Chua KJ, Patel HV, Tabakin A et al: Yearly trends of overactive bladder medication usage. Urol Pract 2021; 8: 546.

Initial treatment of overactive bladder (OAB) consists of behavioral modifications followed by pharmacological therapy including anticholinergics and beta-3 adrenoreceptor agonists.¹ While these 2 classes of medication have demonstrated similar efficacies, anticholinergics have been associated with a poorer tolerability due to side effects including dry mouth, constipation and cognitive impairment.² Importantly, recent studies have highlighted the increased association of dementia with anticholinergic usage, particularly for less selective anticholinergics such as oxybutynin and tolterodine, and encouraged avoidance of anticholinergics especially in the elderly population.³ In 2012, mirabegron was the first U.S. Food and Drug Administration approved beta-3 adrenoreceptor agonist to be developed for treatment of OAB.⁴ Beta-3 agonists have demonstrated similar efficacy to antimuscarinics in managing OAB symptoms but are associated with few side effects⁴ and carry an excellent safety profile.^5,6

In our study, the Medicare Part D database from 2013 to 2017 was used to trend the number of prescriptions made for different OAB medications over time.⁷ Our hypothesis was that less selective anticholinergics such as oxybutynin would decrease in usage while mirabegron would increase given its lack of anticholinergic side effects. The CMS (Centers for Medicare and Medicaid Services) Medicare Provider Utilization and Payment Data: Part D Prescriber Public Use File Database was used to extract information regarding prescriptions made by providers that were paid under the Medicare Part D Prescription Drug Program from 2013 to 2017.⁸ This database contains National Provider Identifier, provider name, specialty, generic drug name, prescription claim count, prescription claim count for patients whose age is 65 or older and total drug cost. OAB medications were identified by their generic drug name and included oxybutynin, tolterodine, trospium, darifenacin, solifenacin, fesoterodine and mirabegron. For each type of provider, the total number of claims and total expenditure of each OAB medication was calculated and compared between each year.

From 2013 to 2017, the number of OAB medication-prescribing providers increased from 124,702 (8,476 urologists and 116,226 non-urologists) to 131,474 (8,705 urologists and 122,769 non-urologists). In 2013, there was a total of 7,688,033 claims made for OAB medications. Whereas oxybutynin comprised 51.7% of these claims (3,978,380; fig, 1), mirabegron was one of the least prescribed comprising only 1.8% of claims (140,401). In 2017, the number of OAB medication claims increased to 8,817,780. Oxybutynin remained the most prescribed OAB medication, comprising 53.9% of all claims (4,754,643). There was a linear increase of mirabegron claims each year, and by 2017 it was the second most prescribed OAB medication with 18.3% of claims (1,617,439). Solifenacin was the second most prescribed medication in 2013, but its usage decreased each year. Trospium, darifenacin and fesoterodine were consistently among the least prescribed OAB medications each year. These trends did not change across census regions or when accounting for patients ≥65 years old. In 2017, 50.8% of claims were for oxybutynin in patients who were ≥65 years old. Urologists alone displayed similar trends but used a lower proportion of oxybutynin. By 2017, urologists made 934,498 and 649,703 claims for oxybutynin and mirabegron, respectively, comprising 41.4% and 28.8% of all urologist OAB medication claims.

Figure 1. Yearly trends of OAB medication claims.

Total expenditure on OAB medications also increased from $1.016 billion to $1.608 billion from 2013 to 2017 (fig. 2). In 2013, solifenacin had the highest total expenditure consisting of 44.1% of OAB medication costs ($447.9 million) while oxybutynin consisted of only 17.7% of the total expenditure ($179.8 million). The total expenditure of mirabegron was 3.7% of OAB medication costs ($37.7 million) in 2013, but by 2017 mirabegron had the highest total expenditure of OAB medications at 41% ($658.6 million).

Figure 2. Yearly trends of expenditure on OAB medications.

Our study highlights the rapid increase in mirabegron utilization over the past several years, despite it having the highest expenditures out of all other OAB medications. Ultimately, mirabegron may be more cost-effective in treating OAB than anti-cholinergic options, given its association with improved persistence of use and tolerability.⁹ However, our results also demonstrate that oxybutynin is still the most frequently used OAB medication and that its usage continues to rise. Interestingly, more selective anticholinergics were among the lesser used options. Possible reasons for this finding include routine prescribing of familiar medications and insurance companies requiring a trial of anticholinergics prior to authorization of mirabegron.¹⁰ As cognitive effects of anticholinergics can lead to hospitalization and higher health care costs, it is important to curb usage of less selective anticholinergics in the elderly. Possible interventions to curb prescribing of nonselective antimuscarinics like oxybutynin include revision of insurance company policies limiting accessibility of beta-3 agonists and selective antimuscarinics and educational programming for primary care physicians and patients led by urologists, advocacy groups, or interdisciplinary taskforce groups regarding antimuscarinic side effects. Additionally, future studies should investigate trends in private insurance databases and the association of each antimuscarinic separately with cognitive side effects as newer, more selective agents may be safer options in elderly patients.