Diazepam reduces stress-induced analgesia in humans

The analgesic effects of a repetitive stress induced by anticipation of pain (noxious footshock) were studied on both the threshold of a nociceptive flexion reflex and the corresponding pain sensation after a 4-day-treatment of diazepam vs placebo (cross-over and double-blind study) in normal volunteers. During diazepam, the stressor stimulus produced a weaker depression on both nociceptive reflex and pain sensation than that observed during placebo. Furthermore, the reversal effect by naloxone was much more marked during placebo than during diazepam. These data clearly suggest a possible moderating action of benzodiazepine brain type receptors upon the endogenous opiate systems involved in the phenomenon of stress-induced analgesia in humans.