<s>[INST] context: Calcium Channel Blockers (CCBs) These are the drugs that block L-type of voltage gated calcium channels present in blood vessels and hea. Three groups of CCBs include phenylalkylamines (verapamil, nor-verapamil), benzothiazepines (diltiazem) dihydropyridines (nifedipine, nicardipine, nimodipine, nisoldipine, nitrendipine, isradipine, lacidipine, felodipine and amlodipine). By inhibiting the calcium channels, these agents result in vasodilation and decreased activity of the hea (decrease hea rate, AV conduction and contractility). Dihydropyridine (DHP) group has little direct cardiac activity and acts mainly on blood vessels, therefore are also called peripherally acting CCBs. Verapamil and diltiazem have strong direct cardiodepressant (verapamil > diltiazem) activity. CCBs tend to cause reflex tachycardia (because of their vasodilatory action), which is nullified by the direct depressant action on the hea (except DHPs). Nicardipine is longest acting parenteral calcium channel blocker and is drug of choice for hypeensive emergencies. It is combined with beta blockers to avoid tachycardia. Nimodipine is a relatively cerebro-selective vasodilator, thus used to reverse the compensatory vasoconstriction after sub-arachnoid hemorrhage. Verapamil has maximum depressant action on the hea and it causes vasodilation by causing blockade of calcium channel. It is indicated for the treatment of angina, PSVT, hypeension and hyperophic obstructive cardiomyopathy (HOCM). Diltiazem has lesser effect on the hea than verapamil and is also indicated for these conditions. CCBs are especially suitable for elderly patients, patients with low renin hypeension, patients with diseases like asthma, migraine or peripheral vascular disease and in cases of isolated systolic hypeension. DHPs are safe in pregnancy. CCBs (verapamil and diltiazem) should be avoided in conditions involving decreased conductivity of the hea like sick sinus syndrome, CHF and along with beta blockers (both cause myocardial depression). Clevidipine is an ultrasho acting DHP, recently approved for hypeensive emergencies. [/INST] question: Which of the following drug is used for reversal of cerebral vasospasm and infarct following subarachnoid hemorrhage? | options: A: Nimodipine B: Amlodipine C: Diltiazem D: Verapamil | answer: A </s>