Oral ED medicines might not work or might be dangerous if you also take any of the following: Nitrate medicines. Medicines that block an enzyme called CYP3A4. These are commonly prescribed for an enlarged prostate or male pattern baldness. These include itraconazole Sporanox, Tolsura , ketoconazole Extina, Ketozole, others and ritonavir Norvir. This medicine works best when you take it on an empty stomach an hour before sex. These medicines all work well for ED.According to price-comparison site test1.ru, generic Revatio will cost you as little as $ per pill, depending on where you fill your prescription. That’s . Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes muscles in the penis, called nitric oxide. This boosts blood flow and helps you get an erection from sexual activity. According to price-comparison site test1.ru, 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.