Hydroxyurea in the Treatment: Adverse Reactions

In: Disease

3 Jun 2010

Adverse ReactionsIn the study, the most commonly occurring adverse reactions were hema-tologic, including neutropenia, and low reticulocyte and platelet levels, which necessitated temporary cessation of therapy in almost all patients. Hemato-logic recovery usually occurred within two weeks. Other nonhematologic effects included skin rash, hair loss, fever, weight gain, gastrointestinal disturbances, bleeding, and parvovirus B-19 infection.

The nonhematologic events occurred with similar frequencies in the hydroxy-urea and placebo treatment groups. Melanonychia has also been reported in patients receiving hydroxyurea for sickle cell anemia.
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Contraindications and Precautions

Hydroxyurea is contraindicated in patients with a previous hypersensitivity to it or to any other components of its formation. Hydroxyurea therapy should be closely supervised, because some patients who received the recommended dose—15 mg/kg/day—have experienced severe myelosuppression, requiring interruption of treatment and dose reduction.

Kidney and liver function, as well as hematological status, should be assessed before treatment is begun, and these tests should be repeated during treatment. Interruptions of therapy are recommended when:

  • neutrophil levels are below 2,000/mm3.
  • platelet counts are below 80,000/mm3.
  • hemoglobin levels fall below 4.5 g/dl.
  • reticulocyte counts are below 320,000/mm3.
  • reticulocyte counts fall below 80,000/mm3 and hemoglobin concentrations are below 9 g/dl.

Although hydroxyurea has not been indicated for patients with human immunodeficiency virus (HIV) infection, if HIV-infected patients are receiving this agent and, in particular (Bristol-Myers Squibb Immunology) and/or (Bristol-Myers Squibb Immunology), close monitoring for signs and symptoms of pancreatitis and hepatotoxicity is recommended. If signs and symptoms of pancreatitis or hepato-toxicity develop, patients should permanently discontinue hydroxyurea therapy.

Studies are now under way to test the safety and effectiveness of hydroxyurea in children.

Pregnancy and Lactation

Hydroxyurea is a potent teratogen in a wide variety of animal models, and it may cause fetal harm when administered to pregnant women. It is embryotoxic and causes fetal malformations at a dosage of 180 mg/kg per day (about 0.8 times the maximum recommended human daily dose on a milligram-per-squared-meter [mg/m2] basis) in rats and at 30 mg/kg per day (about 0.3 times the maximum recommended human daily dose on an mg/m2 basis) in rabbits. Decreased fetal viability, reduced live litter sizes, and developmental delays were characteristic of embryotoxicity.

Because hydroxyurea is excreted in human milk, nursing mothers need to decide whether to discontinue nursing or to discontinue the drug because of the potential for serious adverse reactions.


Sickle cell disease is the most common genetic disease in the U.S. As a result of increasing educational efforts being made in public health, the number of new cases in the U.S. should decline in the years ahead.

Unfortunately, no cure is yet available; treatment usually focuses on alleviating symptoms. Hydroxyurea can significantly prevent associated complications, but it is approved only for patients over age 18 who have had at least three painful crises in the previous year. Patients should be carefully monitored for hematologic adverse reactions.

Because of the teratogenic effects of hydroxyurea, mothers who are breastfeeding should either discontinue nursing or discontinue the drug therapy. Studies are being conducted to gain approval for to be used in patients younger than age 18. As our understanding of sickle cell disease and various treatments used to combat painful crises increases, it is hoped that better pain management and a possible cure might be realized.

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