Pharmacokinetics of levamisole.

Levamisole is rapidly absorbed following oral, intramuscular, or subcutaneous administration to several animal species. Extensive metabolism occurs with rapid excretion of drug and metabolites, equally distributed between urine and feces in rats. In man a single oral dose of 150 mg produces a peak levamisole plasma level of 0.5 microgram/ml after 2-4 hours. Unchanged drug represented only one third of total plasma radioactivity. Urinary and fecal excretion of radioactivity amounted to 60% and 4% respectively after 24 hours, with only small amounts of unchanged drug being excreted. Levamisole syrup and tablets were bio-equivalent.