Trospium 60 mg Once Daily (QD) for Overactive Bladder Syndrome: Results from a Placebo-Controlled Interventional Study

A meta-analysis of the placebo response in antimuscarinic drug trials for overactive bladder

Background

The purpose of this analysis was to characterize the placebo response in antimuscarinic drug trials for OAB, based on changes in commonly-used efficacy endpoints.

Methods

Placebo arm data for incontinence episodes, micturitions, voided volume and study characteristics were extracted from randomized placebo controlled antimuscarinic drug trials in OAB, from studies identified in a prior meta-analysis, and from a systematic review of more recently published studies. Relationships between variables were examined using linear regression, and changes in endpoints were analyzed by a meta-analysis approach. The effect of placebo arm size and magnitude of placebo response on probability of successful study outcome was analyzed using an ANOVA model.

Results

Changes in the placebo arms for all 3 endpoints were substantial and statistically significant, and highly heterogeneous. There were significant associations between baseline and change scores for some but not all of the endpoints. More recent studies tended to have more subjects than earlier studies, and there were positive associations between probability of achieving statistically significant results and size of the placebo arm. The magnitude of changes in placebo arms did not appear to influence the likelihood of the study to be statistically significant.

Conclusion

This analysis confirms earlier observation that the placebo response in OAB trials is substantial and highly heterogeneous. There are multiple potential reasons for this; however, these could not be explored in this analysis of study-level data. Two approaches may be used in clinical trials to manage high placebo effect: recruitment of 1) greater numbers of patients and/or 2) more severely affected patients; however, only the former approach is associated with increased probability of successful study outcome.

Baseline incontinence severity is predictive of the percentage of patients continent after receiving once-daily trospium chloride extended release

OBJECTIVE

It has been assumed that a patient's underlying baseline overactive bladder (OAB) incontinence severity is predictive of the resulting efficacy of pharmacological treatment. The objective of this study was to stratify and analyse the effects of baseline incontinence disease severity on the treatment outcome of the percentage of patients continent (PPC) during treatment with once-daily trospium chloride 60 mg extended release (XR).

METHODS

A post hoc analysis was conducted on pooled data from two 12-week, randomised, double-blind phase III studies in the USA in which 1165 patients with baseline urgency, and an average of >or= 1 urge urinary incontinence (UUI) episode/day and >or= 10 toilet voids/day on a 3-day bladder diary, received once-daily trospium chloride 60 mg XR (n = 578) or placebo (n = 587). Patients were stratified by the mean number of UUIs/day (1.0, > 1.0-2.0, > 2.0-5.0 or > 5.0) at baseline. The efficacy parameter that was analysed was complete continence (defined as no UUIs on a 3-day bladder diary collected at week 12 of treatment).

RESULTS

Baseline UUI levels were inversely correlated with the week 12 PPC (p < 0.0001). Post-treatment PPCs were higher with trospium chloride XR vs. placebo at all degrees of severity. Complete continence was achieved in 75% of trospium chloride XR recipients with 1.0 UUI/day at baseline and 48% of those with > 1.0-2.0 UUIs/day at baseline.

CONCLUSIONS

These findings support the assumption that baseline incontinence severity affects the likelihood of achieving continence from OAB therapy, and that patients with less severe OAB (e.g. 1 UUI/day) can expect higher 'dry rates' following treatment (e.g. up to 75%) than those with more severe OAB. This information can provide a useful tool for the physician and patient in establishing expectations during therapy.

Trospium chloride treatment of overactive bladder

OBJECTIVE

To review the pharmacology, pharmacokinetics, safety, and clinical application of trospium chloride for the management of overactive bladder (OAB).

DATA SOURCES

Clinical literature including both primary sources and review articles was accessed through MEDLINE, International Pharmaceutical Abstracts, and Cochrane databases from 1980 through January 8, 2009. Search terms included overactive bladder, urge urinary incontinence, muscarinic receptor antagonists, and urinary frequency. Further data sources were identified from bibliographies of selected articles.

STUDY SELECTION AND DATA EXTRACTION

Basic pharmacology data were extracted from animal studies and pharmacokinetic data were gathered from human studies. Multicenter, parallel, randomized, double-blind, placebo-controlled studies were included to describe the efficacy and adverse effects of trospium.

DATA SYNTHESIS

Trospium chloride is an antimuscarinic agent indicated for the treatment of OAB with symptoms of urge urinary incontinence, urgency, and urinary frequency. Trospium has 3 chemical and pharmacokinetic properties unique among antimuscarinic agents: it is a positively charged quaternary ammonium compound with minimal central nervous system penetration; it is not metabolized by the cytochrome P450 system, resulting in a lower tendency for drug interactions; and it is excreted mainly unchanged in the urine as the active parent compound, providing local activity to achieve early onset of clinical effect and prolonged efficacy. In two 12-week, randomized, placebo-controlled clinical studies in adults with OAB, trospium 20 mg twice daily was more effective than placebo in reducing the number of micturitions per 24 hours, reducing the number of urge incontinence episodes per week, and increasing the volume of urine voided per micturition. Placebo-controlled trials report efficacy with trospium in treatment of OAB; comparative trials with other anticholinergic agents are limited. Current therapy of OAB consists primarily of anticholinergic drugs such as oxybutynin, which are associated with therapy-limiting adverse effects. Because the prevalence of OAB is greatest among the elderly, safety considerations regarding renal function must be noted, with dosage adjustment required in patients with severe renal impairment.

CONCLUSIONS

Whether the pharmacodynamic properties of trospium make it superior to other therapies will require considerable additional experience with the drug. For now, it appears to be a feasible alternative for patients who cannot tolerate oxybutynin.

Current management of overactive bladder

PURPOSE OF REVIEW

The concept of overactive bladder has helped us address the problem of urgency and urge incontinence from a symptomatic perspective. In this review, we provide a critical summary of clinically relevant recent publications, focusing in particular on advances in our understanding of assessment methods and therapeutic interventions for overactive bladder in women.

RECENT FINDINGS

According to current definitions, the prevalence of overactive bladder in western nations is now estimated as 13.0%. Although the prevalence increases with age, the symptoms of overactive bladder may follow a relapsing and remitting course. There has been a proliferation of validated symptom and quality of life measures and increasing sophistication in the analysis of bladder diaries. The role of urodynamics in the evaluation of urgency remains uncertain, with many trials showing limited benefit as a preoperative investigation. Fluid restriction and bladder retraining remain important first-line interventions. Many new anticholinergic medications have been licensed, with limited benefits compared with existing preparations. Intravesical botulinum toxin has become a popular alternative for patients who fail oral therapies.

SUMMARY

Although there have been few important therapeutic innovations, recent publications have led to greater sophistication in assessment methods and a clearer understanding of the role of existing interventions.