The four main medicines taken by mouth for erectile dysfunction are: Avanafil Stendra. Medicines that you take by mouth are called oral medicines. Your doctor may need to change the doses of your medications or monitor you carefully for side effects. However, it stays in your body for up to 36 hours and can be taken every 24 hours, so it can work for you constantly. You should only be treated with one of these products at a time. · Learn about the dosage of Viagra for erectile dysfunction (ED). you may have a lower starting dosage than usual if you’re over age For example, a year-old might start at a dose of 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 . Side Effects. Dizziness, headache, flushing, or stomach upset may occur. Vision changes such as increased sensitivity to light, blurred vision, or trouble telling blue and green colors apart may.