Study objective: To examine adherence measures with different stimulants in children and adolescents.
Design: Retrospective analysis.
Data source: Texas Medicaid prescription claims database.
Patients: A total of 9549 patients aged 5-18 years with attention-deficit-hyperactivity disorder.
Measurements and main results: Paid prescription claims for newly started stimulants during the 2001-2002 school year were extracted from a database; 28,344 prescriptions (9549 patients) were available for analysis. Adherence was evaluated based on the drug therapy prescribed (i.e., mixed amphetamine salts, immediate-release methylphenidate, and extended-release methylphenidate-OROS [oral-osmotic formulation]) and the age and sex of the patient. Adherence measures were persistence and medication possession ratio (MPR). Persistence was higher for extended-release methylphenidate-OROS (0.50 +/- 0.33) than for mixed amphetamine salts (0.42 +/- 0.29) or immediate-release methylphenidate (0.37 +/- 0.26; p < 0.001). The MPR was also higher for extended-release methylphenidate-OROS (0.76 +/- 0.37) than for mixed amphetamine salts (0.73 +/- 0.37) or immediate-release methylphenidate (0.69 +/- 0.37; p < 0.001). Patients aged 5-9 years had equal or better persistence and MPR than those aged 10-14 and 15-18 years (p < 0.001). No sex-related differences in adherence were observed.
Conclusion: Adherence measures in our study were low. Although they were significantly better for extended-release methylphenidate-OROS than the other stimulants, the clinical significance of these differences are unclear. Further research should be conducted regarding pharmaceutical products, administration methods, and clinical interventions that may enhance adherence.