fosphenytoin will decrease the level or effect of diazepam by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Observe.eslicarbazepine acetate will raise the level or impact of diazepam by affecting hepatic enzyme CYP2C19 metabolism. Use Warning/Watch.cyclophosphamide will enhance the degree or influence of diazepam by affecting h