Inhibition of morphine analgesia by ascorbate.

Oral administration of single doses of ascorbate produced a decrease in the analgesic effect of morphine in mice when assayed by the tail-flick test. Inhibition of analgesia was dose dependent, had a rapid onset (2 hr) and long duration (48 hr). Ascorbate doses over 8 mg/kg also protected mice from lethal doses of morphine. These findings are in accord with recent reports that ascorbate destroys opioid receptor in vitro and indicates that a similar effect occurs in vivo.