People with heart conditions should never take ED medications without consulting a doctor. An evaluation of visual function at doses up to twice the maximum recommended dose revealed no effects of VIAGRA on visual acuity, intraocular pressure, or pupillometry. Men with untreated ED had relatively low baseline scores for all aspects of sexual function measured again using a 5-point scale in the IIEF. Follow your doctor’s orders or the directions on the label. Do not press on the plunger of the syringe.What is Sildenafil (Viagra)? Drug Facts Common Brands Viagra Drug Class PDE-5 inhibitor Controlled Substance Classification Not a controlled medication Generic Status Lower-cost generic available Availability Prescription only How Sildenafil (Viagra) works Sildenafil (Viagra) is a phosphodiesterase-5 (PDE-5) inhibitor.  · For treatment of erectile dysfunction: For oral dosage form (tablets): Adults up to 65 years of age—50 milligrams (mg) as a single dose no more than once a day, 1 hour before sexual intercourse. Alternatively, the medicine may be taken 30 minutes to 4 hours before sexual intercourse. Your doctor may adjust your dose if needed. GoodRx can help you save over 80% off the average retail price of the generic versions. Generic sildenafil at certain pharmacies is as low as $ with a free GoodRx discount. You can also find generic tadalafil and vardenafil for as low as $ and $ , respectively. What’s more, you can find brand-name Stendra for as low as .