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What is Hydroxyurea?

Hydroxyurea (common brand name hydrea) is commonly seen in hematology

Chances are you will see it being used in your hematology clinical rotations. The reason why it is used is primary linked to the fact that it has marrow suppressive effects. So if someone presents with a myeloproliferative disorder such as essential thrombocytosis (too many platelets) or polycythemia, hydroxyurea is commonly used because it helps to suppress the marrow and curb over-proliferation of RBCs and platelets.

However, another not as intuitive use of hydroxyurea is also in the context of sickle cell disease. Hydroxyurea is often used to increase the concentration of fetal hemoglobin. In individuals who have sickle cell disease, they predominantly have a form of hemoglobin known as Hb S, along with a variable amount of fetal hemoglobin Hb F (read this article to learn more about fetal hemoglobin).

So why do we care that hydroxyurea can increase the levels of Hb F?

Well it turns out that it is an inhibitor of the polymerization that occurs in RBCs that cause them to become sickled, so the severity of the disease is actually related to the concentration of Hb F. Needless to say, hydroxyurea is a game changer for patients with sickle cell disease.

Anyways to summarize, 3 common hematological reasons for which hydroxyurea is used include:

  1. Essential thrombosis because of its marrow suppressive effects
  2. Polycythemia because of its marrow suppressive effects
  3. Sickle cell disease because it increases production of fetal hemoglobin