Comparison of the direct negative dromotropic effect of a new calcium channel blocker, cilnidipine, with that of nicardipine.

We encountered a 91-year-old woman with atrial fibrillation complicating bradycardia while she was receiving therapy with an L/N-type calcium channel blocker, cilnidipine, for hypertension, which is an unusual observation for the dihydropyridine class of calcium channel blockers. Therefore, we compared the dromotropic effect of cilnidipine with that of an L-type calcium channel blocker, nicardipine, which has a similar hypotensive activity. The canine isolated, blood-perfused atrioventricular node preparation was used. Cilnidipine as well as nicardipine slowed atrioventricular nodal conduction in a dose-related manner. However, the dromotropic action of cilnidipine was about five times less potent than that of nicardipine. These experimental results may suggest that we experienced an atypical clinical event of cilnidipine in a very old woman; otherwise one can speculate that the N-type calcium channel inhibitory component of cilnidipine might have played a role in exerting the negative dromotropic effect in this patient.