. The ABM peak plasma concentration (Cmax) was16.5 ± 7.7 ng/mL reached at 8 days post-treatment. The ABM area under the concentration vs. time curve (AUC0-t) was 840 ± 377 ng.day/mL. While ABZ parent drug was not detected at any time post-treatment, its active ABZSO metabolite, reached a Cmax value of 0.2 ± 0.1 µg/mL and AUC0-t of 8.6 ± 3.4 μg.day/mL. Plasma concentrations of both ABM and ABZSO increased gradually to achieve the steady-state (10.3 ng/mL and 0.1 μg/mL, respectively) at approximately 8 days, which was maintained over 77 days post-treatment. The FECRT estimated at 13 days post-treatment was 73%. However, between days 29 to 92 post-treatment, an enhanced egg output reduction (87-98%) was observed The faecal cultures showed Haemonchus spp. as the main nematode surviving the combined ABM+ABZ treatment. The sustained presence of the combined molecules delivered by the capsule for a long period, may have accounted for the observed efficacy against multiple resistant nematodes.