Pharmacokinetic and histopathological investigations of isometamidium in cattle

The absorption and distribution patterns of the trypanocidal drug isometamidium and its effect on tissues in cattle were characterised. After intramuscular administration of a prophylactic dose of 0.5 mg kg-1 bodyweight, the drug was rapidly detectable in serum at a mean maximum concentration of only 20 ng ml-1 and declined to concentrations of lower than 10 ng ml-1 within two hours. High drug concentrations were maintained at the injection site and in the liver and kidney for at least six weeks. At the injection site, tissue damage was severe and extensive, whereas in the liver and kidney no histopathological lesions were seen.