You’ll also need to fill out a medical questionnaire with answers about your medical history, current medications, and lifestyle habits. Always keep medications out of reach of children and pets. Sildenafil may cause side effects. Oral medicines for ED usually work well and cause few side effects. Erectile dysfunction is a condition where the penis does not harden and expand when a man is sexually excited, or when he cannot keep an erection. Your doctor may adjust your dose as needed and tolerated.A newer form of the medicine that dissolves on the tongue might work faster than the pill that you swallow. Tadalafil (Cialis). This medication is taken with or without food an hour before sex. It works for up to 36 hours. such as cost, ease of use, how long the drug’s effects last and side effects. Generic versions of sildenafil. Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the . 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% .