Study of anti-nociceptive potential of physostigmine and its combination with morphine in albino rats

Background: The cholinergic drugs are having antinociceptive potential but are under investigation because of their serious side effects. It is difficult to accept them as an analgesic. This study is undertaken in the experimental animal models for the evaluation of the antinociceptive potential of Physostigmine and its combination with Morphine at their sub-analgesic doses. The objective of the study was to evaluate the antinociceptive effect of Physostigmine and its combination with subanalgesic dose of morphine and comparing their effect with analgesic dose of Morphine.Methods: Antinociceptive effect of Physostigmine in three graded doses (50, 100 & 200 µg/kg) and combination of Physostigmine at low dose (50 µg/kg) with sub-analgesic dose of Morphine (0.1 mg/kg) and Morphine in analgesic dose (1 mg/kg) was evaluated by using tail flick method in albino rats.Results: Comparison of maximal possible effect in percentage (MPE in %) between groups at 90 minutes in control, Morphine, Physostigmine in 50, 100, 200 µg/ kg doses and combination group respectively, demonstrated significant difference (p < 0.001) when compared by one way ANOVA test. There was no much increase in the tail flick latency in Physostigmine 50 µg/kg (SC) treatment at 90 min (3.08±0.15) in comparison to control (NS) treatment group. Combination treatment of low doses of both Physostigmine 50 µg/kg + Morphine 0.1 mg/kg increased the tail flick latency 90 min (7.08±0.15) in-comparison to control (NS) treatment group (3.33±0.11).Conclusions: Physostigmine is more potent antinociceptive than Morphine and Physostigmine potentiated the antinociceptive activity of low dose of standard drug Morphine