Naloxone attenuates the anxiolytic action of diazepam in man.

The present study addresses the possible role of endorphins in mediating the anxiolytic properties of diazepam (DZM) in man. The ability of a low dose (0.4 mg. i.v.) of the specific opiate antagonist, Naloxone (NLX) to modify the anxiolytic action of DZM (0.07 mg/kg i.v.) in 22 patients anticipating minor orthopaedic surgery was evaluated. The study was performed in a double-blind placebo (saline)-controlled, randomized design. DZM administered 3 hours pre operation, reduced the anxiety experienced by subjects as estimated on a formal rating scale completed by the patients. NLX, as compared to saline, given 30 min post DZM significantly and strongly attenuated, but did not abolish this effect of DZM. These findings parallel observations in rats of the ability of NLX to block the action of DZM in the conflict test and suggest that the anxiolytic action of DZM in man may be partially mediated by endorphins.