indication

For the complete or partial reversal of the sedative effects of benzodiazepines in cases where general anesthesia has been induced and/or maintained with benzodiazepines, and where sedation has been produced with benzodiazepines for diagnostic and therapeutic procedures. Also for the management of benzodiazepine overdose as an adjunct for appropriate supportive and symptomatic measures.

pharmacology

Flumazenil antagonizes the CNS effects produced by benzodiazepines, but does not antagonize the central nervous system effects of drugs affecting GABA-ergic neurons by means other than the benzodiazepine receptor (including ethanol, barbiturates, or general anesthetics) and does not reverse the effects of opioids.

mechanism of action

Flumazenil, an imidazobenzodiazepine derivative, antagonizes the actions of benzodiazepines on the central nervous system. Flumazenil competitively inhibits the activity at the benzodiazepine recognition site on the GABA/benzodiazepine receptor complex. Flumazenil is a weak partial agonist in some animal models of activity, but has little or no agonist activity in man.

toxicity

In clinical studies, most adverse reactions to flumazenil were an extension of the pharmacologic effects of the drug in reversing benzodiazepine effects.

biotransformation

Hepatic. Flumazenil is completely (99%) metabolized. The major metabolites of flumazenil identified in urine are the de-ethylated free acid and its glucuronide conjugate.

half life

Initial distribution half-life is 4 to 11 minutes and the terminal half-life is 40 to 80 minutes. Prolongation of the half-life to 1.3 hours in patients with moderate hepatic impairment and 2.4 hours in severely impaired patients. Compared to adults, the elimination half-life in pediatric patients was more variable, averaging 40 minutes (range: 20 to 75 minutes).

route of elimination

Flumazenil is completely (99%) metabolized. Elimination of radiolabeled drug is essentially complete within 72 hours, with 90% to 95% of the radioactivity appearing in urine and 5% to 10% in the feces.