It might work longer if you have mild to moderate erectile dysfunction. Sildenafil is in a class of medications called phosphodiesterase PDE inhibitors. Oral medicine for ED also might not be safe or work well if you have: Very low blood pressure, called hypotension, or uncontrolled high blood pressure, called hypertension. These small differences affect the way each medication works, such as how quickly it takes effect and wears off, and the possible side effects. Shake the liquid well for 10 seconds before each use to mix the medication evenly. Stop taking VIAGRA and call your healthcare provider right away if you have any sudden vision loss sudden hearing decrease or hearing loss.Viagra is approved for this use in males ages 18 years and older. Viagra contains the drug sildenafil. It belongs to a class of drugs called phosphodiesterase type 5 (PDE5) . There’s no specific age at which erectile dysfunction (ED) starts. But ED is much more likely after the age of Although you can’t change your age, you can take steps to improve your overall physical health and prevent weight gain, heart disease, and diabetes. Men who . Viagra dosage is not based on weight, but your age can affect your dosage. Specifically, you may have a lower starting dosage than usual if you’re over age For example, a .