These include itraconazole Sporanox, Tolsura , ketoconazole Extina, Ketozole, others and ritonavir Norvir. Oral ED medicines might not work or might be dangerous if you also take any of the following: Nitrate medicines. These medicines all work well for ED. Often, these are prescribed for chest pain called angina. When choosing one, tell your doctor or other health care professional what your preferences are, such as cost, ease of use, how long the drug’s effects last and side effects. It works for up to 36 hours. This medicine also works best when you take it an hour before sex on an empty stomach.It’s a prescription drug that’s used in adult males* with ED. With ED, you have trouble getting or keeping an erection. Viagra treats ED by increasing the amount Missing: nyc. SAVINGS Terms and conditions apply. take any medicines called nitrates, often prescribed for chest pain, or guanylate cyclase stimulators like Adempas (riociguat) for pulmonary Missing: nyc. Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or Missing: nyc.