It is important to tell your doctor about any heart problems you have now or may have had in the past. Keep from freezing. Take sildenafil as needed before sexual activity. Tell your doctor if any of these symptoms are severe or do not go away: headache. These medicines are called PDE5 inhibitors. Store mixed oral liquid in the refrigerator.This means that 4 hours after you take a dose, your body has cleared half of the dose. In most cases, it takes about 5 half-lives for your body to completely remove a drug from your system. So. According to price-comparison site test1.ru, generic Revatio will cost you as little as $ per pill, depending on where you fill your prescription. That’s compared with . Sildenafil is a generic drug, which is an exact copy of the active drug in a brand-name medication. The generic is considered to be as safe and effective as the original drug. And generics tend to.