CSF penetration and pharmacokinetics of midazolam.

Abstract

The passage of midazolam, a new benzodiazepine derivative with highly water-soluble salts, into cerebrospinal fluid (CSF) was studied after a single oral dose of 15 mg (n=23), a single i.m. injection of 0.075 or 0.150 mg/kg (n=8), or a single i.v. dose of 0.075 mg/kg (n=26). Contrary to previous studies of diazepam and flunitrazepam, the rapid clinical effect of midazolam cannot be explained by rapid passage into human lumbar CSF. In only four cases following intravenous injection was there a measurable amount of drug in lumbar CSF (lower limit of assay sensitivity=2 ng/ml). After both oral (n=10) and intramuscular (n=8) administration, midazolam was rapidly absorbed, with attainment of the peak serum level after about 0.5 h. The pharmacokinetic parameters following i.v. injection of midazolam (n=6) explain its rapid but brief duration of action.