Dose response with darifenacin, a novel once-daily M3 selective receptor antagonist for the treatment of overactive bladder: results of a fixed dose study

Comparative assessment of efficacy and safety of approved oral therapies for overactive bladder: a systematic review and network meta-analysis

bladder based on a systematic review and network meta-analysis approach.

METHODS

Pubmed, Embase, Web of Science, and the Cochrane Register of Clinical Trials databases were systematically searched. The search time frame was from database creation to June 2, 2022. Randomized controlled double-blind trials of oral medication for overactive bladder were screened against the protocol's entry criteria. Trials were evaluated for quality using the Cochrane Risk of Bias Assessment Tool, and data were statistically analyzed using Stata 16.0 software.

RESULT

A total of 60 randomized controlled double-blind clinical trials were included involving 50,333 subjects. Solifenacin 10mg was the most effective in mean daily micturitions and incontinence episodes, solifenacin 5/10mg in mean daily urinary urgency episodes and nocturia episodes, fesoterodine 8mg in urgency incontinence episodes/d and oxybutynin 5mg in voided volume/micturition. In terms of safety, solifenacin 5mg, ER-tolterodine 4mg, mirabegron, vibegron and ER-oxybutynin 10mg all showed a better incidence of dry mouth, fesoterodine 4mg, ER-oxybutynin 10mg, tolterodine 2mg, and vibegron in the incidence of constipation. Compared to placebo, imidafenacin 0.1mg showed a significantly increased incidence in hypertension, solifenacin 10mg in urinary tract infection, fesoterodine 4/8mg and darifenacin 15mg in headache.

CONCLUSION

Solifenacin showed better efficacy. For safety, most anticholinergic drugs were more likely to cause dry mouth and constipation, lower doses were better tolerated. The choice of drugs should be tailored to the patient's specific situation to find the best balance between efficacy and safety.

Oral anticholinergic drugs versus placebo or no treatment for managing overactive bladder syndrome in adults

BACKGROUND

Around 16% of adults have symptoms of overactive bladder (OAB; urgency with frequency and/or urge incontinence), with prevalence increasing with age. Anticholinergic drugs are commonly used to treat this condition. This is an update of a Cochrane Review first published in 2002 and last updated in 2006.

OBJECTIVES

To assess the effects of anticholinergic drugs compared with placebo or no treatment for treating overactive bladder syndrome in adults.

SEARCH METHODS

We searched the Cochrane Incontinence Specialised Register, which contains trials identified from the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, MEDLINE In-Process, MEDLINE Epub Ahead of Print, ClinicalTrials.gov, WHO ICTRP and handsearching of journals and conference proceedings (searched 14 January 2020), and the reference lists of relevant articles. We updated this search on 3 May 2022, but these results have not yet been fully incorporated.

SELECTION CRITERIA

We included randomised or quasi-randomised trials in adults with overactive bladder syndrome that compared an anticholinergic drug alone with placebo treatment.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed eligibility and extracted data from the included studies, including an assessment of the risk of bias. We assessed the certainty of the body of evidence using the GRADE approach. We processed data as described in the Cochrane Handbook for Systematic Reviews of Interventions.

MAIN RESULTS

We included 104 studies, 71 of which were new or updated for this version of the review. Although 12 studies did not report the number of participants, there were 47,106 people in the remainder of the included studies. The majority of the studies had insufficient information to allow judgement of risk of bias and we judged them to be unclear for all domains. Nine anticholinergic drugs were included in these studies: darifenacin; fesoterodine; imidafenacin; oxybutynin; propantheline; propiverine; solifenacin; tolterodine and trospium. No studies were found that compared anticholinergic drugs to no treatment. At the end of the treatment period, anticholinergics may slightly increase condition-specific quality of life (mean difference (MD) 4.41 lower, 95% confidence interval (CI) 5.28 lower to 3.54 lower (scale range -100 to 0); 12 studies, 6804 participants; low-certainty evidence). Anticholinergics are probably better than placebo in terms of patient perception of cure or improvement (risk ratio (RR) 1.38, 95% CI 1.15 to 1.66; 9 studies, 8457 participants; moderate-certainty evidence), and the mean number of urgency episodes per 24-hour period (MD 0.85 lower, 95% CI 1.03 lower to 0.67 lower; 23 studies, 16,875 participants; moderate-certainty evidence). Compared to placebo, anticholinergics may result in an increase in dry mouth adverse events (RR 3.50, 95% CI 3.26 to 3.75; 66 studies, 38,368 participants; low-certainty evidence), and may result in an increased risk of urinary retention (RR 3.52, 95% CI 2.04 to 6.08; 17 studies, 7862 participants; low-certainty evidence). Taking anticholinergics may be more likely to lead to participants withdrawing from the studies due to adverse events (RR 1.37, 95% CI 1.21 to 1.56; 61 studies, 36,943 participants; low-certainty evidence). However, taking anticholinergics probably reduces the mean number of micturitions per 24-hour period compared to placebo (MD 0.85 lower, 95% CI 0.98 lower to 0.73 lower; 30 studies, 19,395 participants; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

The use of anticholinergic drugs by people with overactive bladder syndrome results in important but modest improvements in symptoms compared with placebo treatment. In addition, recent studies suggest that this is generally associated with only modest improvement in quality of life. Adverse effects were higher with all anticholinergics compared with placebo. Withdrawals due to adverse effects were also higher for all anticholinergics except tolterodine. It is not known whether any benefits of anticholinergics are sustained during long-term treatment or after treatment stops.

No. 283-Treatments for Overactive Bladder: Focus on Pharmacotherapy

OBJECTIVE

To provide guidelines for pharmacotherapy to treat overactive bladder syndrome (OAB).

OPTIONS

Pharmacotherapy for OAB includes anticholinergic (antimuscarinic) drugs and vaginal estrogen. Both oral and transdermal anticholinergic preparations are available.

