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Year : 2010  |  Volume : 42  |  Issue : 1  |  Page : 32--35

Effective control of sickle cell disease with hydroxyurea therapy

Harminder Singh, Navin Dulhani, Bithika Nel Kumar, Prabhakar Singh, Pawan Tiwari 
 Department of Pharmacology, Government Medical College, Jagdalpur, Chhattisgarh, India

Correspondence Address:
Harminder Singh
Department of Pharmacology, Government Medical College, Jagdalpur, Chhattisgarh


Objective : Hemoglobin F augmentation is another approach to treat sickle cell disease (SCD). This study evaluates the efficacy and impact of Hydroxyurea (HU) on fetal hemoglobin (HbF) and other hematological parameters, which result in decreasing the painful crisis and lower hospital admissions. Materials and Methods : A prospective study was carried out in the Department of Medicine, Government Medical College, Jagdalpur. Twenty-seven patients with SCD received HU at a mean dose of 22 mg/kg/d. The baseline results were analyzed and compared with the post treatment result, at the end of one year. Statistics : Student«SQ»s t-test was used to determine the level of significance. Results : Twenty-four patients completed a one-year period successfully; a significant increase was noted in the mean HbF%, from 12.83 to 19.17, and the mean corpuscular volume (MCV) from 82.57 to 89.87 Fl. The mean hospital admission (numbers) in the last one year decreased from 4.75 to 2.25 and the mean number of SCD crisis for the last one year decreased significantly from 3.63 to1.67. Conclusion : We found a significant reduction in hospital admissions, a reduction in the overall sickle cell crisis and an associated improvement in HbF% without any significant side effects in the patients with SCD, treated with HU.

How to cite this article:
Singh H, Dulhani N, Kumar BN, Singh P, Tiwari P. Effective control of sickle cell disease with hydroxyurea therapy.Indian J Pharmacol 2010;42:32-35

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Singh H, Dulhani N, Kumar BN, Singh P, Tiwari P. Effective control of sickle cell disease with hydroxyurea therapy. Indian J Pharmacol [serial online] 2010 [cited 2022 Dec 2 ];42:32-35
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More than 50 years ago Janet Watson recognized that the red cells of infants with sickle cell trait failed to sickle in vitro; she hypothesized that these observations were due to the elevated HbF levels in infant blood. HbF interfered with HbS polymerization and it was appreciated that enough HbF, if evenly distributed among sickle erythrocytes, might 'cure' the sickle cell disease. A search was launched for pharmacological agents that could reverse the switch from gama to beta globin chain synthesis. [1] Bone marrow transplantation (BMT) was the only curative therapy, but its use was often limited by the lack of an HLA-compatible healthy donor. Reactivation of fetal hemoglobin (HbF) synthesis may be an alternative approach; a number of trials are now being conducted to test this hypothesis. [2],[3]

Beta globin chains characterize HbF and sickle gama globin chains are present in HbS. The first 'hemoglobin switching' agent, a nucleoside analog 5-azacytidine, was postulated to increase HbF by inducing gene expression. The other drug, Hydroxyurea (HU), is the prototype known to promote HbF production indirectly by perturbing the maturation of erythroid precursors, is administered orally with a once-daily dosing, has no immediate adverse effects, and is generally effective for patients with sickle cell disease (SCD). [4],[5]

The multicenter Phase I / II safety trial of HU therapy for severely affected school-aged children with SCA (HUG KIDS) demonstrated significant increases in hemoglobin concentration, mean corpuscular volume, and the percentage of HbF. [6] Subsequently, HU has been shown to aid the growth and development of children with SCD and prevent stroke recurrence in children with previous cerebrovascular accidents. [7]

An open-label study of HU in 32 patients with SCD showed that HbF synthesis increased in most patients treated with doses of HU, which produced limited myelotoxicity. HbF responses were dose-related, and in some patients the levels were as high as 15 to 20%. Laboratory studies suggested that HbF levels of at least 15 to 20% might be required for a clinical benefit, but in a study of untreated patients, it appeared that any increase above 4% might be beneficial. [8],[9]

Clinical efficacy has also been proven; in a double-blinded, placebo-controlled, randomized trial, involving severely affected adults with SCD, HU significantly reduced the number of painful vaso-occlusive events, blood transfusions, episodes of acute chest syndrome, and hospitalizations. More recently, long-term HU use has been shown to decrease mortality in adults with SCD. [10] For pediatric patients, HU has a similar toxicity profile, with only mild, transient, and reversible myelosuppression. [11] For adult patients, hydroxyurea has dose-related hematological efficacy and an acceptable short-term toxicity profile. [12],[13]

