EFFECT OF NIMODIPINE ON NOCICEPTIVE PAIN AND ITS INTERACTION WITH OPIOID ANALGESICS IN RATS

Objective: To explore the effect of nimodipine on nociception and on opioid-induced antinociception in rats by using the tail-flick method. Method: Sixty albino rats were used for the study. The tail-flick method was used to induce nociception in rats. Analgesic effect of nimodipine was evaluated by using three graded doses (200 mcg/kg, 400 mcg/kg, and 800 mcg/kg). To study the effect of nimodipine on opioid-induced antinociception, nimodipine (400 mcg/kg) was administered in combination with sub-effective doses of fentanyl and pethidine. Drugs were administered by intraperitoneal route. Results: Nimodipine at doses 200 mcg/kg, 400 mcg/kg, and 800 mcg/kg alone showed no significant difference in reaction times after 30 and 60 min as compared to baseline and control group. Similarly, effective sub doses fentanyl 15 mcg/kg and pethidine 10 mg/kg produced a non-significant increase in reaction times after 30 and 60 min as compared to baseline and control group. But the combination of nimodipine 400 mcg/kg and fentanyl 15 mcg/kg and the combination of nimodipine 400 mcg/kg and pethidine 10 mg/kg induced highly significant analgesia as compared to individual effect of the drugs. Conclusion: In the present study, no analgesic effect was observed with nimodipine alone, but the combination of nimodipine with opioids (fentanyl or pethidine) produced significantly greater analgesia suggesting a synergistic interaction between these drugs.