Effect of intravenous flumazenil on oral midazolam pharmacokinetics and pharmacodynamics for use as a cytochrome P450 3A probe. 2009

J D Ma, and N M Lawendy, and T Fullerton, and P J Snyder, and A N Nafziger, and J S Bertino
Clinical Pharmacology Research Center, Bassett Healthcare, Cooperstown, NY, USA. joema@ucsd.edu

Phenotyping intestinal and hepatic cytochrome P450 (CYP) 3A activity with oral midazolam can be limited by midazolam-induced central nervous system (CNS) side effects. Determining methods to minimize CNS side effects optimizes use of midazolam as a CYP3A probe. OBJECTIVE The objective of this study was to determine the effect of intravenous (i.v.) flumazenil on midazolam apparent oral clearance (a surrogate marker of CYP3A activity). Midazolam pharmacodynamics were also evaluated. METHODS This was a randomized, double-blind, placebo-controlled, single-dose, two-way crossover study. 16 healthy volunteers (8 women) were concomitantly administered i.v. flumazenil 0.005 mg/kg or i.v. placebo and oral midazolam 0.075 mg/kg. Blood samples were obtained to determine midazolam and flumazenil plasma concentrations. Bioequivalence was assessed by determining geometric mean ratios (GMR) and 90% confidence intervals (90% CI). Baseline and post dose digit symbol substitution tests (DSST), Groton maze learning tests (GMLT), and Stanford sleepiness scales (SSS) were conducted. RESULTS Apparent oral clearance was 2,030 +/- 651 and 1,939 +/- 658 ml/min for the midazolam plus flumazenil and midazolam plus placebo groups. Equivalence in midazolam apparent oral clearance was observed (%GMR flumazenil/placebo, 90% CI 104.8, 94 - 116.6%). Flumazenil partially attenuated oral midazolam pharmacodynamics. Exploratory post hoc analyses revealed that midazolam exposure was 1.9-fold higher in men compared to women. CONCLUSIONS i.v. flumazenil can be used in conjunction with oral midazolam for CYP3A phenotyping.

UI MeSH Term Description Entries
D007275 Injections, Intravenous Injections made into a vein for therapeutic or experimental purposes. Intravenous Injections,Injection, Intravenous,Intravenous Injection
D008297 Male Males
D008874 Midazolam A short-acting hypnotic-sedative drug with anxiolytic and amnestic properties. It is used in dentistry, cardiac surgery, endoscopic procedures, as preanesthetic medication, and as an adjunct to local anesthesia. The short duration and cardiorespiratory stability makes it useful in poor-risk, elderly, and cardiac patients. It is water-soluble at pH less than 4 and lipid-soluble at physiological pH. Dormicum,Midazolam Hydrochloride,Midazolam Maleate,Ro 21-3981,Versed,Hydrochloride, Midazolam,Maleate, Midazolam,Ro 21 3981,Ro 213981
D008875 Middle Aged An adult aged 45 - 64 years. Middle Age
D009483 Neuropsychological Tests Tests designed to assess neurological function associated with certain behaviors. They are used in diagnosing brain dysfunction or damage and central nervous system disorders or injury. Aphasia Tests,Cognitive Test,Cognitive Testing,Cognitive Tests,Memory for Designs Test,Neuropsychological Testing,AX-CPT,Behavioral Assessment of Dysexecutive Syndrome,CANTAB,Cambridge Neuropsychological Test Automated Battery,Clock Test,Cognitive Function Scanner,Continuous Performance Task,Controlled Oral Word Association Test,Delis-Kaplan Executive Function System,Developmental Neuropsychological Assessment,Hooper Visual Organization Test,NEPSY,Neuropsychologic Tests,Neuropsychological Test,Paced Auditory Serial Addition Test,Repeatable Battery for the Assessment of Neuropsychological Status,Rey-Osterrieth Complex Figure,Symbol Digit Modalities Test,Test of Everyday Attention,Test, Neuropsychological,Tests, Neuropsychological,Tower of London Test,Neuropsychologic Test,Test, Cognitive,Testing, Cognitive,Testing, Neuropsychological,Tests, Cognitive
D010641 Phenotype The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment. Phenotypes
D004311 Double-Blind Method A method of studying a drug or procedure in which both the subjects and investigators are kept unaware of who is actually getting which specific treatment. Double-Masked Study,Double-Blind Study,Double-Masked Method,Double Blind Method,Double Blind Study,Double Masked Method,Double Masked Study,Double-Blind Methods,Double-Blind Studies,Double-Masked Methods,Double-Masked Studies,Method, Double-Blind,Method, Double-Masked,Methods, Double-Blind,Methods, Double-Masked,Studies, Double-Blind,Studies, Double-Masked,Study, Double-Blind,Study, Double-Masked
D004347 Drug Interactions The action of a drug that may affect the activity, metabolism, or toxicity of another drug. Drug Interaction,Interaction, Drug,Interactions, Drug
D005260 Female Females
D005442 Flumazenil A potent benzodiazepine receptor antagonist. Since it reverses the sedative and other actions of benzodiazepines, it has been suggested as an antidote to benzodiazepine overdoses. Flumazepil,Anexate,Lanexat,Ro 15-1788,Romazicon,Ro 15 1788,Ro 151788

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