Purpose: A pharmacokinetic study in children to determine plasma flumazenil concentrations after the intranasal administration of 40 microg x kg(-1).
Methods: Following institutional approval and informed written consent, 11 ASA physical status I-II patients, aged two to six years, undergoing general anesthesia for dental surgery were recruited. After induction, 40 microg x kg(-1) flumazenil Anexate, Roche, 0.1 mg x mL(-1) (0.4 mL x kg(-1))) were administered via a syringe as drops, prior to nasal intubation. Venous plasma samples were drawn prior to administration of flumazenil (t = 0), and then at 2, 4, 6, 8, 10, 15, 20, 30, 40, 60, and 120 min thereafter. The plasma samples were immediately processed by the on-site laboratory and then stored at -70 degrees C, before batch analysis via high performance liquid chromatography assay. Pharmacokinetic data calculations were performed using WinNonLin software (Scientific Consulting Inc.).
Results: Eleven patients were studied, but data for one patient were discarded due to insufficient sampling. The median age was 4.3 yr (range 3 to 6), with a median weight of 18.9 kg (range 14.9 to 22.2). There were seven boys and three girls. Mean Cmax was 67.8 ng x mL(-1) (SD 41.9), with Tmax at two minutes. The calculated half-life was 122 min (SD 99).
Conclusion: The mean plasma concentrations of flumazenil attained were similar to those reported after intravenous administration, and may be sufficient to antagonize the side-effects of benzodiazepines. This route of administration may be useful when the intravenous route is not readily available.