Ivermectin is an antiparasitic medicine (i.e. a medicine used to eliminate parasitic worms) for oral administration, and is approved in the US and some other countries in a tablet form. A new liquid formulation of ivermectin has been developed to facilitate dosing. This is a single dose, randomised, crossover study in healthy adult male and female volunteers, with doses taken after an overnight fast. Doses will be separated by washout period of at least 14 days. Twenty-one blood samples will be taken from each volunteer over 144 hours in each period. Concentrations of ivermectin in plasma will be measured using a validated chromatographic assay (LC-MS/MS). Standard pharmacokinetic parameters will be obtained and bioequivalence on the basis of rate and extent of drug absorption will be assessed.