[Antagonism of the effects of benzodiazepines using flumazenil (Ro 15-1788)]

Flumazenil (Ro 15-1788) proved to be a very efficacious competitive antagonist of benzodiazepines that reliably counteracts their pharmacological actions within 1-2 min as could be demonstrated in clinical and EEG studies. In general, a total dose of 0.3-0.8 mg will be sufficient in clinical practice, avoiding side effects like nausea, tremor, sweating, or transient anxiety that could be observed when higher dosages were administered. Its therapeutic range is very high as could be demonstrated in experimental animal in which up to 8.000-fold the clinical dose was administered. The total volume of distribution (Vdes) amounts to nearly 1.000 ml/kg BW and the total clearance exceeds 1.200 ml/min, resulting in a biological half-life of less than 60 min. According to the benzodiazepine dosage and the rapid plasma concentration decline of flumazenil, in some cases a resedation could be observed. Hence, a careful observation of the antagonised patient on the ward is mandatory for 1.5-2 h, even if at first sight the antagonization seemed successful and the patient fully awake and cooperative. In anaesthesia, indications to administer flumazenil are adverse drug reactions and prolonged recovery after adequate benzodiazepine dosage. In intensive care medicine, the antagonist may be used in the treatment of benzodiazepine overdose as well as in the differential diagnosis of a coma of unknown origin. Additionally, the antagonist may be administered to interrupt benzodiazepine sedation e.g. for neurological examination.