• M M Ghoneim, R I Block, S T Ping, H M el-Zahaby, and J V Hinrichs.
• Department of Anesthesia, University of Iowa, Iowa City.
• Anesthesiology. 1993 Dec 1; 79 (6): 1183-92.

BackgroundPrevious research has been unable to show unequivocally whether flumazenil can reverse completely, partially, or not at all the memory effects of benzodiazepines. The effects of midazolam on implicit memory are also unknown. The behavioral effects of flumazenil by itself, and the acute reversal of benzodiazepine effects, are also controversial. The current study was designed to investigate these questions.MethodsUsing a prospective randomized, double-blind crossover study design, memory was assessed using both direct (free recall and recognition) and indirect (word completion) measures. Other cognitive effects were assessed using the digit symbol substitution task. Sedation and other mood effects were assessed using subjective rating scales. Seventy-two healthy subjects were assigned to three equal groups according to the dose of midazolam received (0, 0.05, and 0.1 mg/kg). Each subject received varying doses of flumazenil (0, 1, and 3 mg) in three sessions, at least 1 week apart. After baseline administration of the tasks, midazolam was administered. The assessments were repeated 20 min later, followed by administration of flumazenil. The assessments were repeated 5 and 30 min after administration of flumazenil. After a 2-h recovery period, delayed memory tests were given.ResultsBoth doses of midazolam decreased all scores in the memory and digit symbol substitution tests and mood ratings. Flumazenil reversed both the sedative and the memory effects of the benzodiazepine. The reversal was as complete with the 1-mg dose of flumazenil as with the 3-mg dose. Flumazenil by itself, and the acute reversal of midazolam effects, caused no significant behavioral reactions.ConclusionsMidazolam impairs explicit and implicit memory. Flumazenil reverses both the sedative and memory effects of the drug. Flumazenil, in the doses used, has no intrinsic actions.

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