Research Article Antinociceptive potential of Pilocarpine and its combination with Morphine in

Objectives: To evaluate the antinociceptive effect of Pilocarpine and its combination with sub-analgesic dose of morphine and comparing their effect with analgesic dose of Morphine. Materials and Methods: Antinociceptive effect of Pilocarpine in three graded doses (1, 5, 10mg/kg) and combination of Pilocarpine at low dose (1mg/kg) with sub-analgesic dose of Morphine (0.1mg/kg) and Morphine in analgesic dose (1mg/kg) was evaluated by using Tail Flick Method and Tail Immersion Method in Albino Rats. Results: Comparison of maximal possible effect in percentage (MPE in %) between groups at 90 minutes in control, Morphine, Pilocarpine in 1, 5, 10mg / kg doses and combination group respectively, demonstrated significant difference (p < 0.001) when compared by one way ANOVA where as Post hoc comparison test showed increased MPE at 90 min in comparison to control. There was no significant increase in MPE by Pilocarpine 1mg/kg (p>0.05) when compared to control. Morphine 1mg/kg and Pilocarpine 10mg/kg did not show any significant difference in between groups (p>0.05). Conclusion: Pilocarpine in the doses of 5mg/kg and 10mg/kg demonstrated significant antinociceptive activity in comparison to control. Morphine 1mg/kg dose showed more antinociceptive activity when compared to Pilocarpine 1mg/kg and 5mg/kg and is equipotent to Pilocarpine 10mg/kg. Combination of low doses of either Pilocarpine (1mg/kg) potentiated antinociceptive effect of low dose of Morphine (0.1mg/kg) indicating that cholinergic drugs like Pilocarpine can be combined with Morphine for enhancement of Morphine action