OUTCOMES

To provide understanding of current available evidence concerning safety and clinical efficacy of pharmacotherapy for OAB; to guide selection of anticholinergic therapy based on individual patient characteristics.

EVIDENCE

The Cochrane Library and Medline were searched for articles published from 1950 to the present related to individual anticholinergic drugs. Review articles on management of refractory OAB were also examined. Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. There were no date or language restrictions. Searches were updated on a regular basis and incorporated in the guideline to 2010.

VALUES

The quality of evidence is rated and recommendations are made using the criteria described by the Canadian Task Force on Preventive Health Care (Table 1).

BENEFITS, HARMS, AND COSTS

Anticholinergics are the mainstay of pharmacotherapy for OAB. Evidence for their efficacy is mostly derived from short-term phase III randomized drug trials. Placebo response is strong, and long-term follow-up and patient subjective outcome data are lacking. Care providers need to be well acquainted with the side effects of anticholinergics and select therapy based on individual patient parameters.

RECOMMENDATIONS

Overactive bladder - 18 years - Part II

Traditionally, the treatment of overactive bladder syndrome has been based on the use of oral medications with the purpose of reestablishing the detrusor stability. The recent better understanding of the urothelial physiology fostered conceptual changes, and the oral anticholinergics - pillars of the overactive bladder pharmacotherapy - started to be not only recognized for their properties of inhibiting the detrusor contractile activity, but also their action on the bladder afference, and therefore, on the reduction of the symptoms that constitute the syndrome. Beta-adrenergic agonists, which were recently added to the list of drugs for the treatment of overactive bladder, still wait for a definitive positioning - as either a second-line therapy or an adjuvant to oral anticholinergics. Conservative treatment failure, whether due to unsatisfactory results or the presence of adverse side effects, define it as refractory overactive bladder. In this context, the intravesical injection of botulinum toxin type A emerged as an effective option for the existing gap between the primary measures and more complex procedures such as bladder augmentation. Sacral neuromodulation, described three decades ago, had its indication reinforced in this overactive bladder era. Likewise, the electric stimulation of the tibial nerve is now a minimally invasive alternative to treat those with refractory overactive bladder. The results of the systematic literature review on the oral pharmacological treatment and the treatment of refractory overactive bladder gave rise to this second part of the review article Overactive Bladder - 18 years, prepared during the 1st Latin-American Consultation on Overactive Bladder.

Treatments for overactive bladder: focus on pharmacotherapy

OBJECTIVE

To provide guidelines for pharmacotherapy to treat overactive bladder syndrome (OAB).

OPTIONS

Pharmacotherapy for OAB includes anticholinergic (antimuscarinic) drugs and vaginal estrogen. Both oral and transdermal anticholinergic preparations are available.

OUTCOMES

To provide understanding of current available evidence concerning safety and clinical efficacy of pharmacotherapy for OAB; to guide selection of anticholinergic therapy based on individual patient characteristics.

EVIDENCE

The Cochrane Library and Medline were searched for articles published from 1950 to the present related to individual anticholinergic drugs. Review articles on management of refractory OAB were also examined. Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. There were no date or language restrictions. Searches were updated on a regular basis and incorporated in the guideline to 2010.

VALUES

The quality of evidence is rated and recommendations are made using the criteria described by the Canadian Task Force on Preventive Health Care (Table 1).

BENEFITS, HARMS, AND COSTS

Anticholinergics are the mainstay of pharmacotherapy for OAB. EVIDENCE for their efficacy is mostly derived from short-term phase III randomized drug trials. Placebo response is strong, and long-term follow-up and patient subjective outcome data are lacking. Care providers need to be well acquainted with the side effects of anticholinergics and select therapy based on individual patient parameters. Recommendations 1. Behavioural management protocols and functional electrical stimulation should be offered in the spectrum of effective primary treatments for overactive bladder syndrome. (I-A) 2. Oral oxybutynin, immediate and extended release, as well as transdermal oxybutynin, may be offered as treatment for overactive bladder syndrome, as they are associated with significant objective clinical improvement at 12 weeks. (I-A) Oxybutynin immediate release has superior cost-effectiveness but more side effects than other anticholinergics. (I-A) Adverse events associated with transdermal oxybutynin are fewer than with oral oxybutynin. (I-A) 3. Tolterodine, immediate and extended release, may be offered as treatment for overactive bladder syndrome, as it is associated with significant objective clinical improvement at 12 weeks. (I-A) 4. Trospium, immediate and extended release, may be offered as treatment for overactive bladder syndrome as it is associated with significant clinical improvement at 12 weeks. (I-A) Trospium is an adequate anticholinergic choice for overactive bladder syndrome patients with pre-existing cognitive impairment (II-B) and for overactive bladder syndrome patients taking concurrent CYP450 inhibitors. (III-B) 5. Solifenacin may be offered as treatment for overactive bladder syndrome, as it is associated with significant objective clinical improvement at 12 weeks. (I-A) Solifenacin may be an adequate anticholinergic choice for elderly overactive bladder syndrome patients or patients with pre-existing cognitive dysfunction. (I-B) 6. Darifenacin may be offered as treatment for overactive bladder syndrome, as it is associated with significant objective clinical improvement at 12 weeks. (I-A) Darifenacin is an adequate anticholinergic choice for overactive bladder syndrome patients with pre-existing cardiac concerns or cognitive dysfunction. (I-B) 7. Overactive bladder syndrome patients should be offered a choice between bladder training, functional electric stimulation, and anticholinergic therapy, as there is no difference in cure rates. Combination therapy does not have a clear advantage over one therapy alone. (I-A) 8. The choice of anticholinergic therapy should be guided by individual patient comorbidities, as objective efficacy of anticholinergic drugs is similar. (I-A) Dose escalation does not improve objective parameters and causes more anticholinergic adverse effects. It is, however, associated with improved subjective outcomes. (I-A) To decrease side effects, switching to a lower dose or using an extended release formulation or a transdermal delivery mechanism should be considered. (I-A) 9. Education on treatment efficacy, realistic expectations, and length of treatment should be offered to patients upon initiation of anticholinergic therapy, as continuation rates for anticholinergic therapy are low. (III-B) 10. Oral or transdermal estrogen supplementation should not be recommended for treatment of overactive bladder syndrome as its effects are comparable to placebo. (I-E) Vaginal estrogen can be suggested for subjective improvements in overactive bladder syndrome symptoms. (III-B) 11. Intravesical botulinum toxin injection and sacral nerve and posterior tibial nerve stimulation are clinically effective options for patients with overactive bladder syndrome unresponsive to conservative options, anticholinergics, or vaginal estrogen. (I-A).

