Nimodipine Capsules For Oral Use Rx only

Nimodipine is a calcium channel blocker.  The contractile processes of smooth muscle cells are dependent upon calcium ions, which enter these cells during depolarization as slow ionic transmembrane currents.  Nimodipine inhibits calcium ion transfer into these cells and thus inhibits contractions of vascular smooth muscle.  In animal experiments, nimodipine had a greater effect on cerebral arteries than on arteries elsewhere in the body perhaps because it is highly lipophilic, allowing it to cross the blood-brain barrier; concentrations of nimodipine as high as 12.5 ng/mL have been detected in the cerebrospinal fluid of nimodipine-treated subarachnoid hemorrhage (SAH) patients.

The precise mechanism of action of nimodipine in humans is unknown.  Although the clinical studies described below demonstrate a favorable effect of nimodipine on the severity of neurological deficits caused by cerebral vasospasm following SAH, there is no arteriographic evidence that the drug either prevents or relieves the spasm of these arteries.  However, whether or not the arteriographic methodology utilized was adequate to detect a clinically meaningful effect, if any, on vasospasm is unknown.

In man, nimodipine is rapidly absorbed after oral administration, and peak concentrations are generally attained within one hour.  The terminal elimination half-life is approximately 8 to 9 hours but earlier elimination rates are much more rapid, equivalent to a half-life of 1-2 hours; a consequence is the need for frequent (every 4 hours) dosing.  There were no signs of accumulation when nimodipine was given three times a day for seven days.  Nimodipine is over 95% bound to plasma proteins.  The binding was concentration independent over the range of 10 ng/mL to 10 µg/ml. Nimodipine is eliminated almost exclusively in the form of metabolites and less than 1% is recovered in the urine as unchanged drug.  Numerous metabolites, all of which are either inactive or considerably less active than the parent compound, have been identified.  The metabolism of nimodipine is mediated by CYP3A4. Because of a high first-pass metabolism, the bioavailability of nimodipine averages 13% after oral administration. The bioavailability is significantly increased in patients with hepatic cirrhosis, with Cmax approximately double that in normals which necessitates lowering the dose in this group of patients (see DOSAGE AND ADMINISTRATION).  In a study of 24 healthy male volunteers, administration of nimodipine capsules following a standard breakfast resulted in a 68% lower peak plasma concentration and 38% lower bioavailability relative to dosing under fasted conditions.

In a single parallel-group study involving 24 elderly subjects (aged 59-79) and 24 younger subjects (aged 22-40), the observed AUC and Cmax of nimodipine was approximately 2-fold higher in the elderly population compared to the younger study subjects following oral administration (given as a single dose of 30 mg and dosed to steady-state with 30 mg t.i.d. for 6 days).  The clinical response to these age-related pharmacokinetic differences, however, was not considered significant. (See PRECAUTIONS, Geriatric Use.)

Nimodipine has been shown, in 4 randomized, double-blind, placebo-controlled trials, to reduce the severity of neurological deficits resulting from vasospasm in patients who have had a recent subarachnoid hemorrhage (SAH).  The trials used doses ranging from 20-30 mg to 90 mg every 4 hours, with drug given for 21 days in 3 studies, and for at least 18 days in the other.  Three of the four trials followed patients for 3-6 months.  Three of the trials studied relatively well patients, with all or most patients in Hunt and Hess Grades I - III (essentially free of focal deficits after the initial bleed) the fourth studied much sicker patients, Hunt and Hess Grades III - V.  Two studies, one U.S., one French, were similar in design, with relatively unimpaired SAH patients randomized to nimodipine or placebo.  In each, a judgment was made as to whether any late-developing deficit was due to spasm or other causes, and the deficits were graded.  Both studies showed significantly fewer severe deficits due to spasm in the nimodipine group; the second (French) study showed fewer spasm-related deficits of all severities.  No effect was seen on deficits not related to spasm.

A third, large, study was performed in the United Kingdom in SAH patients with all grades of severity (but 89% were in Grades I-III).  Nimodipine was dosed 60 mg every 4 hours.  Outcomes were not defined as spasm related or not but there was a significant reduction in the overall rate of infarction and severely disabling neurological outcome at 3 months:

A Canadian study entered much sicker patients, (Hunt and Hess Grades III-V), who had a high rate of death and disability, and used a dose of 90 mg every 4 hours, but was otherwise similar to the first two studies.  Analysis of delayed ischemic deficits, many of which result from spasm, showed a significant reduction in spasm-related deficits.  Among analyzed patients (72 nimodipine, 82 placebo), there were the following outcomes.

