Monitoring toxicity, impact, and adherence of hydroxyurea in children with sickle cell disease

Hydroxyurea (HU) is underutilized in sickle cell disease (SCD). Patient adherence with taking HU and with required drug monitoring is a provider perceived barrier to HU utilization (Brandow et al., Am J Hematol 2010;85:611-613; Brawley et al., Ann Internal Med 2008;148:932-938; Lanzkron et al., J Natl Med Assoc 2008;100:968-973; Zumberg et al., Am J Hematol 2005;79:107-113). To determine process issues that may contribute to these barriers, we sought to: (1) describe how providers monitor and adjust HU dosing in children with SCD in clinical practice and (2) identify providers' methods of assessing HU adherence. A pilot-tested survey was emailed to American Society of Pediatric Hematology/Oncology (ASPHO) members. Descriptive statistics were performed. Thirty-one percent (n = 350) of 1,128 surveys were returned; 63% (220 of 350) of respondents provided care for children with SCD. Most providers (64.7%) follow labs monthly and almost half (41.9%) see patients monthly. The majority (61.9%) adjusted HU dosing using maximum tolerated dose commonly determined using ANC (27.9%), platelets (26.5%), and WBC count (11.2%). Adherence was primarily assessed using patient interview (84.2%), MCV (75.3%), and HbF levels (70.7%). The majority of providers performs monthly monitoring and assess HU adherence using unreliable methods. Determining optimal frequency of monitoring HU and more reliable methods of assessing adherence are essential to balancing safety and the elimination of barriers to promote HU utilization.