Efficacy and safety of fesoterodine 8 mg in subjects with overactive bladder after a suboptimal response to tolterodine ER

AIMS

To assess fesoterodine 8 mg efficacy over time and vs. placebo in subjects with overactive bladder (OAB) who responded suboptimally to tolterodine extended release (ER) 4 mg.

METHODS

In a 12-week, double-blind trial, subjects with self-reported OAB symptoms for ≥ 6 months, mean of ≥ 8 micturitions and ≥ 2 to < 15 urgency urinary incontinence (UUI) episodes/24 h, and suboptimal response to tolterodine ER 4 mg (defined as ≤ 50% reduction in UUI episodes during 2-week run-in) were randomised to fesoterodine (4 mg for 1 week, 8 mg for 11 weeks) or placebo once daily. Change from baseline to week 12 in UUI episodes (primary end-point) was analysed in step-wise fashion: first, baseline vs. week 12 for fesoterodine; if significant, then change from baseline to week 12 for fesoterodine vs. placebo.

RESULTS

By week 12, subjects receiving fesoterodine 8 mg had significantly greater improvement from baseline vs. placebo in UUI episodes, urgency episodes and scores on the Patient Perception of Bladder Control, Urgency Perception Scale and OAB Questionnaire Symptom Bother and Health-Related Quality of Life scales and domains (all p < 0.05). 50% and 70% UUI responder rates were also significantly higher with fesoterodine 8 mg vs. placebo at week 12 (p < 0.05). Dry mouth (placebo, 4%, 12/301; fesoterodine, 16.6%, 51/308) and constipation (placebo, 1.3%, 4/301; fesoterodine, 3.9%, 12/308) were the most frequent adverse events.

CONCLUSIONS

Subjects who responded suboptimally to tolterodine ER 4 mg showed significant improvements in UUI and other OAB symptoms and patient-reported outcomes, with good tolerability, during treatment with fesoterodine 8 mg vs. placebo.

Superiority of fesoterodine 8 mg vs 4 mg in reducing urgency urinary incontinence episodes in patients with overactive bladder: results of the randomised, double-blind, placebo-controlled EIGHT trial

OBJECTIVE

To assess the superiority of fesoterodine 8 mg vs 4 mg for improvement in urgency urinary incontinence (UUI) episodes and other diary variables, diary-dry rate (proportion of patients with >0 UUI episodes on baseline diary and 0 UUI episodes on post-baseline diary), and improvements in measures of symptom bother, health-related quality of life (HRQL), and other patient-reported outcomes (PROs).

PATIENTS AND METHODS

This was a 12-week, randomised, double-blind, placebo-controlled, multinational trial of men and women aged ≥18 years with overactive bladder (OAB) symptoms including UUI (ClinicalTrials.gov ID NCT01302067). Patients were randomised (2:2:1) to receive fesoterodine 8 mg, fesoterodine 4 mg, or placebo once daily; those randomised to fesoterodine 8 mg started with fesoterodine 4 mg once daily for 1 week, then 8 mg once daily for the remaining 11 weeks. Patients completed bladder diaries at baseline and weeks 4 and 12 and the Patient Perception of Bladder Condition (PPBC), Urgency Perception Scale (UPS), and Overactive Bladder Questionnaire (OAB-q) at baseline and week 12. The primary endpoint was change from baseline to week 12 in UUI episodes per 24 h.

RESULTS

At week 12, patients receiving fesoterodine 8 mg (779 patients) had significantly greater reductions from baseline in UUI episodes, micturitions, and urgency episodes than patients receiving fesoterodine 4 mg (790) or placebo (386); diary-dry rate was significantly higher in the fesoterodine 8-mg group vs the fesoterodine 4-mg and placebo groups (all P < 0.05). At week 12, patients receiving fesoterodine 8 mg also had significantly greater improvements in scores on the PPBC, UPS, and all OAB-q scales and domains than patients receiving fesoterodine 4 mg or placebo (all P < 0.01). Patients receiving fesoterodine 4 mg had significantly greater improvements in UUI episodes, urgency episodes, and micturitions; significantly higher diary-dry rates; and significantly greater improvement in PPBC scores and OAB-q scores than patients receiving placebo (all P < 0.05). Dry mouth was the most commonly reported adverse event (AE) in the fesoterodine groups (placebo group, 3.4%; fesoterodine 4-mg group, 12.9%; fesoterodine 8-mg group, 26.1%); most cases were mild or moderate in all treatment groups. Rates of serious AEs and discontinuations due to AEs were low in all groups.

CONCLUSIONS

In a 12-week, prospectively designed, superiority trial, fesoterodine 8 mg showed statistically significantly superior efficacy vs fesoterodine 4 mg and placebo, as measured by reductions in UUI episodes and other diary variables, diary-dry dry rate, and improvements in measures of symptom bother, HRQL, and other PROs; clear evidence of dose-dependent efficacy is unique to fesoterodine among antimuscarinics and other oral agents for the treatment of OAB. Fesoterodine 4 mg was significantly more effective than placebo on all outcomes except for improvements in UPS scores. These data support the benefit of having two doses of fesoterodine in clinical practice, with the recommended starting dose of 4 mg for all patients and the fesoterodine 8-mg dose available for patients who require a higher dose to achieve optimal symptom relief.

