AN IVERMECTIN TABLET FOR SHEEP - EFFICACY AGAINST GASTROINTESTINAL NEMATODES AND A BIOAVAILABILITY COMPARISON WITH A LIQUID IVERMECTIN FORMULATION

An ivermectin tablet for oral administration to sheep was developed fo r use in countries where it is customary to treat sheep with anthelmin tic tablets. Tablets require no special administration equipment, and offer convenience for storage and transport. The ivermectin tablet, wh ich delivers 10 mg of ivermectin (200 mu g kg(-1) in a 50 kg sheep), h ad similar bioavailability to a liquid formulation of ivermectin (IVOM EC(R) Liquid for Sheep) as determined by peak plasma ivermectin concen trations and area under the concentration curve in plasma (P > 0.10). In dose confirmation trials in which nematode infections were induced in helminth-naive sheep, animals treated with the ivermectin tablet ha d significantly fewer adult and fourth-stage larval nematodes than unt reated control sheep (P < 0.01) with efficacies > 99% against all nema tode species tested. In six field trials evaluating the efficacy of th e ivermectin tablet in 240 Merino sheep, the reductions in faecal nema tode egg counts ranged between 98 and 100%, as determined by compariso n of pre- and post-treatment counts for the ivermectin-treated group.