Comparative analgesic effects of morphine, buprenorphine and nifedipine and their interactions in mice.

摘要

Buprenorphine, a partial agonist analgesic, and nifedipine, a calcium channel blocker, were subjected to drug studies with morphine, an opioid analgesic. 27 groups of mice of 6 animals per group, 25-0 g, were used in the study. The analgesic effect was assessed by the mouse tail immersion assay. 100% analgesia was observed with 8 mg/kg morphine, 40 mg/kg buprenophine and 30 mg/kg nifedipine. The order of decreasing potency of the 3 drugs was buprenorphine, morphine and nifedipine. The peak anti-nociceptive effect was at 30 min after morphine and buprenorphine administrations. The peak anti-nociceptive activity of nifedipine was 40 min after administration. The subanalgesic dose of nifedipine (0.3125 mg/kg) potentiated the anti-nociceptive activity of buprenorphine (4 micro g/kg; lower dose) significantly by 230%. Similarly, nifedipine pretreatment enhanced the anti-nociceptive activity of 40 960 micro g/kg (higher dose) by 208%. Buprenorphine (10 micro g/kg) anti-nociception was not reversed by nalaxone but nalaxone pretreatment significantly reduced the anti-nociceptive effect of nifedipine (10 mg/kg). Nalaxone pretreatment significantly increased the anti-nociceptive effect of 1.25 micro g/kg nifedipine..