Comparative efficacy and safety of medical treatments for the management of overactive bladder: a systematic literature review and mixed treatment comparison

CONTEXT

Overactive bladder (OAB) treatment guidelines recommend antimuscarinics as first-line pharmacologic therapy. Mirabegron is a first-in-class β3-adrenoceptor agonist licensed for the treatment of OAB and has shown to be well tolerated and effective in the treatment of OAB symptoms.

OBJECTIVE

To assess the relative efficacy and tolerability of OAB medications, specifically mirabegron 50 mg versus antimuscarinics in patients with OAB.

EVIDENCE ACQUISITION

A systematic literature search was performed on published peer-reviewed articles from 2000 to 2013. This review included randomised controlled trials (RCTs) studying changes in symptoms (micturition frequency, incontinence, and urgency urinary incontinence [UUI] episodes) and incidence of the most frequently reported adverse events (dry mouth, constipation) associated with current OAB medications. The following drugs were considered in addition to mirabegron: darifenacin, tolterodine immediate release (IR) and extended release (ER), oxybutynin IR/ER, trospium, solifenacin, and fesoterodine. Bayesian mixed treatment comparisons (MTCs) were performed for efficacy (micturition, incontinence, UUI) and tolerability (dry mouth, constipation, blurred vision).

EVIDENCE SYNTHESIS

Overall, 44 RCTs involving 27,309 patients were included. The MTCs showed that mirabegron 50 mg was as efficacious as antimuscarinics in reducing the frequency of micturition incontinence and UUI episodes, with the exception of solifenacin 10 mg that was more efficacious than mirabegron 50 mg in improving micturition frequency and frequency of UUI. Mirabegron 50 mg had an incidence of dry mouth similar to placebo and significantly lower than all included antimuscarinics.

CONCLUSIONS

Mirabegron 50 mg had similar efficacy to most antimuscarinics and lower incidence of dry mouth, the most common adverse event reported with antimuscarinics and one of the main causes of discontinuation of treatment. Despite being a powerful tool for evidence-based health care evaluation, the Bayesian MTC method has limitations. Further head-to-head comparisons between mirabegron and antimuscarinics should be conducted to confirm our results.

A review and additional post-hoc analyses of the incidence and impact of constipation observed in darifenacin clinical trials

Background

Constipation is a common side effect of antimuscarinic treatment for overactive bladder (OAB). This review evaluates the incidence and impact of constipation on the lives of patients with OAB being treated with darifenacin.

Methods

Constipation data from published Phase III and Phase IIIb/IV darifenacin studies were reviewed and analyzed. Over 4000 patients with OAB (aged 18–89 years; ≥80% female) enrolled in nine studies (three Phase III [data from these fixed-dose studies were pooled and provide the primary focus for this review], three Phase IIIb, and three Phase IV). The impact of constipation was assessed by discontinuations, use of concomitant laxatives, patient-reported perception of treatment, and a bowel habit questionnaire.

Results

In the pooled Phase III trials, 14.8% (50/337) of patients on darifenacin 7.5 mg/day and 21.3% (71/334) on 15 mg/day experienced constipation compared with 12.6% (28/223) and 6.2% (24/388) with tolterodine and placebo, respectively. In addition, a few patients discontinued treatment due to constipation (0.6% [2/337], 1.2% [4/334], 1.8% [4/223], and 0.3% [1/388] in the darifenacin 7.5 mg/day or 15 mg/day, tolterodine, and placebo groups, respectively), or required concomitant laxatives (3.3% [11/337], 6.6% [22/334], 7.2% [16/223], and 1.5% [6/388] in the darifenacin 7.5 mg/day or 15 mg/day, tolterodine, and placebo groups, respectively). Patient-reported perception of treatment quality was observed to be similar between patients who experienced constipation and those who did not. During the long-term extension study, a bowel habit questionnaire showed only small numerical changes over time in frequency of bowel movements, straining to empty bowels, or number of days with hard stools.

Conclusion

While constipation associated with darifenacin was reported in ≤21% of the patient population, it only led to concomitant laxative use in approximately one-third of these patients and a low incidence of treatment discontinuation. These data suggest that constipation did not impact patient perception of treatment quality.

Efficacy and adverse events of antimuscarinics for treating overactive bladder: network meta-analyses

CONTEXT

Millions of people worldwide experience overactive bladder (OAB), and antimuscarinics are the pharmacologic treatment of choice. Several conventional meta-analyses have been published, but they fail to quantify efficacy and adverse events across drugs, dosages, formulations, and pharmaceutical forms.

OBJECTIVE

To perform two network meta-analyses summarizing the efficacy and adverse events of antimuscarinics in the treatment of OAB.

EVIDENCE ACQUISITION

Medline and Scopus searches, previous systematic reviews, conference abstracts, book chapters, and the reference lists of relevant articles were searched. Trialists were contacted. Eligible studies were randomized trials that compared at least one antimuscarinic for treating OAB with placebo or with another antimuscarinic, and that reported efficacy and/or adverse event outcomes. Efficacy was assessed for six outcomes (perception of cure or improvement, urgency episodes per 24h, leakage episodes per 24h, urgency incontinence episodes per 24h, micturitions per 24h, and nocturia episodes per 24h). Adverse events were assessed in seven categories according to the Common Terminology Criteria for Adverse Events. Across all outcomes, a summary efficacy and an adverse event score were computed. Two authors independently extracted data.

