Sickle Cell Anemia and Hydroxyurea

Normal red blood cell and sickle cell
Normal red blood cell and sickle cell. SCIEPRO/Science Photo/Library/Getty Images

In sickle cell anemia, currently the best medication we have to prevent complications is called hydroxyurea, sometimes abbreviated HU.  Hydroxyurea was first developed as a chemotherapy medication in the 1960s.  It was used for a wide variety of malignant conditions initially, but it has been used in sickle cell disease now for more than 25 years.   Hydroxyurea is the only FDA (Food and Drug Administration) approved medication to treat sickle cell anemia.

 

How Does Hydroxyurea Work in Sickle Cell Anemia?

In sickle cell anemia, hydroxyurea helps the body produce more fetal hemoglobin (Hb F). This is a hemoglobin found in newborn babies. Newborn babies with sickle cell disease do not have complications in the first few months of life because fetal hemoglobin prevents the red blood cell from sickling. This increase in fetal hemoglobin, helps keep your red blood cell round instead of sickled. These round red blood cells are able to flow through blood vessels smoothly.

What Are the Benefits of Hydroxyurea Therapy?

In numerous studies in both children and adults with sickle cell anemia, hydroxyurea treatment has been associated with fewer painful crises, fewer acute chest syndrome (lung complication) events, reduction in the need for transfusion, and reduction in the need for hospitalization. Hydroxyurea also  increases your hemoglobin, making you less anemic.

Additionally, hydroxyurea therapy has been associated with longer life expectancy in adults with sickle cell anemia.

What Are the Side Effects of Hydroxyurea Therapy?

Based on the doses used in sickle cell anemia, the side effects are relatively mild. Hair loss, mouth sores, and increased risk of infection associated with chemotherapy are rarely seen.

Hydroxyurea can decrease white blood cells, hemoglobin, and platelets. Because of this side effect, your physician will monitor your counts closely with complete blood count and reticulocyte count. Occasionally, abdominal pain is seen but this is usually mild and resolves without intervention. Another side effect is darkening of the nails called melanonichyia. In general, most patients are able to find a dose of hydroxyurea they can tolerate with few side effects.

What Patients Should Consider Treatment With Hydroxyurea?

According to the most recent sickle cell management guidelines from the National Heart, Lung, and Blood Institute (part of the National Institutes of Health) published in 2014, all children with hemoglobin SS and sickle beta zero thalassemia should be offered hydroxyurea therapy to prevent complications after 9 months of age. In adults hydroxyurea therapy should be considered for patients who have 3 or more painful crises per year, pain that interferes with daily activities, a history of acute chest syndrome,  or severe anemia that interferes with daily activities.

Does Hydroxyurea Cause Cancer?

Historically, this has been a huge concern. The patients initially treated with hydroxyurea had conditions that increased their risk of malignancy (cancer) but because they developed cancer while on hydroxurea therapy it was attributed to the medication. In sickle cell disease, the answer is no.  According to a study published in 2014 looking specifically at patients with sickle cell disease, those that took hydroxyurea were not at increased risk of cancer compared to those who did not take hydroxyurea.

Can I Take Hydroxyurea During Pregnancy?

At this time it is not recommended to take hydroxyurea during pregnancy. Hydroxyurea is a class D medication indicating there appear to be risk to developing fetus. There are a small number of cases reporting normal pregnancies in women with sickle cell disease who continued hydroxyurea but additional information is needed.

Can I Ever Stop Taking Hydroxyurea?

No, hydroxyurea is not a cure. It only works if you take it as directed. Hydroxyurea is a chronic medication for a chronic disease similarly to medications persons with high blood pressure take everyday.

Sources:

Ware RE. How I use hydroxyurea to treat very young patients. Blood. 2010;115(26):5300-5311.

Castro O, Nouraie M, Oneal P. Hydroxycarbamide treatment in sickle cell disease: estimates of possible leukaemia risk and of hospitalization survival benefit. British Journal of Haematology. 2014;167:687-691. 

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