If you experience a sudden loss of vision in one or both eyes, contact your doctor immediately. Children 1 year of age and older weighing 20 kg or less—10 mg 3 times a day. Do not keep outdated medicine or medicine no longer needed. However, the dose is usually not more than 80 mg 3 times a day. Sildenafil usually should not be taken more than once every 24 hours. Brand names Why is this medication prescribed?Refill and transfer prescriptions online or find a CVS Pharmacy near you. Shop online, see ExtraCare deals, find MinuteClinic locations and more.  · The effects may be increased because of slower removal of the medicine from the body. Leukemia (blood related cancer) or. Multiple myeloma (blood related cancer) or. Sickle-cell anemia (blood disorder)—Sildenafil should be used with caution in these patients as problems with prolonged erection of the penis may occur.  · The cost of sildenafil without insurance starts at $* for a quantity of 30, 20mg tablets, using a RxSaver coupon. The cost of sildenafil can vary in price depending on the pharmacy your sildenafil prescription is filled at. Below is a list of pharmacies and the starting cost of a sildenafil prescription using an RxSaver coupon.