Pregnant Women: There are increased risks for stroke, heart failure, preterm delivery, and maternal and fetal death for pregnant women with untreated pulmonary arterial hypertension. If you take too much Taking too much sildenafil can cause unpleasant side effects. Leukemia blood related cancer or Multiple myeloma blood related cancer or Sickle-cell anemia blood disorder —Sildenafil should be used with caution in these patients as problems with prolonged erection of the penis may occur. It can be dangerous to take sildenafil if you also take medicines called nitrates often given for chest pain. Children 1 year of age and older weighing 45 kilograms kg or more—20 mg 3 times a day.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 . Get sildenafil for as low as $, which is 95% off the average retail price of $ for the most common version, by using a GoodRx coupon. Prices Medicare Drug Info Side Effects Images Sildenafil (Viagra, Revatio) is a moderately priced drug used to treat erection problems in men. Sildenafil is used to treat erectile dysfunction (ED) and to reduce blood pressure in pulmonary arterial hypertension (PAH). It is taken when needed for ED and daily for PAH. A headache, stomach upsets, and flushing are the main side effects, and it should not be taken within 24 hours of a nitrate. 5. Tips.