If you are a Mayo Clinic patient, this could include protected health information. Mean sildenafil plasma concentrations measured after the administration of a single oral dose of mg to healthy male volunteers is depicted below: Figure 5: Mean Sildenafil Plasma Concentrations in Healthy Male Volunteers. Viagra is also informally known as “vitamin V”, “the blue pill”, or “blue diamond”, as well as various other nicknames. Do not use this medicine if you are also using a nitrate medicine, often used to treat angina or high blood pressure. Your doctor may adjust your dose if needed. Sildenafil works on the PDE5 enzyme in the lungs to relax the blood vessels. Without physical action to the penis, such as that occurring during sexual intercourse, sildenafil will not work to cause an erection.AdWith RexMD you’re saving time and money with our Viagra delivery. Get started now. Reliable E.D. meds prescribed by real doctors. Get your free & private online visit today10K+ visitors in the past monthFree Shipping · Discreet Packaging · Real Doctors · Personalized PlanTypes: Sertraline · Erectile Dysfunction · Testosterone · Genital Herpes. The list below does not include all possible drug interactions with Sildenafil (Viagra). Please note that only the generic name of each medication is listed below. More on Sildenafil (Viagra) interactions. Cialis is a brand-name medication used to treat erectile dysfunction. You can look into a generic form and other ways to save money. Viagra is a brand-name medication that contains the active drug sildenafil. This active drug comes as a generic medication, too. Sildenafil and brand-name Viagra are both used to treat ED.