If you often forget doses, it may help to set an alarm to remind you. Children 1 year of age and older weighing 20 kg or less—10 mg 3 times a day. However, if you take sildenafil with a high-fat meal, it will take longer for the medication to start to work. To provide you with the most relevant and helpful information, and understand which information is beneficial, we may combine your email and site usage information with other information we have about you. The major circulating metabolite results from N-desmethylation of sildenafil, and is itself further metabolized.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. 1 day ago · Cost: If the price for branded Viagra is outside of your budget, Lemonaid’s $2 sildenafil pills are some of the lowest priced Viagra alternatives that we’ve found. Product details Usage: take.  · Drug information provided by: Viagra; Descriptions. Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase 5 (PDE5) inhibitors. Adults up to 65 years of age—50 milligrams (mg) as a single dose no more than once a day, 1 hour.