You can buy it from a store-based pharmacy or reputable online pharmacy with a prescription. These medicines prevent an enzyme called phosphodiesterase type-5 from working too quickly. Talk to your doctor about eating grapefruit and drinking grapefruit juice while taking this medicine. What should I do if I forget a dose? Most adults and children aged 1 year and over can take sildenafil for pulmonary hypertension. By controlling the enzyme, sildenafil helps to maintain an erection after the penis is stroked. If you are taking sildenafil to treat PAH, you will probably take sildenafil three times a day with or without food.Sildenafil (Viagra, Revatio) is a moderately priced drug used to treat erection problems in men. It is also used to treat pulmonary arterial hypertension, a serious heart and lung drug is more popular than comparable drugs. It is available in generic and brand versions. Generic sildenafil is covered by most Medicare and insurance plans, but . Viagra comes as an oral tablet in different dosages. Discuss with your doctor what’s an appropriate dose for you. For daily use, Goldstein said, the generic form, sildenafil, comes in mg tablets. Stick to the Indian version of Viagra, sold in Vietnam as Kamagra,as good as the original, I know dozens of people who have been using it for years with “success” and without any health effects, sold in HCM for $ a tely no reason to bring your grossly overpriced foreign Viagra in,unless of course you want to add even further to the assets .