Long-term antimuscarinic use in OAB patients is poor, according to a new study

Key Points

San Francisco-Long-term, reliable use of antimuscarinics in patients with overactive bladder is significantly lower than past clinical trials have suggested, according to results of a community-based study presented at the 2009 International Continence Society annual meeting.

Newer, long-acting antimuscarinic agents now make it easier for patients to take a single daily dose and, when necessary, to maximize efficacy with selective dose escalation. Yet, according to investigators at Guy's and St. Thomas' NHS Foundation Trust, London, poor adherence to medication is commonly encountered and associated with inadequate treatment in clinical practice despite clinical trial data that suggest otherwise. Currently, no guidelines exist for the optimum duration of antimuscarinic medication use in clinical practice, also a possible factor in both short- and long-term adherence to treatment, said first author Ramandeep Basra, MBBS, a clinical research fellow who conducted the study with Con Kelleher, MD, and Vik Khullar, MD.

Thus, this study's aim: to determine the use of antimuscarinic medication in patients with OAB in a real-world setting.

Beginning in May 2006, 251 women were recruited to participate in a community-based, 2-year, prospective study. All participants were previously diagnosed with idiopathic OAB and had been referred from primary care practices to two tertiary urogynecology centers. Mean age was 55 years. Following baseline and 6-week visits, patients were asked to return for follow-up visits every 3 months for a minimum of a year. All patients were offered long-acting, once-daily antimuscarinic medications-solifenacin (VESIcare), tolterodine (Detrol LA), darifenacin (Enablex), oral oxybutynin (Ditropan XL), or transdermal oxybutynin (Oxytrol)-with solifenacin and extended-release tolterodine used as the first-line agents. (A number of newer agents were not studied.)

In addition to standard demographic and concurrent medication data collected early on, patients filled out a series of questionnaires at each study visit, including the Patient Perception of Bladder Condition (PPBC) scale and the King's Health Questionnaire (KHQ).

In all, 133 patients (53%) completed 12 months of follow-up; 68 patients (27%) completed 24 months of follow-up visits. Eleven patients (4%) failed to complete their baseline assessment, and 107 patients (43%) dropped out of the study within 6 months.

Increased severity of OAB symptoms, as reported on the PPBC and KHQ, was associated with using a larger number of antimuscarinic agents, escalation of drug dose, and a longer duration of medication.

Mean duration of medication use was 17.5 weeks and 27.25 weeks in patients completing 12- and 24-month follow-ups, respectively. The percentage of patients requiring dose escalation was significantly lower than in clinical studies. In addition, after a year of treatment, just 20% of the study patients were still using antimuscarinic medications. By 2 years, as the study wrapped up, all patients had ceased using the drugs.

"We didn't expect drug adherence to be really high, but it was surprising that people weren't renewing their prescriptions on a regular basis," Dr. Basra said. "Maybe giving patients a prescription without specific guidance about how long to use their medication is insufficient. We may need to tailor our management differently to find the best way to get patients to engage in their own treatment so they can get better."