EVIDENCE SYNTHESIS

For the comparison of the efficacy, 76 trials enrolling 38 662 patients were included; for adverse events, 90 trials enrolling 39 919 patients were included. In the subset of studies reporting on treatments and dosages as used in clinical practice, 40 mg/d trospium chloride, 100mg/g per day oxybutynin topical gel, and 4 mg/d fesoterodine had the best efficacy, while higher dosages of orally administered oxybutynin and propiverine had the least favorable relationship of efficacy and adverse events.

CONCLUSIONS

This is the first study allowing trade-offs between efficacy and adverse events of various drugs and dosages in the treatment of patients with OAB. Differences among the various antimuscarinics call for careful, patient-centered management in which regimen changes should be considered.

Muscarinic agonists and antagonists: effects on the urinary bladder

Voiding of the bladder is the result of a parasympathetic muscarinic receptor activation of the detrusor smooth muscle. However, the maintenance of continence and a normal bladder micturition cycle involves a complex interaction of cholinergic, adrenergic, nitrergic and peptidergic systems that is currently little understood. The cholinergic component of bladder control involves two systems, acetylcholine (ACh) released from parasympathetic nerves and ACh from non-neuronal cells within the urothelium. The actions of ACh on the bladder depend on the presence of muscarinic receptors that are located on the detrusor smooth muscle, where they cause direct (M₃) and indirect (M₂) contraction; pre-junctional nerve terminals where they increase (M₁) or decrease (M₄) the release of ACh and noradrenaline (NA); sensory nerves where they influence afferent nerve activity; umbrella cells in the urothelium where they stimulate the release of ATP and NO; suburothelial interstitial cells with unknown function; and finally, other unidentified sites in the urothelium from where prostaglandins and inhibitory/relaxatory factors are released. Thus, the actions of muscarinic receptor agonists and antagonists on the bladder may be very complex even when considering only local muscarinic actions. Clinically, muscarinic antagonists remain the mainstay of treatment for the overactive bladder (OAB), while muscarinic agonists have been used to treat hypoactive bladder. The antagonists are effective in treating OAB, but their precise mechanisms and sites of action (detrusor, urothelium, and nerves) have yet to be established. Potentially more selective agents may be developed when the cholinergic systems within the bladder are more fully understood.

Which anticholinergic drug for overactive bladder symptoms in adults

BACKGROUND

Around 16% to 45% of adults have overactive bladder symptoms (urgency with frequency and/or urge incontinence - 'overactive bladder syndrome'). Anticholinergic drugs are common treatments.

OBJECTIVES

To compare the effects of different anticholinergic drugs for overactive bladder symptoms.

SEARCH METHODS

We searched the Cochrane Incontinence Group Specialised Trials Register (searched 8 March 2011) and reference lists of relevant articles.

SELECTION CRITERIA

Randomised trials in adults with overactive bladder symptoms or detrusor overactivity that compared one anticholinergic drug with another, or two doses of the same drug.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed eligibility, trial quality and extracted data. Data were processed as described in the Cochrane Reviewers' Handbook.

MAIN RESULTS

Eighty six trials, 70 parallel and 16 cross-over designs were included (31,249 adults). Most trials were described as double-blind, but were variable in other aspects of quality. Crossover studies did not present data in a way that could be included in the meta-analyses. Twenty nine collected quality of life data (the primary outcome measure) using validated measures, but only fifteen reported useable data.Tolterodine versus oxybutynin: There were no statistically significant differences for quality of life, patient reported cure or improvement, leakage episodes or voids in 24 hours, but fewer withdrawals due to adverse events with tolterodine (Risk Ratio (RR) 0.52, 95% confidence interval (CI) 0.40 to 0.66, data from eight trials), and less risk of dry mouth (RR 0.65, 95% CI 0.60 to 0.71, data from ten trials).Solifenacin versus tolterodine: There were statistically significant differences for quality of life (standardised mean difference (SMD) -0.12, 95% CI -0.23 to -0.01, data from three trials), patient reported cure/improvement (RR 1.25, 95% CI 1.13 to 1.39, data from two trials), leakage episodes in 24 hours (weighted mean difference (WMD) -0.30, 95% CI -0.53 to -0.08, data from four studies) and urgency episodes in 24 hours (WMD -0.43, 95% CI -0.74 to -0.13, data from four trials), all favouring solifenacin. There was no difference in withdrawals due to adverse events and dry mouth, but after sensitivity analysis the dry mouth (RR 0.69, 95% CI 0.51 to 0.94) was statistically significantly lower with solifenacin when compared to Immediate Release (IR) tolterodine.Fesoterodine versus extended release tolterodine: Three trials contributed to the meta analyses. There were statistically significant differences for quality of life (SMD -0.20, 95% CI -0.27 to -0.14), patient reported cure/improvement (RR 1.11, 95% CI 1.06 to 1.16), leakage episodes (WMD -0.19, 95% CI -0.30 to -0.09), frequency (WMD -0.27, 95% CI -0.47 to -0.06) and urgency episodes (WMD -0.44, 95% CI -0.72 to -0.16) in 24 hours, all favouring fesoterodine, but those taking fesoterodine had higher risk of withdrawal due to adverse events (RR 1.45, 95% CI 1.07 to 1.98) and higher risk of dry mouth (RR 1.80, 95% CI 1.58 to 2.05) at 12 weeks.Different doses of tolterodine: The standard recommended starting dose (2 mg twice daily) was compared with two lower (0.5 mg and 1 mg twice daily), and one higher dose (4 mg twice daily). The effects of 1 mg, 2 mg and 4 mg doses were similar for leakage episodes and micturitions in 24 hours, with greater risk of dry mouth with 2 and 4 mg doses at two to 12 weeks.Different doses of solifenacin: The standard recommended starting dose of 5 mg once daily was compared to 10 mg: while frequency and urgency were less (better) with 10 mg compared to 5 mg, there was a higher risk of dry mouth with 10 mg solifenacin at four to 12 weeks.Different doses of fesoterodine:The recommended starting dose of 4mg once daily was compared to 8 and 12 mg. The clinical efficacy (patient reported cure, leakage episodes, micturition per 24 hours) of 8 mg was better than 4 mg fesoterodine but with a higher risk of dry mouth with 8 mg.There was no statistically significant difference between 4 and 12 mg in the efficacy but the dry mouth was significantly higher with 12 mg at eight to 12 weeks.Extended versus immediate release preparations of oxybutynin and/or tolterodine: There were no statistically significant differences for cure/improvement, leakage episodes or micturitions in 24 hours, or withdrawals due to adverse events, but there were few data. Overall, extended release preparations had less risk of dry mouth at two to 12 weeks.One extended release preparation versus another: There was less risk of dry mouth with oral extended release tolterodine than oxybutynin (RR 0.75, 95% CI 0.59 to 0.95), but no difference between transdermal oxybutynin and oral extended release tolterodine although some people withdrew due to skin reaction at the transdermal patch site at 12 weeks.

