However, if you take sildenafil with a high-fat meal, it will take longer for the medication to start to work. Kidney disease, severe or Liver disease, severe—Use with caution. Sildenafil usually should not be taken more than once every 24 hours. If too much is used, the chance of side effects is increased. Benjamin P.Sildenafil is a medication used in the management and treatment of erectile dysfunction and pulmonary arterial hypertension. It is in the phosphodiesterase-5 inhibitor (PDE5-I) class of medications. This activity describes the indications, actions, adverse effects, and contraindications of sildenafil as an agent in the clinical setting. Knowledge . Viagra comes as an oral tablet in different dosages. Discuss with your doctor what’s an appropriate dose for you. For daily use, Goldstein said, the generic form, sildenafil, comes in mg tablets. 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 .