title: Interaction between flumazenil and the anesthetic effects of hexobarbital in the rat.
abstract: Interaction between flumazenil, a substance regarded mainly as a benzodiazepine antagonist, and an intravenous anesthetic barbiturate, hexobarbital, was investigated by using an electroencephalography threshold test in male rats. Flumazenil 10 mg/kg given as pretreatment reduced the threshold dose of hexobarbital approximately 20% indicating a synergistic interaction. Similar effects were obtained with the agonists, diazepam 20 mg/kg and lorazepam 2 mg/kg. Dose-response curve for flumazenil (2.5-10 mg/kg) was determined with the same technique and hexobarbital concentrations were analysed in serum and several brain regions at the threshold by high pressure liquid chromatography. Flumazenil 10 mg/kg pretreated group showed a different pattern of distribution of hexobarbital into the tested brain regions indicating a pharmacokinetic interaction. Low concentrations of hexobarbital in the brainstem which were negatively correlated with the dose of flumazenil indicate a pharmacodynamic interaction which could be due to partial agonistic intrinsic activity of flumazenil, usually seen at much higher doses.
authors.affiliation: Department of Pharmacology, Umeå University, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Korkmaz
authors.forename: E
authors.initials: E
authors.lastname: Ljungblad
authors.forename: G
authors.initials: G
authors.lastname: Wahlström
mesh_terms: D000704:Analysis of Variance; D000777:Anesthetics; D000818:Animals; D004357:Drug Synergism; D004569:Electroencephalography; D005442:Flumazenil / Q000494:pharmacology*; D006591:Hexobarbital / Q000494:pharmacology*; D008297:Male; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000777:Anesthetics; D005442:Flumazenil; D006591:Hexobarbital