Nimodipine is a dihydropyridine calcium channel blocker originally developed for the treatment of high blood pressure. It is not frequently used for this indication, but has shown good results in preventing a major complication of subarachnoid hemorrhage (a form of cerebral hemorrhage) termed vasospasm; this is now the main use of nimodipine. Nimodipine is metabolized in the first pass metabolism. The dihydropyridine ring of the nimodipine is dehydrogenated in the hepatic cells of the liver, a process governed by Cytochrome P-4503A (CYP3A). This can be completely inhibited however, by troleandomycin or ketoconazole. Nimodipine is associated with low blood pressure, flushing and sweating, edema, nausea and other gastrointestinal problems, most of which are known characteristics of calcium channel blockers. It is contraindicated in unstable angina or an episode of myocardial infarction more recently than one month.