This medicine usually begins to work for erectile dysfunction within 30 minutes after taking it. This medicine is available only with your doctor’s prescription. Dosing The dose of this medicine will be different for different patients. Do not use more of it and do not use it more often than your doctor ordered. 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. Sildenafil is also used in both men and women to treat the symptoms of pulmonary arterial hypertension.VIAGRA is available by prescription only in 25 mg, 50 mg, and mg tablets. Patients should always ask their doctors for medical advice about adverse events. You are . The normal dose when starting Viagra is 50 mg, as needed. The maximum dose of Viagra is mg each day. Doses above the maximum dose, such as mg .  · For oral dosage form (tablets): Adults up to 65 years of age—50 milligrams (mg) as a single dose no more than once a day, 1 hour before sexual intercourse. .