Long-term adherence to antimuscarinic therapy in everyday practice: a systematic review

Antimuscarinic drug treatment is known to have side effects and, consequently, poor adherence in therapeutic regimens. In this systematic review we study the long-term (greater than 6 months) adherence to antimuscarinic drugs in daily clinical practice, and identify factors contributing to poor adherence and persistence.

This systematic review was conducted according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. A literature search was performed using PubMed® and Embase™ using synonyms for incontinence, overactive bladder and antimuscarinics combined with synonyms for medication adherence. We chose to include only pharmaceutical database studies (using prescription/insurance claim data) and patient self-report studies, using established pharmacoepidemiological parameters such as persistence rate and medication possession rate.

A total of 1,245 titles were screened, of which 102 abstracts were assessed. Fourteen studies were ultimately included, comprising 190,279 unique patients (mean age 69.5 years). Regardless of which specific antimuscarinic drug is studied, persistence rates are usually poor. Considering all drugs together, median persistence rates were 12.0% to 39.4% (with an outlier of 75.5%) at 12 months, 8.0% to 15.0% at 18 months and 6.0% to 12.0% at 24 months. At 36 months persistence rates ranged from 0.0% (darifenacin) to 16.0% (trospium). Mean reported medication possession rates were also low, with a mean of 0.37 at 12 months. Risk factors for discontinuation were identified, with the most important being younger age group, use of oxybutynin and use of immediate release formulations.

Improvement in adherence and persistence with antimuscarinic medication should be an important goal in the development of new drugs for overactive bladder and urinary incontinence.