The morphine sparing effect of physostigmine

The antinociceptive effect of morphine was studied in tail-flick- and aceti c acid-induced writhing in mice. Morphine effect was dose-related (1, 2 and 5 mg/kg s.c.). Physostigmine (0.05 and 0.1 mg/kg i.p.) potentiated the ant inociceptive effect of morphine, and the anticholinergic, scopolamine (1 mg /kg i.p.), reversed the potentiating effect of physostigmine, indicating th e involvement of the cholinergic system in pain. Coadministration of physos tigmine would increase the therapeutic index of morphine thereby sparing th e dose of morphine and also possibly the side effects including the develop ment of tolerance and addiction. (C) 1999 Prous Science. All rights reserve d.