The medication was developed by U. Sildenafil comes as a tablet and suspension liquid to take by mouth. Medicines that you take by mouth are called oral medicines. What special precautions should I follow? Tell your doctor if any of these symptoms are severe or do not go away: headache. No side effects were reported in sexual partners. Tell your doctor if sildenafil is not working well or if you are experiencing side effects.Last updated: June 14, 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. Viagra (sildenafil) is a brand-name prescription drug that’s used to treat erectile dysfunction (ED). Learn about side effects, warnings, dosage, and more. “Over-the-counter medications play a significant role in providing accessible and convenient treatment for a wide range of common health conditions—with erectile dysfunction being .