Vardenafil usually works for 4 to 5 hours. As with sildenafil, a high-fat meal or alcohol keep the body from absorbing it as quickly. This is thanks to Viagra being the first solution widely available for assisting men with ED — not to mention its clever marketing over the years. For the treatment of ED, both Sildenafil and Viagra are produced in 25mg, 50mg and mg pills. Call your doctor right away if you have blurred vision, confusion, dizziness, faintness, or lightheadedness when getting up from a lying or sitting position suddenly, sweating, or unusual tiredness or weakness.Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes . 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 . SILDENAFIL (sil DEN a fil) treats erectile dysfunction (ED). It works by increasing blood flow to the penis, which helps to maintain an erection. This medicine may be used for .