Some people may ask, "What is trandolapril-verapamil ER used for?" Trandolapril-verapamil ER is used to control high blood pressure in adults. Trandolapril-verapamil ER is a combination of two medications. Because of the effects of both medicines, trandolapril-verapamil ER can cause a greater drop in blood pressure than when either medication is used alone. Trandolapril-verapamil ER has not been approved for use in children and there are currently no universally accepted off-label uses for this medication.