The Pharmacokinetics of Heroin in Patients with Chronic Pain

Abstract

We measured blood concentrations of heroin and its active metabolites, 6-acetylmorphine and morphine, serially in 11 patients with chronic pain (9 of whom had cancer) after intravenous injection, intravenous infusion, intramuscular injection, and an oral dose of heroin hydrochloride. Parenteral heroin provided measurable blood levels of heroin, 6-acetylmorphine, and morphine. Blood levels of heroin and 6-acetylmorphine reached their maximal concentrations within minutes and were cleared rapidly. The mean half-life of heroin (±S.D.) after intravenous injection or infusion was only 3.0±1.3 minutes, and the mean clearance of heroin from the blood at apparent steady state was 30.8±2.1 ml per kilogram of body weight per minute. Morphine levels rose more gradually, and morphine was cleared much more slowly.