Interactions of benzodiazepines with warfarin.

Administration of nitrazepam (10 mg nightly), diazepam (15 mg/day), and chlordiazepoxide (15 and 30 mg/day) had no effect on steady-state plasma warfarin concentrations, the plasma half-life of warfarin, or anticoagulant control in patients and it appears safe to prescribe these agents to patients on long-term oral anticoagulants. Urinary excretion of 6 beta-hydroxycortisol, however, increased in two out of five patients given chlordiazepoxide. In rats pretreatment with chlordiazepoxide (40 mg/kg for four days) caused stimulation of liver microsomal enzyme activity but neither diazepam nor nitrazepam had this effect.