AbstractHealthy male volunteers participated in two studies of the pharmacokinetics of ciramadol, an investigational analgesic. For the dose‐proportionality study, subjects received single i.v. doses of 15, 30, or 60 mg of ciramadol on three separate occasions. Serum samples and urine were collected 48 hr after each dose. Overall mean kinetic values for ciramadol were: volume of distribution, 1.5 liters/kg; elimination half‐life, 3.7 hr; total clearance, 4.9 ml/min/kg. Clearance did not change systematically with dose. Mean 48‐hr urinary excretion was 40% of the dose as the intact drug, with another 24% excreted as ciramadol conjugates; these were dose‐independent. For the bioavailability study, subjects received a 30‐mg dose of ciramadol i.v., i.m., or orally on three separate occasions. The mean absolute systemic availability of the i.m. dose was 98%; the absolute availability of the oral dose was 82%. Peak serum concentration of 235 and 155 ng/ml were attained at 0.27 and 1.5 hr after the i.m. and oral doses, res