There are a number of potential drug interactions with trandolapril-verapamil ER. Among other things, trandolapril-verapamil ER drug interactions can cause your blood pressure to decrease too much, contribute to kidney damage in some people, and lead to side effects like headaches and dizziness. Some of the drugs that can potentially interact with trandolapril-verapamil ER include neuromuscular blocking agents; potassium-sparing diuretics, such as spironolactone, triamterene, and amiloride; and beta blockers, such as metoprolol, propranolol, atenolol.