You can buy it from a store-based pharmacy or reputable online pharmacy with a prescription. Rarely reported side effects include: an erection that will not go away priapism. Sildenafil for pulmonary hypertension can also be known by the brand names Revatio and Grandipam. If you buy sildenafil for erectile dysfunction, it can also be known by the brand names Viagra, Aronix, Liberize and Nipatra. Take sildenafil up to 4 hours before you want to have sex. Talk to your doctor if you take too much sildenafil and you’re worried about any of these side effects: headaches.Sildenafil tablets for erectile dysfunction come in different strengths ranging from 25mg to mg. The usual dose is 50mg, when you need it. Do not take it more than once a day. The dose can be increased to mg or decreased to 25mg depending on its effect. Take sildenafil up to 4 hours before you want to have sex. Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the . Viagra Connect is an erectile dysfunction treatment which can be bought without a prescription. Viagra Connect contains Sildenafil 50mg and is designed for men aged 18 .