Pharmacokinetics of nimodipine in patients with aneurysmal subarachnoid haemorrhage

Summary

Patients with a ruptured supratentorial aneurysm undergoing early surgery after the subarachnoid haemorrhage were treated postoperatively with nimodipine to prevent delayed ischaemic dysfunction. It was given first as a continuous intravenous infusion 2 mg/h (mean dose 0.5 µg/kg/min) for at least 7 days, and then orally (45 mg × 6) for at least a further 7 days. During the i.v. infusion, the mean plasma concentration was 26.6±1.8 ng/ml. The plasma clearance ranged from 0.57 to 1.77 l/kg/h and was negatively correlated with the age of the patient. Immediately prior to successive oral doses, the mean plasma concentration was 13.2 ng/ml (range<3–38.8 ng/ml). The peak level was usually found after 1 h; it ranged from 7.0–96.0 ng/ml. Mean bioavailability was 15.9%. The nitropyridine metabolite was found in measurable concentrations only after oral treatment with nimodipine. In some cases, the concentration of metabolite exceeded that of the parent compound. The three patients investigated who developed delayed ischaemic dysfunction had plasma concentrations well within the range in patients who did not, so it seems unlikely that the therapeutic failure could be attributed to individual deviations in the pharmacokinetics of the drug.