The effects may be increased because of slower removal of the medicine from the body. Do not mix the liquid with other medications or add anything to flavor the medication. Ask your doctor if you have any questions. Do not use more of it and do not use it more often than your doctor ordered. If you ever need emergency medical treatment for a heart problem, the healthcare providers who treat you will need to know when you last took sildenafil.Sildenafil is used to treat erectile dysfunction (ED) and to reduce blood pressure in pulmonary arterial hypertension (PAH). It is taken when needed for ED and daily for PAH. A headache, stomach upsets, and flushing are the main side effects, and it should not be taken within 24 hours of a nitrate. 5. Tips.  · 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. Financial assistance Next steps What is sildenafil? Sildenafil is a generic prescription medication. The Food and Drug Administration (FDA) has approved it to .