The analgesic effect of different antidepressants combined with aspirin on thermally induced pain in Albino mice.

Background: Combination analgesics provide more effective pain relief for a broader spectrum of pain. This research examines the possible potentiation of the analgesic effect of different classes of antidepressants when combined with aspirin in thermal model 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 antidepressants. One hour later the analgesic effect of these treatments were evaluated against thermally induced pain. All data were subjected to statistical analysis using unpaired Student's t-test.

Results: Aspirin had no analgesic effect in thermally induced pain. The three selected antidepressants produced dose dependent analgesia. 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%). The addition of the fixed dose of aspirin to fluoxetine significantly increased RT by 13% of the dose 2.5 mg/kg. Finally, the addition of the fixed dose of aspirin significantly potentiated the antinociceptive effect of the different doses of mirtazapine (RT was increased by 24, 54 and 38% respectively).

Conclusion: Combination of aspirin with an antidepressant might produce better analgesia, increasing the efficacy of pain management and reduces side effects by using smaller doses of each drug.