primidone will lessen the extent or effect of diazepam by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.verapamil will enhance the degree or effect of diazepam by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Valium is detectable in blood for 6 to forty eight hrs. Blood exams are generally