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Supplements New Perspectives on Overactive Bladder: Quality of Life Impact, Medication Persistency, and Treatmen
New Perspectives on Overactive Bladder: Quality of Life Impact, Medication Persistency, and Treatment Costs
C. Daniel Mullins, PhD; and Leslee L. Subak, MD
Persistence With Overactive Bladder Pharmacotherapy in a Medicaid Population
Fadia T. Shaya, PhD, MPH; Steven Blume, MS; Anna Gu, MA; Teresa Zyczynski, PharmD, MBA, MPH; and Zhanna Jumadilova, MD, MBA
The Impact of Urinary Incontinence on Quality of Life of the Elderly
Yu Ko, MS; Swu-Jane Lin, PhD; J. Warren Salmon, PhD; and Morgan S. Bron, PharmD, MS
Safety and Tolerability of Tolterodine for the Treatment of Overactive Bladder in Adults
Richard G. Roberts, MD, JD; Alan D. Garely, MD; and Tamara Bavendam, MD
Medical Costs After Initiation of Drug Treatment for Overactive Bladder: Effects of Selection Bias on Cost Estimates
Nicole M. Nitz, PhD; Zhanna Jumadilova, MD, MBA; Theodore Darkow,   PharmD; Jennifer R. Frytak, PhD; and Tamara Bavendam, MD
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Economic Impact of Extended-release Tolterodine versus Immediate-and Extended-release Oxybutynin Among Commercially Insured Persons With Overactive Bladder
Sujata Varadharajan, MS; Zhanna Jumadilova, MD, MBA; Prafulla Girase, MS; and Daniel A. Ollendorf, MPH
Treatment of Overactive Bladder: A Model Comparing Extended-release Formulations of Tolterodine and Oxybutynin
Eleanor M. Perfetto, PhD; Prasun Subedi, MS; and Zhanna Jumadilova, MD, MBA
PARTICIPATING FACULTY

Economic Impact of Extended-release Tolterodine versus Immediate-and Extended-release Oxybutynin Among Commercially Insured Persons With Overactive Bladder

Sujata Varadharajan, MS; Zhanna Jumadilova, MD, MBA; Prafulla Girase, MS; and Daniel A. Ollendorf, MPH

Objective: To examine levels of persistence and compliance as well as the economic impact of extended-release tolterodine (tolterodine ER) versus immediate-and extended-release oxybutynin (oxybutynin IR or oxybutynin ER) among commerciallyinsured patients with overactive bladder (OAB).

Methods: Patients with OAB who initiated tolterodine ER, oxybutynin IR, or oxybutynin ER between January 2001 and December 2002 were identified from the PharMetrics Patient-Centric database; the first medication used in this timeframe was used for treatment group assignment (ie, patients were only in 1 group). Exploratory assessment of persistency and compliance was conducted among all treated patients: subjects were matched 1:1 based on the estimated propensity score for tolterodine ER in remaining analyses. Measures included patient characteristics as well as levels of medication, outpatient and inpatient resource utilization, and costs. Primary comparisons were made descriptively; costs were evaluated using generalized linear models with a gamma distribution and log-link function.

Results: Compliance did not differ between tolterodine ER (77.4%) and oxybutynin ER (74.3%), but was lower for oxybutynin IR (60.9%). Mean (+ standard deviation) duration of therapy was higher for tolterodine ER (139 + 132 days) versus oxybutynin ER (115 + 122) and oxybutynin IR (60 + 85). Totals of 7257 and 5936 matched pairs were available for tolterodine ER versus oxybutynin ER and oxybutynin IR comparisons, respectively. The mean age was 54 years in all groups; the majority was women. Utilization of outpatient and inpatient medical services was consistently lower among tolterodine ER patients in both comparisons. Total costs were slightly lower for tolterodine ER versus oxybutynin ER ($8303 + $18 802 vs $8862 + $18 684) and oxybutynin IR ($9975 + $24 860 vs $10 521 + $22 602); differences were significant after multivariate adjustment.

Conclusions: Use of tolterodine ER results in comparable compliance to oxybutynin ER and longer duration of use relative to either form of oxybutynin. In addition, tolterodine ER may be costeffective relative to oxybutynin IR or oxybutynin ER among commercially-insured persons with OAB.

