• Fadia T Shaya, Steven Blume, Anna Gu, Teresa Zyczynski, and Zhanna Jumadilova.
• Center on Drugs and Public Policy, University of Maryland School of Pharmacy, Baltimore, USA.
• Am J Manag Care. 2005 Jul 1; 11 (4 Suppl): S121S129S121-9.

Statement Of Problem And RationaleThe management of chronic conditions, such as overactive bladder (OAB), is often limited by lack of patient adherence to medication. This article compares persistence rates among Medicaid patients who were prescribed 1 of 3 drugs for treatment of OAB: 2 long-acting agents with once-daily dosing, tolterodine tartrate extended-release capsules (tolterodine ER) and oxybutynin chloride extended release (oxybutynin ER), and oxybutynin immediate release (oxybutynin IR), requiring 3 tablets daily.MethodologyThe study population was comprised of continuously enrolled Medicaid managed care patients filling prescriptions for tolterodine ER, oxybutynin ER, or oxybutynin IR between January 1, 2000, and December 31, 2003. Patients taking any OAB drug in the first 6 months of their observed period of enrollment were excluded to capture new users only. Using survival analyses adjusted for age, sex, and race, the rates of persistence by drug were analyzed. Possession time, the degree to which patients keep medication available even though they may not be taking it daily as prescribed, was also measured.ResultsOf 1637 patients (75% women, 45% African American, 26% younger than 18 years of age), 182 were started on tolterodine ER, 215 on oxybutynin ER, and 1240 on oxybutynin IR. Only 32% of those taking oxybutynin IR and 44% of those taking either long-acting agent remained adherent past 30 days. Of those remaining after 30 days, the risk of nonadherence was higher for oxybutynin ER than for tolterodine ER (hazard ratio = 1.47; 95% confidence interval, 1.01-2.14).ConclusionPersistence rates are better for patients taking drugs with once-daily dosing, but there is a need for a better understanding of non-persistent patients.

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