Nimodipine, sold under the brand name Nimotop among others, is a 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 termed vasospasm; this is now the main use of nimodipine. It was patented in 1971 and approved for medical use in the US in 1988. It was approved for medical use in Germany in 1985.
Medical use
Because it has some selectivity for cerebral vasculature, nimodipine's main use is in the prevention of cerebral vasospasm and resultant ischemia, a complication of subarachnoid hemorrhage, specifically from ruptured intracranial berry aneurysms irrespective of the patient's post-ictus neurological condition. Its administration begins within 4 days of a subarachnoid hemorrhage and is continued for three weeks. If blood pressure drops by over 5%, dosage is adjusted. There is still controversy regarding the use of intravenous nimodipine on a routine basis. A 2003 trial found nimodipine was inferior to magnesium sulfate in preventing seizures in women with severe preeclampsia. Nimodipine is not regularly used to treat head injury. Several investigations have been performed evaluating its use for traumatic subarachnoid hemorrhage; a systematic review of 4 trials did not suggest any significant benefit to the patients that receive nimodipine therapy. There was one report case of nimodipine being successfully used for treatment of ultradian bipolar cycling after brain injury and, later, amygdalohippocampectomy.
Dosage
The regular dosage is 60 mg tablets every four hours. If the patient is unable to take tablets orally, it was previously given via intravenous infusion at a rate of 1–2 mg/hour, but since the withdrawal of the IV preparation, administration by nasogastric tube is an alternative.
Contraindications
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. While nimodipine was occasionally administered intravenously in the past, the FDA released an alert in January 2006, warning that it had received reports of the approved oral preparation being used intravenously, leading to severe complications; this was despite warnings on the box that this should not be done.
After oral administration, it reaches peak plasma concentrations within one and a half hours. Patients taking enzyme-inducing anticonvulsants have lower plasma concentrations, while patients taking sodium valproate were markedly higher.
Studies in non-human mammals using radioactive labeling have found that 40–50% of the dose is excreted via urine. The residue level in the body was never more than 1.5% in monkeys.
The key acetoacetate for the synthesis of nimodipine is obtained by alkylation of sodium acetoacetate with 2-methoxyethyl chloride, Aldol condensation of meta-nitrobenzene and the subsequent reaction of the intermediate with enamine gives nimodipine.
Stereochemistry
Nimodipine contains a stereocenter and can exist as either of two enantiomers. The pharmaceutical drug is a racemate, an equal mixture of the - and - forms.
