Potent, selective and competitive benzodiazepine receptor antagonist (IC50 values are 0.4 and 0.7 nM for inhibition of [3H]-flunitrazepam binding to rat cerebellum and hippocampus respectively). Similar in vivo profile to flumazenil (Ro 15-1788, Cat No. 1328); produces anxiogenic effects in some behavioral tests and anxiolytic effects in others. Orally active.