title: Pharmacokinetic-pharmacodynamic modeling of midazolam effects on the human central nervous system.
abstract: The effect of midazolam on alpha-activity of the EEG and latency of the P-100 of the visual evoked response (VER) was studied in six healthy subjects. Drug concentration was related to effect with the Emax model that was used with either a threshold drug concentration or a sigmoid exponent. An effect compartment was included in the pharmacokinetic-pharmacodynamic model. Four subjects showed hysteresis, and mean values of half-lives-k(eo) ranged from 0.26 to 0.60 hour. Mean values of EC50 ranged from 42.0 to 48.1 ng/ml. Goodness of fit did not differ significantly between the sigmoid Emax model and the threshold Emax model. The sigmoid exponent estimated was 3.7 +/- 1.8 (EEG, mean +/- SD) and 2.9 +/- 1.4 (VER); the threshold concentration was estimated at 15.7 +/- 11.1 ng/ml (EEG) and 11.3 +/- 7.0 ng/ml (VER). We conclude that the Emax model adequately describes the relationship between midazolam concentration and effect and that the sigmoid exponent can be substituted by a threshold drug concentration, with a comparable fit of the model to the data.
authors.affiliation: Department of Medicine, University of Amsterdam, The Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: Koopmans
authors.forename: J
authors.initials: J
authors.lastname: Dingemanse
authors.forename: M
authors.initials: M
authors.lastname: Danhof
authors.forename: G P
authors.initials: GP
authors.lastname: Horsten
authors.forename: C J
authors.initials: CJ
authors.lastname: van Boxtel
mesh_terms: D002490:Central Nervous System / Q000187:drug effects* / Q000502:physiology; D003627:Data Interpretation, Statistical; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000187:drug effects; D006801:Humans; D008874:Midazolam / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology; D008954:Models, Biological
chemical_list: D008874:Midazolam