Risk factors for discontinuing drug therapy among

Authors: Farasat A S Bokhari Frank Heiland Peter Levine G Thomas Ray

Publish Date: 2008/06/19

Volume: 8, Issue: 3, Pages: 134-158

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Abstract

Compliance with drug therapy is of major concern to clinicians as well as policy makers since uncontrolled symptoms due to noncompliance present health risks for patients and may lead to social costs Noncompliance comes in the form of skipped dosages as well as discontinuation well before a clinician deems it appropriate The problem is especially severe in behavioral disorders among children where the symptoms can last well beyond adolescence We use pharmacy dispensing and clinical diagnosis data on children diagnosed with attentiondeficit hyperactivity disorder ADHD and who are on ADHDrelated medications The paper shows how the pharmacy refill data fit naturally into a discrete time hazard rate framework and then compares estimates from alternative definitions of discontinuation We use a long followup period up to 6 years allow for a flexible duration dependence and account for unobserved heterogeneity The expected duration is about 18 months with significant differences across race gender copays medication switching and seasonality We find that AfricanAmerican Hispanic and Asian children are about 39 more likely on average to quit therapy in a given month than white children Similarly compared to a child that initiates drug therapy at age 9 a child that starts therapy at age 10 is 264 more likely to discontinue at any given time Earlier literature using the hazard approach reports smaller associations between these covariates and durations We show that this could be because of ignored unobserved heterogeneity use of a relatively short followup study design and monotonic duration dependence Finally our results are of particular relevance to clinicians as well as to policy makers given recent changes in federal and state policies that may make early detection and diagnosis of ADHD among children less likelyThis study was funded in part by a grant from the National Institute of Mental Health 1R01 MH06708401 MH1 SRVC 01 and in part by the Economics Department at Florida State University Special thanks to Nadine Zubair Gary Fournier Rick Mayes Sara Zubair and participants in the grant application including Tim Brown Lisa Croen Laurie Habel Stephen Hinshaw Tehwei Hu Richard Scheffler Susan Stone for their helpful comments and reviews Finally we would like to acknowledge helpful comments and several insights from two anonymous referees of the journal The usual disclaimer appliers

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