Slowly pull back the plunger until the required dose. For treatment of pulmonary arterial hypertension: For oral dosage forms suspension or tablets : Adults—20 milligrams mg 3 times a day. If you have any questions or concerns, please talk to your doctor. From Mayo Clinic to your inbox Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. However, the dose is usually not more than 80 mg 3 times a day. If you see air bubbles in the syringe, repeat the steps.Why it’s used Sildenafil oral tablet is used to treat ED and PAH. Generic oral tablets are available for both conditions, but the brand-name drugs each treat only . 20 to 25mg Sildenafil. 25mg is the minimum dosage of sildenafil approved to treat erectile dysfunction. You might be prescribed sildenafil at this dosage if you . Sildenafil is designed to be taken at a minimum dose, and taking too much of it will increase your risk of experiencing side effects, particularly more dangerous .