When data were combined for the Canadian and the United Kingdom studies, the treatment difference on success rate (i.e., good recovery) on the Glasgow Outcome Scale was 25.3% (nimodipine) versus 10.9% (placebo) for Hunt and Hess Grades IV or V.  The table below demonstrates that nimodipine tends to improve good recovery of SAH patients with poor neurological status post-ictus, while decreasing the numbers with severe disability and vegetative survival.

A dose-ranging study comparing 30, 60 and 90 mg doses found a generally low rate of spasm-related neurological deficits but no dose response relationship.

Blood Pressure:  Nimodipine has the hemodynamic effects expected of a calcium channel blocker, although they are generally not marked.  However, intravenous administration of the contents of nimodipine capsules has resulted in serious adverse consequences including death, cardiac arrest, cardiovascular collapse, hypotension, and bradycardia.  In patients with subarachnoid hemorrhage given nimodipine in clinical studies, about 5% were reported to have had lowering of the blood pressure and about 1% left the study because of this (not all could be attributed to nimodipine).  Nevertheless, blood pressure should be carefully monitored during treatment with nimodipine based on its known pharmacology and the known effects of calcium channel blockers. (see WARNINGS and DOSAGE AND ADMINISTRATION).

Hepatic Disease: The metabolism of nimodipine is decreased in patients with impaired hepatic function. Such patients should have their blood pressure and pulse rate monitored closely and should be given a lower dose (see DOSAGE AND ADMINISTRATION).

Intestinal pseudo-obstruction and ileus have been reported rarely in patients treated with nimodipine.  A causal relationship has not been established.  The condition has responded to conservative management.

None known.

Nimodipine is metabolized via the cytochrome P450 3A4 system located both in the intestinal mucosa and in the liver.  Drugs that are known to either inhibit or to induce this enzyme system may therefore alter the first pass or the clearance of nimodipine.

In addition, the blood pressure lowering effects of antihypertensives could be enhanced when taken concomitantly with nimodipine.

In a two-year study, higher incidences of adenocarcinoma of the uterus and Leydig-cell adenoma of the testes were observed in rats given a diet containing 1800 ppm nimodipine (equivalent to 91 to 121 mg/kg/day nimodipine) than in placebo controls.  The differences were not statistically significant, however, and the higher rates were well within historical control range for these tumors in the Wistar strain.  Nimodipine was found not to be carcinogenic in a 91-week mouse study but the high dose of 1800 ppm nimodipine-in-feed (546 to 774 mg/kg/day) shortened the life expectancy of the animals.  Mutagenicity studies, including the Ames, micronucleus and dominant lethal tests were negative.

Nimodipine did not impair the fertility and general reproductive performance of male and female Wistar rats following oral doses of up to 30 mg/kg/day when administered daily for more than 10 weeks in the males and 3 weeks in the females prior to mating and continued to day 7 of pregnancy.  This dose in a rat is about 4 times the equivalent clinical dose of 60 mg q4h in a 50 kg patient.

Pregnancy Category C.  Nimodipine has been shown to have a teratogenic effect in Himalayan rabbits.  Incidences of malformations and stunted fetuses were increased at oral doses of 1 and 10 mg/kg/day administered (by gavage) from day 6 through day 18 of pregnancy but not at 3 mg/kg/day in one of two identical rabbit studies.  In the second study an increased incidence of stunted fetuses was seen at 1 mg/kg/day but not at higher doses.  Nimodipine was embryotoxic, causing resorption and stunted growth of fetuses, in Long Evans rats at 100 mg/kg/day administered by gavage from day 6 through day 15 of pregnancy.  In two other rat studies, doses of 30 mg/kg/day nimodipine administered by gavage from day 16 of gestation and continued until sacrifice (day 20 of pregnancy or day 21 post partum) were associated with higher incidences of skeletal variation, stunted fetuses and stillbirths but no malformations.  There are no adequate and well controlled studies in pregnant women to directly assess the effect on human fetuses. Nimodipine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Nimodipine and/or its metabolites have been shown to appear in rat milk at concentrations much higher than in maternal plasma. It is not known whether the drug is excreted in human milk. Because many drugs are excreted in human milk, nursing mothers are advised not to breast feed their babies when taking the drug.

Safety and effectiveness in children have not been established.

Clinical studies of nimodipine did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects.  Other reported clinical experience has not identified differences in responses between the elderly and younger patients.  In general, dosing in elderly patients should be cautious, reflecting the greater frequency of decreased hepatic, renal or cardiac function, and of concomitant disease or other drug therapy.