Most companies have an FAQ or shipping policy page you can reference to learn whether discreet packaging is available. Most erectile dysfunction medications belong to the drug class known as PDE5 inhibitors , which help relax the muscles and increase blood flow to allow for a full erection. Pfizer Canada Inc. What Are the Symptoms of Erectile Dysfunction? Payment options: Consider how you’d like to pay.Learn more about sildenafil oral. 1 Sildenafil is used to treat high blood pressure in the lungs (pulmonary hypertension). Learn more about Revatio.1 This is a generic drug. . Drug details Here are some details on sildenafil: Drug class: phosphodiesterase type 5 (PDE5) inhibitor Drug forms: oral tablet, liquid suspension, intravenous (IV) bolus . Viagra dosage for erectile dysfunction (ED) is usually milligrams (mg), but those over 65 may start at 25 mg. Your doctor will also need to consider possible drug interactions.