NIH Research Matters
May 23, 2011
Common Sickle Cell Treatment Safe for Babies
A medication used to treat sickle cell disease in adults also appears to be safe and effective for children as young as 8 months, a new study reports. The drug hydroxyurea led to fewer painful episodes and improved blood counts in treated babies.
Sickle cell disease is an inherited blood disorder that affects more than 70,000 Americans, mostly of African descent. It causes severe pain, organ damage and sometimes early death. The condition arises from a genetic defect that alters the structure of hemoglobin, the oxygen-carrying protein found in red blood cells. The modified hemoglobin causes normally round red blood cells to become stiff, sticky and sickle-shaped. The deformed cells can block blood vessels and rob tissues of needed blood and oxygen.
In 1995, a major NIH-funded clinical trial showed that hydroxyurea could reduce the number of pain crises and related hospitalizations by about half in adults with sickle cell disease. The drug works by boosting blood levels of fetal hemoglobin, a type of hemoglobin produced before and shortly after birth. It nearly disappears from the bloodstream as production of adult hemoglobin takes over. Fetal hemoglobin reduces the tendency of sickle hemoglobin to deform red blood cells.
To see if hydroxyurea might lead to similar benefits in very young children, Dr. Winfred C. Wang of the St. Jude Children's Research Hospital in Memphis led a multisite clinical trial that enrolled 193 children with sickle cell disease. Primary funding came from NIH’s National Heart, Lung and Blood Institute (NHLBI).
Children ages 8 to 19 months were randomly divided into 2 groups. One received daily doses of liquid hydroxyurea for up to 2 years. The other received a look-alike placebo. The children were examined at least once a month to evaluate several measures of health. The results were reported in the Lancet on May 14, 2011.
The main clinical tests—scans of the spleen and assessment of kidney filtering capacity—found no significant differences between the hydroxyurea and placebo groups. However, children in the treatment group showed improvements in other tests of spleen and kidney function. Hydroxyurea also reduced the occurrence of pain episodes. The treatment group had half as many pain events—177 events among 62 participants, compared to 375 events among 75 participants in the placebo group.
Hydroxyurea also reduced the risk of a painful swelling of the hands or feet known as dictylitis. Treated children needed fewer hospitalizations and blood transfusions and had fewer episodes of a pneumonia-like complication called acute chest syndrome. As in adults, children taking hydroxyurea had elevated levels of fetal hemoglobin compared to children receiving a placebo.
Although the primary spleen and kidney tests found no differences between the 2 groups, improvements may arise over time, the scientists say. They plan to continue following the children through 2016 to look at the long-term effects of treatment.
"There are now strong reasons for health care professionals to consider starting children who have sickle cell disease as early as possible on hydroxyurea," says NHLBI Acting Director Dr. Susan B. Shurin. "Less pain and fewer hospital stays are obvious improvements in the quality of life for the youngest children born with this condition."
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