Before using this drug, patient should disclose to the physician the medical history, including any allergies (especially drug allergies), any penis conditions such as fibrosis/scarring, history of painful/prolonged erection (priapism), sickle cell anemia, blood system cancers (such as leukemia or myeloma), or Peyronie's disease, eye problems (retina diseases). kidney or liver disease, bleeding disorders or active stomach ulcers, heart diseases, stroke or severe high or low blood pressure. Limit alcohol intake, as it may aggravate side effects of this drug.