Recent findings suggest that the induction of HbF by HU involves the activation of soluble guanylate cyclase by NO, and reduces the rates of vaso-occlusive crisis in patients with SCD and recent data suggest that HU treatment can generate nitric oxide (NO). Nitric oxide has been proposed as a novel therapy for sickle cell disease via a number of pathways. [14],[15]

In a backward State like Chhattisgarh where the prevalence is about 22% for the sickle cell trait and 2 - 3% for full-blown sickle cell disease, where blood is in short supply, blood banking facilities are primitive, and voluntary blood donation is not a common practice, management of this disease becomes difficult. [16] Owing to social and economic reasons, patients cannot maintain the ideal pre-transfusion hemoglobin of 9 to 10.5 g/dL. In such resource-restricted settings, HU becomes the best alternative. The main objective of our study therefore is to evaluate the efficacy and safety of HU in SCD patients.

 Materials and Methods

The study was conducted from March 2008 to March 2009, in the Department of Medicine with help from the Pharmacology Department, Government Medical College, Jagdalpur, Chhattisgarh, India. Twenty-seven subjects were included, after obtaining informed consent and approval from the Institutional Ethics Committee.

Inclusion and exclusion criteria

All patients who had homozygous SCD proven by Hb electrophoresis, with a history of severe, recurrent vaso-occlusive sickle cell pain that required three or more hospitalizations per year, stroke or acute chest syndrome, and severe or symptomatic anemia (Hb Statistical analysis

The values were expressed as a mean and 95% confidence interval of the mean; the paired Student's t-test was used to determine the level of significance of differences between the biological parameters, before and after HU treatment. P

The mean initial hemoglobin level was 9.15 g/dL. After one year of HU treatment, the mean hemoglobin level increased to 9.98 g/dL .The difference was not significant (P = 0.25). The mean initial MCV was 82.57 fL. After one year of HU therapy, it increased to 89.87fL. This change was highly significant (P et al., similar results were reported, but they did not report lowering of the annual sickle cell crisis. [17] We found a significant decrease in the number of sickle cell crisis and a marked lowering of annual hospital admissions. In a similar study by Ferster et al., with five years of treatment with HU, the results were similar to our study, but significant results were obtained only after a period of two years. [18],[19]

Allogenic BMT remains the only curative therapy in severe SCD, [19],[20] but in case of patients lacking an HLA-identical sibling, refusing the BMT procedure, or those too old for BMT, or in whom other contraindications exist; HU is the only drug that has proven to modify the disease at short- or middle-term with acceptable toxicity.

HU increases the fetal hemoglobin production in SCD. It promotes fetal hemoglobin production via reactivation of the gamma-globin gene. A series of clinical trials with HU for SCD proved that this medicine is effective and significantly reduces painful crises, occurrence of chest syndrome, and the frequency of transfusions. [21],[22]

In our experience, HU therapy was safe with no clinically significant hematopoietic depression requiring cessation of drug therapy. Most of the patients were maintained on doses of 20 to 25 mg/kg per day throughout the entire follow-up period, without any evidence of loss of efficacy, as assessed by the hematological parameters, annual hospitalization rate, and crisis rate. A study by Zamani et al., reported a well-tolerated five-year HU therapy with only transient thrombocytopenia and Steinberg et al., also reported the same result with a nine-year HU therapy. [10],[23] Contrary to this a case report by Issaivanan et al., reported a 10-year-old boy with chronic myelogenous leukemia who presented with hyperpigmentation of the skin and nails three months after the start of hydroxyurea therapy. [24]

Compliance with HU therapy is important for achieving a sustained hematological effect in patients with SCD, and this requires a coordinated effort by the medical team and frequent contact with patients and families to provide support and encouragement.

The potential for using long-term HU therapy to reduce the morbidity and mortality of children with SCD requires additional and careful investigation, but HU currently provides the best available strategy to achieve hematological and clinical improvement of the disease.


We found a significant reduction in hospital admissions, increased intervals between transfusions, reduction in overall sickle cell crisis, and associated improvement in HbF% in SCD treated with HU. The outcome of the present study and the available evidences recommend a wider adoption of HU for treatment in high-prevalence areas.


We are grateful to Dr. SL Adile, Director, Medical Health Education, Government of Chhattisgarh, and Nodal Officer, Autonomous Society, Government Medical College, Jagdalpur (CG) without whose inspiration and support this study may not have been possible.


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