Introduction: Hydroxyurea is a well-established disease-modifying agent for children and adults with sickle cell disease (SCD). Its effectiveness in reducing painful crises, acute chest syndrome, hospital admissions, and the frequency of blood transfusions, as well as in improving overall quality of life, is well-documented. Despite these benefits, adherence to hydroxyurea therapy remains a significant challenge, particularly in low- and middle-income countries. Medication adherence, defined as the extent to which patients take their medications as prescribed, is crucial for maximizing hydroxyurea's therapeutic benefits. Poor adherence is associated with reduced medication effectiveness, adverse disease outcomes, and increased healthcare costs. This study assessed hydroxyurea adherence and identified barriers and enablers among children and adolescents with SCD in Jos, Nigeria.

Methods: This cross-sectional study included SCD patients aged 1-21 years who had been on hydroxyurea for at least six months. Data were collected using a structured questionnaire covering pre-hydroxyurea clinical status, hydroxyurea intake history, perception of its effectiveness, and adherence barriers and enablers. Adherence was measured using the Morisky Medication-Taking Adherence Scale (MMAS-4), a widely used, generic self-reported tool designed to assess medication-taking behavior among patients through four key questions. It asks if patients ever forget to take their hydroxyurea, have trouble remembering to take their medication, stop taking hydroxyurea when they feel better, or discontinue hydroxyurea when they feel worse. Responses are scored as “Yes” = 0 and “No” = 1, with total scores ranging from 0 (poor) to 4 (good) adherence. Pre-hydroxyurea clinical status was classified as mild, moderate, and severe using the severity of SCA scoring system by Adegoke et al. Ethical clearance was obtained from the Research and Ethics Committee of Jos University Teaching Hospital. Written informed consent was obtained from parents and assent from participants aged 7 years and above. Descriptive statistical analysis was conducted using SPSS version 23.0 for Windows.

Results: A total of 172 HbSS patients (52.9% males) participated, with a mean age of 10.4 ± 5.1 years, a mean hydroxyurea intake duration of 32.5 ± 17.4 months, and a mean maximum dosage of 21.6 ± 5.4 mg/kg. The pre-hydroxyurea clinical status of participants was classified as mild (23.8%), moderate (42.4%), and severe (33.7%). Among patients who experienced two or more clinical events before starting hydroxyurea, 92.8% (142/153) reported a reduction in vaso-occlusive crises, 84.1% (111/132) reported fewer hospital admissions, and 73.3% (55/75) noted a decreased need for blood transfusions. Additionally, 96.1% (150/156) affirmed an overall improvement in general well-being.

Approximately 3% (5/172) discontinued hydroxyurea due to side effects or efficacy concerns. Among the remaining 167 participants, 76% exhibited good adherence according to the MMAS-4. In response to specific questions, 10.8% (18/167) did not take hydroxyurea at all in the previous one week, while 58.7% (98/167) missed no doses. Barriers to regular hydroxyurea intake among the 167 participants included forgetting to take medication (56.9%), cost (40.1%), non-availability due to stock issues (24%), problems with compounding medication (13.8%), medication fatigue (12%), feeling of wellness (12%), side effects (2.4%), and doubts about efficacy (1.2%). Motivators for adherence among the 127 participants with good adherence ratings included desire to maintain good health (83.8%), doctor's counselling (46.1%), and family support (40.7%).

Conclusion: This study highlights significant barriers and enablers to hydroxyurea adherence among children and adolescents with SCD in Jos, Nigeria. While the majority of patients recognize the clinical benefits and exhibit good adherence, challenges such as forgetfulness, medication costs, and availability persist. Addressing these barriers through targeted interventions can improve adherence, thereby enhancing patient outcomes and reducing healthcare costs.

Keywords: Hydroxyurea, sickle cell disease, adherence, barriers, enablers

Disclosures

No relevant conflicts of interest to declare.

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2024
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