Naloxone displacement at opioid receptor sites measured in vivo in the human brain

We report the use of a sensitive non-tomographic positron detecting system to measure the dose-response curve of naloxone in human brain. [C-11]Diprenorphine was administered to normal volunteers in tracer amounts and, 30 min later, various bolus doses of naloxone were given (1.5-160 mug/kg) intravenously and change in [C-11]diprenorphine binding monitored over the next 30 min. We found that this method produced results consistent with existing data. It was observed that similar to13mug/kg of naloxone (similar to1 mg in an 80 kg man) was required to produce an estimated 50% receptor occupation. This is consistent with the clinical dose of naloxone used to reverse opiate overdose (0.4 mg - 1.2 mg). (C) 2002 Elsevier Science B.V. All rights reserved.