(Am J Manag Care. 2005;11:S140-S149)


Overactive bladder (OAB) is a common and distressing medical condition resulting in symptoms that include urgency, with or without urinary frequency, and/or urgency incontinence.1 It is estimated that 16% to 17% of Americans suffer from OAB.2

In general, the symptoms of OAB can have a debilitating effect on an individual by disrupting quality of life (QOL), sleep patterns, and mental health.3 Costs associated with OAB also are substantial. In 2000, the total direct and indirect cost of OAB in the United States was estimated at $12.02 billion, with $9.17 billion and $2.85 billion at the community and institution levels respectively.4 Costs are expected to escalate even further as the prevalence of OAB in the United States increases because of the aging of the population.

The goals of OAB treatment are to reduce symptomalogy and improve QOL. There are several treatment options available for this condition, including behavioral modification, pharmacotherapy, and surgical intervention, with the most common being behavioral therapy and pharmacotherapy.5 Antimuscarinic agents have remained the mainstay of pharmacotherapy for OAB since the launch of oxybutynin in the 1970s. Although immediate-release oxybutynin (oxybutynin IR) has proved effective in relieving the symptoms of OAB, it is associated with many undesirable side effects, subsequently reducing patient adherence and compliance with time.6 During the past several years, treatment for OAB has expanded to include newer agents that reduce major side effects and thereby improve adherence to therapy. Newer extended-release antimuscarinics, such as tolterodine, and the extended-release form of oxybutynin (oxybutynin ER) have demonstrated improved efficacy, convenience, and a tolerability profile better than their immediate-release counterparts by offering once-daily dosing and diminished side effects.6-8 Several trial-based studies have been conducted in the past that compare efficacy, costs, and adherence in oxybutynin IR and immediate-release tolterodine (tolterodine IR) relative to their extended-release forms.9,10 The results of another recent analysis of data that evaluated extended-release tolterodine (tolterodine ER) and controlled-release oxybutynin by using a 4-way crossover design indicated that tolterodine ER was as effective as the controlled-release oxybutynin but with a better tolerability profile.11

Although there are numerous clinical studies that focus primarily on the cost and efficacy of immediate-release forms or the extended-release versions of oxybutynin and tolterodine separately,12-17 to date there has been no large-scale retrospective study that comprehensively assesses relevant outcomes associated with tolterodine ER in comparison to both oxybutynin IR and oxybutynin ER. Additionally, the availability of various treatment options and the potential cost implications associated with these alternatives give rise to the need for comparisons from a typical US clinical practice perspective (ie, nonclinical trial population and setting). The present study examines adherence to OAB pharmacotherapy as well as the impact of tolterodine ER versus oxybutynin IR and oxybutynin ER on the levels of resource utilization and cost in a large commercially-insured population with OAB.

Methods

Data Source. Data were obtained from the PharMetrics Patient-Centric database, which is comprised of fully adjudicated medical and pharmaceutical claims for more than 46 million unique patients from 82 health plans across the United States. The database includes both inpatient and outpatient diagnoses (in International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] format) and procedures (in Current Procedural Terminology 4 and Health Care Common Procedural Coding System formats) as well as both standard and mail order prescription records. Data on prescription records include the National Drug Code as well as days supplied and quantity dispensed. Both health plan paid and charged amounts are available for all services rendered as well as dates of service for all claims. Additional data elements include demographic variables (ie, age, sex, geographic region), plan type (eg, health maintenance organization [HMO], preferred provider organization [PPO]), payor type (eg, commercial, self-insured), provider specialty, and plan enrollment dates.

Sample Selection. All patients diagnosed with OAB (ICD-9-CM 596.5X [excluding 596.53, 596.54], 788.3X, 788.41, 788.43) and at least 1 pharmacy claim for any of the medications of interest (ie, tolterodine ER, oxybutynin ER, oxybutynin IR) between January 1, 2001, and December 31, 2002, were initially selected for inclusion in the study sample. The date of first medication use served as the patient's index date. Preindex and follow-up periods of 12 months' duration each were created in relation to the index date. Claims for these patients were then accumulated spanning the period of January 1, 2000, to December 31, 2003.

