Naloxone-ethanol interaction in experimental and clinical situations

The effect of naloxone on ethanol-induced impairment of psychomotor performance was studied in a series of three placebo-controlled, double-blind trials. In all trials, two successive intravenous injections of naloxone (0.4 and 2.0 mg) were given at an interval of 0.5-1.5 hours. Cross-over trials with healthy volunteers (n = 17) were performed in laboratory. In these conditions, naloxone alone had no effect on performance. Ethanol alone (1.0 and 1.5 g/kg) dose-dependently induced nystagmus and impaired coordination, reactions, hand cooperation, body balance, flicker discrimination and extraocular muscle balance. When naloxone was given after ethanol, the first injection reduced slightly but significantly ethanol-induced (1.5 g/kg) nystagmus, while the second injection did not enhance this counteraction any more. Other alcohol effects were not significantly antagonized by naloxone. The clinical part of the study, consisting of parallel groups of either naloxone (n = 11) or saline (n = 7) -treated alcohol-intoxicated (mean blood alcohol concentration 2.9 mg/ml) out-patients, most of them alcoholics, showed that no counteraction of alcohol inebriation (measured by clinical inebriation tests) was associated with the treatment with naloxone in the clinical situation either. Our results suggest that naloxone has no clinical significance in antagonizing ethanol intoxication. The inebriating effects of ethanol are not importantly mediated via central opioid mechanisms.