It might work longer if you have mild to moderate erectile dysfunction. 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. These include itraconazole Sporanox, Tolsura , ketoconazole Extina, Ketozole, others and ritonavir Norvir. Rarely reported side effects include: an erection that will not go away priapism. Medicines that block an enzyme called CYP3A4.Sildenafil. Switch to brand medication. info_outlined. Used for Erectile Dysfunction. MORE expand_more. Check your prescription. Prescription mg sildenafil (30 tablets) edit. Choose your pharmacy. moses lake, WA. Safeway. Walgreens. Rite Aid. info How to use this coupon. phone Need help? Pick the price that’s right for you. Currently, there are no over the counter alternatives to Viagra available. Viagra (sildenafil) is a prescription medication, meaning it’s not available over the counter from your. In the United States, sildenafil for ED or PH requires a prescription. The United Kingdom allows for over-the-counter (OTC) sales of the drug, in part to discourage the market for fake.