Author(s): McClain DA, Hug CC Jr, McClain DA, Hug CC Jr
Abstract Share this page
Abstract Fentanyl is considered to be a short-acting narcotic analgesic but prolonged and recurrent ventilatory depression has been reported. We examined fentanyl kinetics and excretion in 7 healthy male subjects who were given a 3.2- or 6.4-micrograms/kg dose of 3H-fentanyl intravenously. Arterial blood and urine samples were analyzed for unchanged fentanyl and total radioactivity. Fentanyl concentrations fell rapidly and 98.6\% of the dose was eliminated from plasma in 60 min but the terminal elimination phase of fentanyl from the body was slow (t1/2 beta = 219 min) due to the slow return of the unchanged drug from a peripheral compartment to the central compartment where elimination occurred primarily by biotransformation. Eighty-five percent of the dose was recovered in urine and feces in 72 hr; less than 8\% was recovered as unchanged fentanyl. There were fluctuations in plasma fentanyl levels during the elimination phase in all cases. The long t1/2 beta and fluctuations in plasma levels may contribute to prolonged and recurrent ventilatory effects of fentanyl.
This article was published in Clin Pharmacol Ther
and referenced in Journal of Forensic Research