The mechanism of action of Ca2+ antagonists, such as verapamil and nifedipine, has been postulated to be a blockade of transmembrane calcium influx.
In this study, the vasodilating effect of diltiazem on experimental cerebral vasospasm in vivo was examined using dogs and compared with those of cinnarizine, verapamil and nifedipine which have already been reported by us. Cerebral vasospasms were induced in adult dogs by injecting 5 ml of fresh arterial blood into the cisterna magna. 10-6M diltiazem was injected by one shot into the vertebral artery of the dogs with cerebral vasospasm. Dilatation of the cerebral arteries was observed by angiography after administration of diltiazem. Blood pressure, intracranial pressure and pulse rate were measured during intravenous application of the drug in normal dogs.
Administration of diltiazem released the vasospasm for 30 minutes, comparable to the times of the other Ca2+ antagonists. Diltiazem had cerebral vasodilator actions similar to cinnarizine at doses that did not decrease systemic blood pressure, while the other drugs increased intracranial pressure slightly. Therefore, we consider diltiazem to be satisfactory for the treatment of experimental cerebral vasospasm.
