Pyrvinium pamoate, tablets and suspension, was administered as single 350-mg doses to 12 healthy male volunteers to determine whether there had been any systemic absorption. Six subjects received tablets and 6 received suspension on the first day; on day 8, subjects received the other dose form. Up to 4 days after administration there was no evidence of drug in blood and urine by spectroflorometric assay. Metabolic studies in rats showed minute quantities of drug in the liver and plasma but not of any metabolites.