Patients not continuously eligible for drug and health benefits during their entire preindex and follow-up periods were excluded. Patients who had evidence of using an OAB drug of interest during the pre-index period were also excluded. In addition, patients participating in plans without pharmacy benefits were excluded, as were patients aged 65 years or older who were not enrolled in a Medicare "risk" plan (ie, an agreement by which a commercial health plan agrees to assume full financial risk for the coverage of a Medicare beneficiary); the latter exclusion was implemented to ensure that elderly patients had complete reporting of medical and pharmaceutical utilization.

All patients treated with tolterodine ER, oxybutynin ER, or oxybutynin IR who had valid information on pharmacy claims were selected for the persistency and compliance analyses. Matched pairs of patients were created to compare outcomes, resource utilization, and costs in comparable groups. To control for potential differences between treatment groups, propensity scores were calculated using multivariate logistic regression and a stepwise selection procedure. A propensity score represents a specific patient's fitted probability (ie, propensity) of receiving a given treatment option and is calculated by summing coefficient values for a list of potential confounding variables. Use of these scores confers the advantage of having a single estimate available to control for multiple differences between treatment groups in a matched-pairs analytic design.18

Demographic and clinical characteristics as well as pre-index variables were introduced as covariates into the model using stepwise logistic regression techniques; those achieving significance at a level of P <.05 were retained. The outcome of interest was the propensity for, or likelihood of, treatment with tolterodine ER. Separate propensity scores were created for each set of pair-wise comparisons. Thus, patients treated with tolterodine ER were matched on a 1:1 basis to patients treated with oxybutynin ER and oxybutynin IR, and matching was conducted based on a difference of + 0.01 in this probability.

Measures. The primary measures of interest for this study included persistence and compliance as well as resource utilization and costs of OAB-related and unrelated services, which were all measured over 12 months of follow-up.

A number of demographic and clinical characteristics, including age, sex, health plan type (eg, HMO, PPO), geographic region, presence of selected pretreatment comorbidities (ie, Alzheimer's disease, chronic obstructive pulmonary disease, congestive heart failure, diabetes, hypertension, ischemic heart disease, multi-infarct dementia, multiple sclerosis, Parkinson's disease, prostate hyperplasia, stroke, urinary retention, urticaria), and comorbidity score (ie, Charlson Index with Deyo modification),19 were tracked for each treatment group. Among patients receiving an OAB drug of interest, persistence and compliance were measured. Persistence was calculated based on the time (in days) from therapy initiation until the first discontinuation. First discontinuation was defined as a gap in therapy exceeding 2 times the therapy days supplied on the previous prescription. Compliance was expressed as a ratio of the number of therapy days supplied divided by the persistence measure described above. Persistence was also calculated on a monthly basis over a 12-month follow-up period from therapy initiation. Each patient's persistence duration was recorded as a data point in the correct range (ie, months 1-12) for when therapy was discontinued.

OAB-related and -unrelated resource utilization and costs were assessed during the follow-up period and included pharmaceutical claims indicated for OAB as well as all other pharmacy claims and medical claims (office management, emergency room, other outpatient, inpatient) related and unrelated to OAB.

Where relevant, medical claims were defined as OAB-related versus all others based on the presence of an OAB diagnosis. Costs were estimated based on health plan payments for medications and services rendered and net of patient responsibility (ie, copayment, coinsurance, and/or deductible). Costs were updated as necessary using the medical care component of the US Consumer Price Index. Non- OAB-related claims also were tallied and were categorized in similar fashion (ie, pharmacy, outpatient/emergency room, inpatient).

Analyses. Differences in patient characteristics, as well as costs during follow-up, were assessed using inferential statistics (ie, chi-square tests for categorical variables and Wilcoxon rank-sum tests for continuous variables); P <.05 was deemed to be statistically significant. Generalized linear models were also used to compare total healthcare costs between the matched patient subgroups. Independent variables in the base models included age, sex, health plan type, geographic region, treating physician specialty, pre-index comorbidities, and pre-index Charlson Comorbidity score. All analyses were conducted using Statistical Analysis Software ([SAS], SAS Institute, Cary, NC), Version 8.2.

Results

 
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