How do ED drugs interact?
Sildenafil, tadalafil and vardenafil are drugs that cause the dilation of blood vessels (vasodilators) and this effect can be magnified when they are used with other medications with similar vasodilating effects. It is this vasodilating effect that increases blood flow to the penis causing an erection. Most ED drug interactions, however, result from the fact that these drugs are metabolized by the enzyme CYP3A4 in the intestine and liver. CYP3A4 is the most important enzyme for drug metabolism, and many medications can interact with ED drugs by decreasing or increasing CYP3A4 activity, causing ED drug levels to increase or decrease, respectively. Interactions with vasodilators People who take nitrates (drugs commonly used to dilate the blood vessels in the heart for patients with coronary artery disease, such as nitroglycerin), either on a regular schedule or as needed, should not use these ED drugs. A dangerous reduction in blood pressure may occur, potentially leading to a heart atta
