fosphenytoin will lower the level or result of diazepam by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Use Warning/Check.oxcarbazepine will lessen the level or effect of diazepam by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Use Warning/Check.Concomitant use of benzodiazepines and opioids may result in profound sedation,