What Are the Symptoms of Erectile Dysfunction? This increase in blood flow results in a firmer, longer-lasting erection. Medical consultations were also taken into consideration, as PDE5 inhibitors require a valid prescription from a licensed medical provider. These include itraconazole Sporanox, Tolsura , ketoconazole Extina, Ketozole, others and ritonavir Norvir. Follow-up support: Make sure you can get the help you need if questions or concerns arise after ordering. Shipping: Discreet, fast shipping is a must. All PDE5 inhibitors, including Viagra and Cialis, require a valid prescription regardless of the pharmacy or provider.Generic Viagra (sildenafil): Starting at $24/month; Generic Cialis (tadalafil): Starting at $39/month; Generic Cialis Daily (tadalafil): Starting at $89/month; Branded Viagra: . You should also avoid products you can buy online without a prescription that claim either to be generic forms of sildenafil or to contain sildenafil. (Sildenafil is the active drug in . By Ginger Skinner Last updated: June 14, If you’re looking for a less costly Viagra, you might want to ask your doctor about sildenafil. It’s the active ingredient in both .