Research Paper - Analgesic activity of venlafaxine and its interactions with tramadol, celecoxib and amlodipine in mice

Objective: To study the analgesic activity of venlafaxine and its interactions with tramadol, celecoxib and amlodipine. Materials and Methods: Antinociceptive action of venlafaxine (5, 7.5, 10 and 22.5 mg/kg) was studied in mice (tail flick and writhing tests). Sub-analgesic doses of venlafaxine, tramadol, celecoxib and amlodipine were obtained using these methods. A sub-analgesic dose of venlafaxine was combined with sub-analgesic doses of tramadol, celecoxib and amlodipine to study their interactions. Results: The antinociceptive action of venlafaxine was found only at higher doses (10 and 22.5 mg/kg). When a sub-analgesic dose of venlafaxine was combined with sub-analgesic doses of tramadol, amlodipine or celecoxib, the combination resulted in a significant antinociceptive effect. Conclusion: Evidence of analgesic activity, as indicated by increase in tail flick latency and decrease in number of writhing movements following venlafaxine treatment, suggests that it could possibly have central as well as peripheral action. The findings indicate that the potential use of venlafaxine in antidepressant dose could produce marked pain relief. Thus patients of depression, who are on venlafaxine, may be able to tolerate mild to moderate pain without any additional analgesic.