If we combine this information with your protected health information, we will treat all of that information as protected health information and will only use or disclose that information as set forth in our notice of privacy practices. When hypertension occurs in the lungs, the heart must work harder to pump enough blood through the lungs. Generic versions of sildenafil, vardenafil and tadalafil are available. When oral medications might not be safe Check with your health care team before you take any medicine for erectile dysfunction. These medicines prevent an enzyme called phosphodiesterase type-5 from working too quickly. Oral medicine for ED also might not be safe or work well if you have: Very low blood pressure, called hypotension, or uncontrolled high blood pressure, called hypertension. Without physical action to the penis, such as that occurring during sexual intercourse, sildenafil will not work to cause an erection.Generic version. Viagra is available in generic form called sildenafil. A generic drug is an exact copy of the active drug in a brand-name medication. Sildenafil oral tablet is available as a brand-name drug and as a generic drug. Brand names: Viagra, Revatio. Sildenafil comes in three forms: an oral tablet, an oral . 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 alcohol. Its effects .