Modification of tricyclic antidepressant analgesia by calcium channel blockers.

The influence of calcium channel blockers (CCB) on the analgesic activity of tricyclic antidepressants (TCA) was examined using hot plate (thermal) and writhing (chemical) method. Intraperitoneal injections of TCA, imipramine and amitriptyline or CCB viz: verapamil, nifedipine, nicardipine and cinnarizine per se produced analgesia. The Analgesic effect of TCA was further enhanced by prior treatment with CCB. The increase in TCA analgesia could not be ascribed to unitary mechanism but could possibly be mediated by opioid and/or nonopioid systems. These results clearly provide an evidence that a combination treatment of CCB and TCA may permit reduction of the TCA doses while treating chronic pain of organic origin.