Store mixed oral liquid in the refrigerator. The patients in studies had varying degrees of ED. There are many safe, reliable online services offering ED prescriptions. Children—Use is not recommended. If you experience a sudden loss of vision in one or both eyes, contact your doctor immediately. However, some states require a live video consultation.Examples of Viagra’s more commonly reported side effects include: headache. flushing (temporary warmth, redness, or deepening of skin color) stuffy nose. indigestion (upset stomach) mild vision. 15 minutes before sex for mg and mg, 30 minutes before sex for 50 mg: How long does it work? 4 hours: Generic Viagra (sildenafil) Cialis Daily Generic Cialis (tadalafil) Generic Cialis. Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a prescription drug that’s used in adult males* with ED. With ED, you.