Hi Nicole,
Hydroxyurea use is an ongoing therapy. It will only work while it is being used. Although it is used with cancer patients, it is not what one would think of as a chemo drug. It is used because it suppresses the bone marrow, which helps deprive cancer cells of a good blood source. This is used in combination with other drugs which are truly chemotherapy drugs. For this same suppression of the bone marrow reason, it is useful in thalassemia. Blood transfusions also serve this purpose in thal, as the higher the hemoglobin, the less bone marrow activity takes place, which is one of the goals of transfusion. In addition to raising the Hb so that there is a sufficient supply of oxygen, transfusion suppresses the bone marrow so fewer defective red blood cells are produced. The defective red blood cells and unmatched alpha globin chains that are produced by thals create many problems for thals and limiting their production is always a goal in thalassemia. In some patients like Manal's son, there hasn't been any real rise in Hb through hydroxyurea use, but his Hb has stayed fairly level, and his health remains far better than one might expect with the Hb level he normally maintains (Usually around 7). The hydroxyurea is suppressing his bone marrow so red cell production is not overstimulated by the low Hb and his blood remains healthy, leading to a healthy active child who is doing remarkably well in spite of his low Hb level. Avoiding or reducing transfusions is a top goal in thalassemia because taking blood does create problems and the less blood needed, the better it is for the patient.
Hydroxyurea has been shown to be safe at very young ages. There is a full report of the study using hydroxyurea in sickle cell patients at
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1895275/ I will quote one relevant bit from the text. The age of the children involved was 2.6 to 4.4 years.
We believe hydroxyurea is a relatively safe drug for children with SCA but requires periodic monitoring of blood counts and physical examinations. As with any new treatment, hydroxyurea therapy needs to be closely monitored for toxicity, which may prove difficult in developing countries.
Hydroxyurea should be used for at least one and hopefully, two years before making an assessment of its full value. Its effect has been shown to continue to increase into the third year of use and beyond. I will also point out that the next generation of hemoglobin inducing drugs is already in trials, and unofficially, results have looked good so far, far surpassing hydroxyurea in ability to raise the hemoglobin level. I also want to mention that it is not easy to predict how much this drug will help. It has been noted that patients with certain mutations in beta thalassemia have seen better results, so the actual gene defect also has some bearing on the results.