Some men prefer Viagra over the Sildenafil generic. Place the tip of the syringe into you or your child’s mouth and point it towards the cheek. Do not keep outdated medicine or medicine no longer needed. If your dose is different, do not change it unless your doctor tells you to do so. Storage Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. It continues to work for up to 4 hours, although its action is usually less after 2 hours. If you see air bubbles in the syringe, repeat the steps.Sildenafil (Viagra) is a phosphodiesterase-5 (PDE-5) inhibitor. PDE-5 is a protein in your body that breaks down the molecules that normally cause an erection. . COMMON BRAND NAME (S): Viagra. USES: Sildenafil is used to treat male sexual function problems (impotence or erectile dysfunction-ED). In combination with sexual . Generic sildenafil is covered by most Medicare and insurance plans, but some pharmacy coupons or cash prices may be lower. Get sildenafil for as low as $, which is 95% off the average retail price of $ for the most common version, by .