What is your opinion on hydroxyurea in elementary age children with Sickle Cell SD?


Hydroxyurea has been used medically in the United States since 1967 when it was approved by the FDA for some types of cancer.  The side effects are well known due to use as an antineoplastic medication.  Although other medications are known increase fetal hemoglobin hydroxyurea was chosen to be studied in sickle cell disease due to the fact that it is an oral medication and has been used for decades and has mild side effects that are reversible when the medication is stopped.  The dosages that cause toxicity are well known.


In 1984 the first study of this medication to treat sickle cell disease was initiated.  It was given to adults with sickle cell disease as a double-blind, placebo controlled trial (some patients were given hydroxyurea and some were given a pill that did not contain hydroxyurea, neither the patients nor the doctors knew who was getting the hydroxyurea).  At the end of the study it was shown that hydroxyurea decreased episodes of acute chest syndrome and pain by about 50% in the hydroxyurea arm.  These patients continue to be studied for side effects and benefit.  In the most recent publication it was reported that even people who stopped taking hydroxyurea or were taking it intermittently had increased survival compared to people who had never taken hydroxyurea.  Though there is the possibility of cancer being caused by hydroxyurea it has not been seen in this or other large studies of hydroxyurea for other diseases. Either hydroxyurea does not cause cancer in the doses given or the incidence is so low that it cannot be detected at these doses in the studies that have been done.  In animal studies where very high doses have been given toxicity has been seen, but these are doses never given in medical practice.


What about children?  The reason the FDA has not approved hydroxyurea for use in children is there has never been a study like the adult study to show that it is effective in a double blind study.  Why?  Hydroxyurea is effective and doctors feel it would be unethical to do such a study just to prove a known fact.  All the studies in children have been to determine safety for use in children.  The youngest children to receive hydroxyurea have been about two and a half years old.  Hydroxyurea has not been found to have any negative side effects or different side effects than those seen in adults.  It is considered safe when given to children at the doses currently used to treat sickle cell disease and the children are monitored by a physician familiar with the use of this medication, usually a hematologist.


I think hydroxyurea is safe and effective for children, even young children.  There is controversy, for me, as to the dose given.  I have always felt that this is a medication that will be given for the lifetime of the child and the lowest effective dose is the best dose, not the Maximum Tolerated Dose (MTD), with an exception.  This dose is usually about 25 mg/kg/day.  The maximum dose is considered to be 35 mg/kg/day.  I have seen good results with a low incidence of side effects at the lower dose.  There is a study in another country (India) were doses of 10 mg/kg/day were seen as effective in reducing symptoms of sickle cell disease.


What about a recent study that showed you could stop transfusions for stroke risk (abnormal TCD) in some children (TwITCH Study) and use hydroxyurea to decrease stroke risk?  In this case, since the risk benefit favors using a higher dose of hydroxyurea, I would use the MTD for this indication.


The effect of hydroxyurea is greater than just increasing fetal hemoglobin, it is too much to give this information here.  You can ask your healthcare provider for that information.


BOTTOM LINE: Hydroxyurea is a safe, effective, and an underutilized medication in sickle cell disease.  Always look at the risk-benefit of medications and treatments in medicine.  The risk of hydroxyurea is low, the benefit is high.  This is a decision to be made with your healthcare provider.  Hydroxyurea must be monitored on a regular basis, your healthcare provider must be familiar with the use of this medication in children.



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