Clinical experience with the benzodiazepine antagonist flumazenil in suspected benzodiazepine or ethanol poisoning

Abstract

The clinical efficacy of different doses of the specific benzodiazepine antagonist flumazenil was studied in a total of 72 patients with benzodiazepine or ethanol overdose. In a randomized double-blind study, 18 patients (group 1) and eight patients (group 2) with suspected flumazenil or placebo, respectively. The stage of coma, heart rate, blood pressure and respiratory rate were monitored within the following 15 min. If no change in the stage of coma was observed, 5 mg (group 1) or 1 mg (group 2) flumazenil were given, and the stage of coma, heart rate and blood pressure were again monitored. In an similar way, the effect of 5 and 1 mg flumazenil was investigated in 13 patients (group 3) and four patients (group 4) with ethanol intoxication. In an open trial, the clinical efficacy of flumazenil for the diagnosis of benzodiazepine or ethanol overdose was studied in 29 patients (group 5). In all patients, a toxicological screening confirmed benzodiazepine or ethanol overdose. None of the patients receiving placebo showed effects on stage of coma, heart rate, blood pressure or respiratory rate. Patients with benzodiazepine overdose who received 5 mg flumazenil regained consciousness about 1-2 min after the end of injection. The effect of 1 mg flumazenil (group 2) on benzodiazepine-induced coma was less pronounced. In patients with ethanol overdose (group 3), ethanol-induced coma was reversed after 5 mg flumazenil more slowly than in patients of group 1. No effect of flumazenil on ethanol-induced coma was observed in group 4. In group 5, flumazenil proved to be useful for diagnosing benzodiazepine or ethanol intoxication. In one patient with coma due to carbamazepine overdose, flumazenil was also found to be effective.

Additionally, a possible analytical interference of flumazenil and its metabolites with the identification of other benzodiazepines by a toxicological screening procedure was studied. Even after an oral dose of 200 mg flumazenil, no interference with immunological benzodiazepine assays (EMIT, TDX, and RIA) was found. A metabolite and an artifact of flumazenil could be identified in urine by gas chromatography/mass spectrometry.