AUTHORS' CONCLUSIONS

Where the prescribing choice is between oral immediate release oxybutynin or tolterodine, tolterodine might be preferred for reduced risk of dry mouth. With tolterodine, 2 mg twice daily is the usual starting dose, but a 1 mg twice daily dose might be equally effective, with less risk of dry mouth. If extended release preparations of oxybutynin or tolterodine are available, these might be preferred to immediate release preparations because there is less risk of dry mouth.Between solifenacin and immediate release tolterodine, solifenacin might be preferred for better efficacy and less risk of dry mouth. Solifenacin 5 mg once daily is the usual starting dose, this could be increased to 10 mg once daily for better efficacy but with increased risk of dry mouth.Between fesoterodine and extended release tolterodine, fesoterodine might be preferred for superior efficacy but has higher risk of withdrawal due to adverse events and higher risk of dry mouth.There is little or no evidence available about quality of life, costs, or long-term outcome in these studies. There were insufficient data from trials of other anticholinergic drugs to draw any conclusions.

Persistence and adherence in the treatment of overactive bladder syndrome with anticholinergic therapy: a systematic review of the literature

Overactive bladder syndrome (OAB) is a chronic condition that has an impact on patients' daily activities and health-related quality of life (HRQL). Anticholinergic therapy is often prescribed following insufficient results with behaviour modification alone; however, rates of treatment discontinuation are consistently high. This study systematically reviewed persistence and adherence data in patients with OAB treated with anticholinergic therapy. A search focused on the intersection of OAB, persistence/adherence, and anticholinergic therapy was conducted in MEDLINE and EMBASE. Articles published after 1998 were reviewed and selected for inclusion based on prespecified criteria. A total of 147 articles and two abstracts were included in the review. Results from 12-week clinical trials showed high rates of discontinuation, ranging from 4% to 31% and 5% to 20% in treatment and placebo groups, respectively. Unsurprisingly, rates of discontinuation found in medical claims studies were substantially higher, with 43% to 83% of patients discontinuing medication within the first 30 days and rates continuing to rise over time. Findings from medical claims studies also suggest that over half of patients never refill their initial prescription and that adherence levels tend to be low, with mean/median medication possession ratio (MPR) values ranging from 0.30 to 0.83. The low levels of persistence and adherence documented in this review reveal cause for concern about the balance between the efficacy and tolerability of anticholinergic agents. Strategies should be identified to increase persistence and adherence. New agents and non-pharmacologic alternatives with good efficacy and minimal side effects should be explored.

Adverse event assessment of antimuscarinics for treating overactive bladder: a network meta-analytic approach

Background

Overactive bladder (OAB) affects the lives of millions of people worldwide and antimuscarinics are the pharmacological treatment of choice. Meta-analyses of all currently used antimuscarinics for treating OAB found similar efficacy, making the choice dependent on their adverse event profiles. However, conventional meta-analyses often fail to quantify and compare adverse events across different drugs, dosages, formulations, and routes of administration. In addition, the assessment of the broad variety of adverse events is dissatisfying. Our aim was to compare adverse events of antimuscarinics using a network meta-analytic approach that overcomes shortcomings of conventional analyses.

Methods

Cochrane Incontinence Group Specialized Trials Register, previous systematic reviews, conference abstracts, book chapters, and reference lists of relevant articles were searched. Eligible studies included randomized controlled trials comparing at least one antimuscarinic for treating OAB with placebo or with another antimuscarinic, and adverse events as outcome measures. Two authors independently extracted data. A network meta-analytic approach was applied allowing for joint assessment of all adverse events of all currently used antimuscarinics while fully maintaining randomization.

Results

69 trials enrolling 26′229 patients were included. Similar overall adverse event profiles were found for darifenacin, fesoterodine, transdermal oxybutynin, propiverine, solifenacin, tolterodine, and trospium chloride but not for oxybutynin orally administered when currently used starting dosages were compared.

Conclusions

The proposed generally applicable transparent network meta-analytic approach summarizes adverse events in an easy to grasp way allowing straightforward benchmarking of antimuscarinics for treating OAB in clinical practice. Most currently used antimuscarinics seem to be equivalent first choice drugs to start the treatment of OAB except for oral oxybutynin dosages of ≥10 mg/d which may have more unfavorable adverse event profiles.

Overactive bladder drugs and constipation: a meta-analysis of randomized, placebo-controlled trials

BACKGROUND

Anticholinergic drugs are commonly prescribed for symptomatic treatment of overactive bladder (OAB). While recent meta-analyses have characterized the prevalence of dry mouth among patients utilizing OAB medications, prevalence of constipation has not been systematically reviewed.

AIMS

To provide an effect measure for constipation associated with anticholinergic OAB drugs versus placebo.

