Patients taking isosorbide tablets should not take sildenafil. 1. The main effect of isosorbide tablets is to dilate blood vessels, mainly on the coronary artery expansion is more obvious, but also on the peripheral blood vessels have a certain dilatation effect, some patients are more sensitive, after taking the drug may appear to drop the level of blood pressure. 2. The main effect of sildenafil is to dilate the peripheral blood vessels, can make the penis congested, increase the hardness of the penis erection, prolong the time of erection. Isosorbide tablets and sildenafil both have vasodilating effects, and their simultaneous use may lead to a significant increase in vasodilating effects, causing patients to experience a serious drop in blood pressure, such as dizziness or even fainting symptoms. Sildenafil is not recommended at any time for patients taking oral isosorbide tablets to avoid serious adverse events. Adverse effects of isosorbide include upright hypotension, dizziness, reactive tachycardia, etc. In severe cases, syncope can occur, and the drug is contraindicated in patients with allergy to drug components, glaucoma, cardiogenic shock, hypertrophic obstructive cardiomyopathy, and elevated intracranial pressure. Adverse reactions to sildenafil include dyspnea, bradycardia, edema, gastritis, accidental falls, etc. It is contraindicated in patients who are allergic to the components of the drug and female patients. When using medication, it is important to follow the doctor’s instructions, rational application of drugs, do not use drugs arbitrarily, to avoid causing serious side effects as well as adverse reactions.