Anticholinergics have a high discontinuation rate and many associated unfavorable adverse effects such as dry mouth, constipation and cognitive changes. [1] Mirabegron was approved by the FDA in 2012 as the first beta-3 agonist to treat overactive bladder and has been shown to have an increased persistence of use with less anticholinergic side effects. [2] This study aims to examine how prescribing patterns have changed since the approval of mirabegron.

The 2013-2017 Medicare Part D Public Use File was used to identify all prescribers of overactive bladder medications including oxybutynin, tolterodine, trospium, darifenacin, solifenacin, fesoterodine, and mirabegron. The Medicare Part D database contains information of prescriptions made by physicians that were paid under the Medicare Part D Prescription Drug Program. Included in the database is National Provider Identifier, provider name, specialty, brand drug name, generic drug name, prescription claim count and total drug cost. Total claim count includes original prescriptions and refills. The number of days supplied by each claim is not specified in this data point. The total drug cost includes ingredient cost, dispensing fee, sales tax and any applicable vaccine administration fees and is based on the amounts paid by the Part D plan, Medicare beneficiary, government subsidies and any other third-party payer. The number of claims and total annual expenditure for each medication for all prescribers, non-urologists, and urologists were analyzed from 2013-2017.

This study used a public database and therefore was exempt from Institutional Review Board approval.

In 2013, 124,702 prescribers (8,476 urologists and 116,226 non-urologists) made 7,688,033 overactive bladder medication claims. By 2017, 131,474 prescribers (8,705 urologists and 122,769 non-urologists) made 8,817,780 overactive bladder medication claims. Among all providers, oxybutynin was consistently the most prescribed overactive bladder medication each year.  In 2013, 3,978,380 claims of oxybutynin were made, which consisted of 51.7% of OAB medication claims and in 2017, 4,754,643 claims were made comprising of 53.9% of all overactive bladder medications in 2017. (Figure 1) Solifenacin was the second most prescribed overactive bladder medication in 2013, however the number of prescriptions decreased from 1,854,902 in 2013 to 1,278,038 in 2017. From 2013 to 2017, the number of claims and proportion of overactive bladder medication claims for mirabegron rose each year. In 2013, 140,401 claims were made for mirabegron which was 1.8% of all overactive bladder medication claims. By 2017, 1,617,439 claims were made for mirabegron which was 18.3% of all overactive bladder medication claims making it the 2nd most prescribed overactive bladder medication for urologists and non-urologists.

The total annual expenditure for overactive bladder medications increased from $1.016 billion to $1.608 billion from 2013 to 2017. There was a linear increase in the total annual expenditure on mirabegron over the years. By 2017, mirabegron had the highest expenditure of any overactive bladder medication for all practitioners and urologists. For all practitioners, the expenditure of mirabegron was $658.6 million which was 41% of overactive bladder medication expenditure. For urologists, mirabegron expenditure was $297.7 million, 51.2% of overactive bladder medication expenditure. (Figure 2)

Mirabegron usage quickly increased from 2013 to 2017 making it the 2nd most prescribed overactive bladder medication. This may be related to decreased antimuscarinic side effects and marketing strategies from pharmaceutical companies. [3]

Despite the availability of mirabegron and more selective anticholinergic agents with a more favorable side effect profile, oxybutynin continued to be the most prescribed overactive bladder medication. Possible reasons for this result include habitual prescribing since oxybutynin was one of the first overactive bladder agents available and increased costs of newer medications. 

From 2013 to 2017, overactive bladder medication Medicare expenditure increased by more than $500 million.

Mirabegron utilization and the total expenditure has steadily increased each year since its approval, making it the 2nd most prescribed overactive bladder medication by 2017. Oxybutynin continued to be the most prescribed overactive bladder medication from 2013-2017

Wagg, A., Compion, G., Fahey, A. et al.: Persistence with prescribed antimuscarinic therapy for overactive bladder: a UK experience. BJU International, 110: 1767, 2012
Chapple, C. R., Nazir, J., Hakimi, Z. et al.: Persistence and Adherence with Mirabegron versus Antimuscarinic Agents in Patients with Overactive Bladder: A Retrospective Observational Study in UK Clinical Practice. European Urology, 72: 389, 2017
Modi, P. K., Wang, Y., Kirk, P. S. et al.: The Receipt of Industry Payments is Associated With Prescribing Promoted Alpha-blockers and Overactive Bladder Medications. Urology, 117: 50, 2018