This medicine usually begins to work for erectile dysfunction within 30 minutes after taking it. In females, sildenafil may also increase blood flow to the genitals. To use the oral liquid: Shake the bottle well for at least 10 seconds before each use. Viagra has been shown not to affect libido in men, and its mechanism as a vasodilator medication that widens the blood vessels does not seem to lend itself to treating desire disorders. Read and follow these instructions carefully before you start using sildenafil and each time you get a refill of your medicine. Adverse Effects Warnings and Precautions Sildenafil has systemic vasodilatory effects and, as such, should be prescribed with caution to patients who may be sensitive to such blood pressure changes, such as patients with left ventricular outflow obstruction and impaired autonomic control of blood pressure.Generic Viagra (sildenafil) is an alternative to the branded Viagra drug that can be used for treating erectile dysfunction (ED). It’s now sold by many manufacturers, including online. The Savings Offer and Program expire on 12/31/ For further information, call , visit test1.ru, or write: Viatris Inc., P.O. Box , Mission, KS See risks & benefits. Learn more about what VIAGRA® (sildenafil citrate), a prescription treatment for ED. 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. For sildenafil to work properly, you’ll need to be sexually excited.