It may be difficult to remain firm despite wanting to have sex. Follow the manufacturer’s directions to use and clean the oral syringe. Your doctor will tell you not to take sildenafil if you are taking street drugs containing nitrates. Generic vs. If you prefer, you may contact the U.If you’re looking for a less costly Viagra, you might want to ask your doctor about sildenafil. It’s the active ingredient in both branded Viagra and the drug Revatio, which is a lower . Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial . You can only get VIAGRA by prescription from your doctor or healthcare provider. HOW TO GET BRAND-NAME VIAGRA top. Pay for your VIAGRA prescription and mail .