The Analgesic Effect of the Combined Treatment of Aspirin with Different Antidepressants on Thermally and Chemically Induced Pain in Albino Mice

Abdalla Salem Elhwuegi, Kalthom Mahmoud Hassan. Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Al-fateh University of Medical Sciences, Tripoli, Libya.

Objectives: Combination analgesics can provide more effective pain relief for a broader spectrum of pain. This research examines the possible potential analgesic effect of the combined treatment with aspirin and different classes of antidepressants drugs in two different models of pain using Albino mice.

Methods: Different groups of six animals each were injected intraperitoneally by different doses of aspirin (50, 100, or 200 mg/kg), imipramine (2.5, 7.5, 15 or 30 mg/kg), fluoxetine (1.25, 2.5, 5 or 7.5 mg/kg), mirtazapine (1.25, 2.5, or 5 mg/kg) and a combination of a fixed dose of aspirin (100 mg/kg) with the different doses of the three antidepressant drugs. One hour later the analgesic effect of these treatments were evaluated against thermally (hotplate) and chemically (acetic acid) induced pain. All data were subjected to statistical analysis using un-paired t-Test.

Results: Aspirin produced dose dependent analgesic effect only against chemically induced pain. The three selected antidepressants produced dose dependent analgesia against both types of pain. The addition of a fixed dose of aspirin to imipramine significantly increased the reaction time (RT) of the lowest dose (by 23%) and the highest dose (by 20%) in the hotplate method; while this potentiation was statistically significant with all doses of imipramine against chemical pain (writhing was inhibited by 11%, 9%, 8% and 20% respectively). The addition of the fixed dose of aspirin to fluoxetine significantly increased RT by 13% of the dose 2.5 mg/Kg in the hotplate method; while this potentiation was statistically significant with 5 mg/kg and 7.5 mg/kg of fluoxetine against chemical pain (writhing was inhibited by 20% and 19% respectively). Finally, the addition of the fixed dose of aspirin significantly potentiated the antinociceptive effect of the different doses of mirtazapine using both pain models (RT was increased by 24%, 54% and 38% respectively in the hotplate method; and writhing was inhibited by 19%, 29% and 23% respectively in the chemical pain).

Discussion: The differing parallel central and peripheral mechanisms of action of these drugs might have been the cause of the improved analgesia.

Conclusion: The combination of aspirin with an antidepressant might produce better analgesia. This type of combination can increase the efficacy of pain management and reduce side effects by using smaller doses of each drug.