METHODS

A meta-analysis of trials with darifenacin, fesoterodine, oxybutynin, solifenacin, tolterodine, and trospium was conducted. All randomized, placebo-controlled studies of anticholinergic OAB drugs published in English language and identified in Medline and Cochrane databases were considered for inclusion in this meta-analysis. Those meeting predetermined design characteristics and having sufficient duration (≥2 weeks) were included. Constipation-related data from all included studies were abstracted.

RESULTS

One hundred two English-language, randomized, placebo-controlled trials were originally identified. Thirty-seven studies were ultimately included in the analysis, involving 19,434 total subjects (12,368 treatment+7,066 placebo patients). The odds ratios for constipation compared with placebo were as follows: overall [odds ratio (OR) 2.18, 95% confidence interval (CI)=1.82-2.60], tolterodine (OR 1.36, 95% CI=1.01-1.85), darifenacin (OR 1.93, 95% CI=1.40-2.66), fesoterodine (OR 2.07, 95% CI=1.28-3.35), oxybutynin (OR 2.34, 95% CI=1.31-4.16), trospium (OR 2.93, 95% CI=2.00-4.28), and solifenacin (OR 3.02, 95% CI=2.37-3.84).

CONCLUSIONS

Our results demonstrate that patients prescribed anticholinergic OAB drugs are significantly more likely to experience constipation. Differences in muscarinic receptor affinities among individual agents may possibly account for the modest variation in constipation rates observed; however, such a determination warrants additional research.

Patient-optimized doses of fesoterodine improve bladder symptoms in an open-label, flexible-dose study

OBJECTIVE

To assess changes in overactive bladder (OAB) symptoms and patient-reported outcomes in a post hoc analysis in which subjects from a 12-week, open-label, flexible-dose fesoterodine study were stratified according to whether they opted for dose escalation.

PATIENTS AND METHODS

Subjects with OAB (eight or more micturitions and three or more urgency episodes per 24 h) who reported dissatisfaction with tolterodine within 2 years of screening received fesoterodine 4 mg once daily for 4 weeks, with an optional dose increase to 8 mg after week 4 based on discussion of efficacy and tolerability between the subject and investigator. Subjects completed 5-day diaries, the Patient Perception of Bladder Condition (PPBC) and Urgency Perception Scale (UPS) at baseline and weeks 4 and 12, and the Overactive Bladder Questionnaire (OAB-q) at baseline and week 12. Subjects rated treatment satisfaction at week 12.

RESULTS

Dose escalation to 8 mg at week 4 was chosen by 255 (50%) of 513 subjects. At baseline, subjects who opted for dose escalation at week 4 (escalators) had significantly higher means for all diary variables except urgency urinary incontinence (UUI) episodes, significantly greater OAB-q Symptom Bother scores and significantly lower OAB-q health-related quality of life (HRQL) scores (all P < 0.05) compared to subjects who did not opt for dose escalation (non-escalators). There was no significant difference in the percentage of escalators (51%) and non-escalators (48%) who reported at least one UUI episode on baseline diary. At week 4 (before the decision to escalate was made), all outcomes were significantly improved vs baseline among both groups (all P < 0.0001), although non-escalators had significantly greater improvements in all diary variables and in PPBC and UPS scores than escalators (all P < 0.05), and the 5-day diary-dry rate (i.e. the percentage of subjects with at least one UUI episode on baseline diary and no UUI episodes on week 4 diary) was significantly higher (P = 0.0016) among non-escalators (62%) than among escalators (42%). At week 12, all outcomes were again significantly improved vs baseline among both groups (all P < 0.0001). There were no significant differences between non-escalators and escalators in week 12 improvements for most diary variables, UPS scores, OAB-q Symptom Bother scores, the diary-dry rate (68% vs 60%) or the percentage of subjects who reported treatment satisfaction (82% vs 78%). However, escalators still had significantly greater improvements from baseline in urgency episodes, PPBC scores and OAB-q total HRQL and Coping domains (P < 0.05). Adverse event rates were similar between non-escalators and escalators. Dry mouth was the most frequently reported adverse event; most cases were mild.

CONCLUSION

Flexible-dose fesoterodine significantly improved OAB symptoms and patient-reported outcomes in subjects who chose to remain on the initial 4-mg dose, as well as in the 50% of subjects who escalated to the 8-mg dose after 4 weeks. Non-escalators had significantly fewer OAB symptoms at baseline and significantly greater improvements than escalators before dose escalation. Escalators showed increased symptom relief after dose escalation; improvements in most outcomes were similar among non-escalators and escalators by week 12. Flexible-dose fesoterodine was well tolerated, with similar adverse-event profiles observed in the escalator and non-escalator groups. These results may help clinicians to identify patients more likely to require fesoterodine 8 mg to achieve maximum relief of OAB symptoms and thus facilitate dose escalation in these patients.

The effect of nocturia on sleep

Sleep plays a vital role in physical and mental functioning. It is increasingly recognized that disturbed sleep is a highly prevalent and chronic condition that merits greater awareness due to the wide-ranging and serious repercussions associated with it. Nocturia is one of the causes of sleep disturbance and has been shown to impair functioning, quality of life, health and productivity, with those experiencing two or more voids per night reporting significant 'bother'. Nocturia warrants full consideration as a significant target for intervention, aiming to reduce the burden of disturbed sleep on individuals, families and society. Currently, however, a definitive evaluation of the most relevant sleep endpoints in nocturia therapy is lacking. One endpoint often used is the duration of the initial sleep period, which when evaluated in combination with the number of voiding episodes per night, might be an indication of the severity of sleep disruption in patients with nocturia.

