(pharmacology) A short-acting benzodiazepine derivative with relatively long-lasting sedative effects, used as a hypnotic and as a premedication for anesthesia; 5-(2-fluorophenyl)-1,3-dihydro-1-methyl-7-nitro-2H-1,4-benzodiazepin-2-one, C₁₆H₁₂FN₃O₃.