Hydroxyurea Effective With Few Side Effects in the Sickest Sickle Cell Patients

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Dec. 9, 1999 (Atlanta) -- Hydroxyurea, a drug approved for use in sickle cell anemia, improves the function of red blood cells for up to six to seven years with few negative side effects, according to a study presented at the 41st Annual Meeting of the American Society of Hematology in New Orleans. The drug may reduce death rates in adults with moderate to severe sickle cell anemia. Hydroxyurea is the only known therapy to prevent sickle cell crisis and decrease the pain attacks and pneumonialike episodes.

"The main conclusion is that there is no unexpected toxicity of the hydroxyurea," lead author Martin H. Steinberg, MD, tells WebMD. "We haven't yet seen patients develop cancer or leukemia or have unexpected side effects. The second [conclusion] is that the data suggest ... that these patients who take hydroxyurea have reduced mortality compared to the patients who didn't take the drug. We're excited and encouraged by the news." Steinberg is associate chief of staff of research at the VA Medical Center and professor of medicine at the University of Mississippi, both in Jackson.

Sickle cell anemia is an inherited disorder of red blood cells that most often affects blacks. It causes red blood cells to be shaped abnormally, like a sickle. In this sickle shape, the red blood cells are fragile, are unable to carry oxygen, and can clog vessels. When the vessels become blocked, they cause severe pain and tissue damage. These episodes are called pain crises or vaso-occlusive events. Traditionally, pain crises are treated with blood transfusions, vigorous hydration, and pain medications.

There is no cure for sickle cell anemia but there are many new therapies and medications. Hydroxyurea is one drug that has been effective in reducing the frequency of pain crises and the need for blood transfusions in adults with sickle cell anemia.

In this study, almost 300 adults with moderate to severely symptomatic sickle cell anemia were randomly selected to receive treatment with maximum doses of hydroxyurea or placebo. After treatment was stopped, patients were followed for six to seven years. Of the patients who received hydroxyurea, there was improvement of the red blood cells ability to carry oxygen and less breakage of the cells. In the same group, about 14% died, whereas about 20% of those on placebo died. The most common cause of death was pulmonary disease. There was no significant increase risk of death for users of hydroxyurea.


"Perhaps the reason that hydroxyurea is reducing mortality is that it's preventing these vascular complications that are the chief acute problem of patients with sickle cell disease," says Steinberg. However, he notes that this study was not designed to assess why the drug works. Steinberg recommends that patients treated with hydroxyurea be followed closely.

"We selected the sickest patients [to study]," says Steinberg. "So I think it's very good news that, in the sickest group of patients, we appear to be extending their life. ... If it works this well in the very sickest people, perhaps it will work equally well, or possibly better, in people who are not so sick to begin with." Currently, the investigators are attempting to corroborate their findings by continuing the study with more patients over a longer period of time.

Vital Information:

  • Sickle cell anemia is an inherited blood disorder that causes red blood cells to form a sickle shape, leaving them fragile, unable to carry oxygen, and more prone to clogging blood vessels.
  • The drug hydroxyurea improves the ability of red blood cells to carry oxygen and decreases breakage of the cells among patients with moderate to severe sickle cell anemia.
  • Patients taking hydroxyurea experienced lower death rates, decreased pain attacks and fewer pneumonialike episodes.
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