Both men and women using hydroxyurea should use birth control to prevent pregnancy. The use of  hydroxyurea by either parent may cause birth defects.
Using hydroxyurea may increase your risk of developing other types of cancer, such as leukemia or skin cancer. Wear protective clothing and use sunscreen when you are outdoors.
Hydroxyurea can weaken your immune system. Call your doctor at once if you have a fever, chills, body aches, extreme tiredness, shortness of breath, bruising, or unusual bleeding.
Before taking this medicine
You should not use hydroxyurea if you are allergic to it.
Tell your doctor if you have ever had:
kidney disease (or if you are on dialysis);
liver disease;
a wound or ulcer on your leg;
HIV or AIDS (especially if you take antiviral medicine);
high levels of uric acid in your blood; or
treatment with an interferon, chemotherapy, or radiation.
Using hydroxyurea may increase your risk of developing other types cancer or leukemia. Talk with your doctor about your specific risk.
Hydroxyurea can harm an unborn baby. Both men and women using this medicine should use birth control to prevent pregnancy. The use of this medicine by either parent may cause birth defects.
If you are a woman, keep using birth control for at least 6 months after your last dose of hydroxyurea.
If you are a man, keep using birth control for at least 1 year after your last dose (6 months if you took Siklos).
Tell your doctor right away if a pregnancy occurs while either the mother or the father is using this medicine.
This medicine may affect fertility (ability to have children) in men. However, it is important to use birth control because hydroxyurea may harm the baby if a pregnancy does occur.
You should not breastfeed while you are taking hydroxyurea.
Older adults may be more sensitive to the effects of this medicine.
