primidone will lower the extent or effect of diazepam by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Check.fosphenytoin will minimize the extent or effect of diazepam by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Keep track of.There are plenty of variables that have an affect on how long Valium remai