Medicines that block an enzyme called CYP3A4. Sildenafil Liqrev, Revatio is used to improve the ability to exercise in adults Liqrev, Revatio and children 1 year of age and older Revatio with pulmonary arterial hypertension PAH; high blood pressure in the vessels carrying blood to the lungs, causing shortness of breath, dizziness, and tiredness. Before starting, stopping, or changing any medications while taking sildenafil, please get the advice of your doctor or pharmacist. When oral medications might not be safe Check with your health care team before you take any medicine for erectile dysfunction. These include itraconazole Sporanox, Tolsura , ketoconazole Extina, Ketozole, others and ritonavir Norvir. Brand names Why is this medication prescribed?VIAGRA can cause your blood pressure to drop suddenly to an unsafe level if taken with certain other medicines. Do not take VIAGRA if you take any other medicines called “nitrates.” Nitrates are used to treat chest pain (angina). A sudden drop in blood pressure can cause you to feel dizzy, faint, or have a heart attack or stroke. According to price-comparison site , generic Revatio will cost you as little as $ per pill, depending on where you fill your prescription. That’s compared with more than $50 per. What to do in case you take too much Viagra Call your doctor if you think you’ve taken too much Viagra. You can also call to reach the American Association of Poison Control Centers.