Pharmacologic inhibition of cerebral vasospasm in ischemia, hallucinogen ingestion, and hypomagnesemia: barbiturates, calcium antagonists, and magnesium.

Experiments indicate that several different calcium antagonists have vasodilatory properties which may be expressed selectively on different organ vascular beds. Verapamil was most active as a vasodilator in muscular microvasculature. Cerebral venules are most sensitive to nimodipine. Nisoldipine is inactive in cerebral vascular dilation. We have also studied the vasodilatory effects of several barbiturates. Pentobarbital is the most active cerebrovasodilator in this class of anesthetics. This agent inhibits the vasospastic activity of potassium, serotonin, and prostaglandins, and appears to be a calcium entry antagonist in vasculature. The hallucinogens phencyclidine, mescaline, and LSD all induce cerebral vasospasm. This can be either blocked or reversed with calcium antagonists. Magnesium is a competitive calcium antagonist, and alterations in the extracellular content of this ion have profound effects on cerebral vascular resistance.