The information provided is for educational purposes only and is not intended to replace discussions with a healthcare provider. Sildenafil for pulmonary hypertension can also be known by the brand names Revatio and Grandipam. Such patients must not apply any out-of-pocket expenses incurred using this Savings Offer toward any government insurance benefit out-of-pocket spending calculations, such as Medicare Part D true out-of-pocket TrOOP costs You are responsible for reporting use of this Savings Offer to any private insurer, health plan, or other third party who pays for or reimburses any part of the prescription filled using this Savings Offer, as may be required. Key facts It usually takes 30 to 60 minutes for sildenafil to work for erectile dysfunction. Please expect up to 4 to 6 weeks for reimbursement.About sildenafil (Viagra) Sildenafil is a medicine used to treat erection problems (erectile dysfunction). Sildenafil is also sometimes used to treat pulmonary hypertension (high blood pressure in the blood vessels that supply the lungs). If you have erection problems sildenafil works by temporarily increasing blood flow to your penis when. Cialis lasts up to 36 hours in the body, while Viagra lasts 4–6 hours in the body. Both are taken 30 minutes before sex. Cialis can cause limb pain, while Viagra can cause vision change, rash. If you have these symptoms, stop taking VIAGRA and contact a doctor right away. have or have had heart problems such as a heart attack, irregular heartbeat, angina, chest pain, narrowing of the aortic valve, or heart failure. have low blood pressure, or high blood pressure that is not controlled.