Role of fesoterodine in the treatment of overactive bladder

Muscarinic receptors have long been the target receptors for treatment of patients with overactive bladder (OAB). These patients experience symptoms of urgency, urinary frequency and nocturia, with or without urge incontinence (the involuntary leakage of urine associated with urge). Fesoterodine, a pro-drug, structurally and functionally related to tolterodine, is the newest agent developed for the treatment of OAB. Fesoterodine is broken down to the active metabolite, 5-hydroxy-methyl-tolterodine (5-HMT) by non-specific esterases. This metabolism results in the complete breakdown of the parent compound and is responsible for dose related improvements in clinical efficacy and health related quality of life. Like other antimuscarinic agents including tolterodine, fesoterodine is associated with improvements in clinical variables related both to bladder filling (decreasing micturition frequency and increasing mean voided volume) and urgency (urgency and urge incontinence episodes). Improvements in health related quality of life following treatment with fesoterodine is indicated by improvements in 7 of the 9 variables measured by the King’s Health Questionnaire. Also like other antimuscarinic agents, fesoterodine use is associated with adverse events including dry mouth. However the incidence of dry mouth is reduced with fesoterodine, compared to oxybutynin, due to the improved bladder selectivity of 5-HMT.

Fesoterodine for the treatment of urinary incontinence and overactive bladder

Overactive bladder (OAB) is a highly prevalent condition, affecting males and females. The prevalence increases with age. Behavioral therapy and antimuscarinic therapy remain the first-line therapies for management of OAB. Despite improvements in symptoms, persistence with antimuscarinic therapy has remained low. Multiple factors including patient expectations, adverse effects and cost may affect persistence. Fesoterodine is one of the newest antimuscarinic agent approved for the management of OAB. It is unique in that it shares the same active metabolite as tolterodine, 5-hydoxymethyltolterodine (5-HMT); however, this conversion is established via ubiquitous esterases and not via the cytochrome P450 system, thus providing a faster and more efficient conversion to 5-HMT. Fesoterodine is available in 2 doses, 4 mg and 8 mg. Clinical trials have established a dose response relationship in efficacy parameters as well as improvements in quality of life. As with all antimuscarinics, dry mouth and constipation are the more common side effects. A combination of medical therapy and behavioral therapy improves the overall outcome in management of OAB. Dose flexibility may help improve efficacy outcomes and patient education on the management of common adverse effects may improve tolerability with these agents.

Nocturia and disturbed sleep in the elderly

BACKGROUND

Nocturnal urination (nocturia) is such a commonplace occurrence in the lives of many older adults that it is frequently overlooked as a potential cause of sleep disturbance.

METHODS

We examined the prevalence of nocturia and examined its role in self-reported insomnia and poor sleep quality in a survey of 1424 elderly individuals, ages 55-84. Data were derived from a 2003 National Sleep Foundation telephone poll conducted in a representative sample of the United States population who underwent a 20-min structured telephone interview. Nocturia was not a focus of the survey, but data collected relevant to this topic allowed examination of relevant associations with sleep.

RESULTS

When inquired about in a checklist format, nocturia was listed as a self-perceived cause of nocturnal sleep "every night or almost every night" by 53% of the sample, which was over four times as frequently as the next most often cited cause of poor sleep, pain (12%). In multivariate logistic models, nocturia was an independent predictor both of self-reported insomnia (75% increased risk) and reduced sleep quality (71% increased risk), along with female gender and other medical and psychiatric conditions.

CONCLUSIONS

Nocturia is a frequently overlooked cause of poor sleep in the elderly and may warrant targeted interventions.

Differential Pharmacological Effects of Antimuscarinic Drugs on Heart Rate: A Randomized, Placebo-controlled, Double-blind, Crossover Study With Tolterodine and Darifenacin in Healthy Participants ≥50 Years

Antimuscarinics, used commonly to treat overactive bladder, may differ in their potential to increase heart rate via effects on cardiac muscarinic M2 receptors. This prospective, 3-way crossover, randomized, double-blind study assessed the heart rate effects of 7 days' exposure to a nonselective M2/M3 receptor blocker (tolterodine; 4 mg/d), a highly selective M3 receptor blocker (darifenacin; 15 mg/d), and placebo in 162 healthy participants ≥50 years. Heart rate was measured by 24-hour Holter monitoring. Tolterodine significantly increased heart rate versus darifenacin and heart rate versus placebo, while darifenacin did not affect heart rate versus placebo. The proportion of participants with an increase in mean heart rate per 24 hours of ≥5 beats per minute was higher with tolterodine than with darifenacin (P = .0004) or with placebo (P = .0114) but did not differ between darifenacin and placebo. The results show that antimuscarinics exert differential effects on heart rate depending on their muscarinic receptor profile. This should be considered when selecting a treatment.

A systematic review and meta-analysis of randomized controlled trials with antimuscarinic drugs for overactive bladder

CONTEXT

Anticholinergic drugs are commonly used in patients with overactive bladder (OAB) who do not achieve symptom relief and quality of life improvement with conservative management. Several drugs, with different doses, formulations, and routes of administration are currently available, making the choice quite difficult.

OBJECTIVE

To evaluate efficacy and safety of different doses, formulations, and route of administration of the available anticholinergic drugs.

EVIDENCE ACQUISITION

A systematic review of the literature was performed in August 2007 using Medline, Embase, and Web of Science. Efficacy (micturitions per 24h, volume voided per micturition, urgency urinary incontinence episodes per 24h, incontinence episodes per 24h) and safety (mainly, adverse events and withdrawal rates) end points were evaluated in the randomized control trials (RCTs) assessing the role of anticholinergic drugs in non-neurogenic OAB. Meta-analysis of RCTs was conducted using the Review Manager software 4.2 (Cochrane Collaboration).

EVIDENCE SYNTHESIS

Our systematic search identified 50 RCTs and three pooled analyses. Tolterodine immediate release (IR) had a more favorable profile of adverse events than oxybutynin IR. Regarding different dosages of IR formulations, dose escalation might yield some limited improvements in the efficacy but at the cost of significant increase in the rate of adverse events. In the comparisons between IR and extended-release (ER) formulations, the latter showed some advantages, both in terms of efficacy and safety. With regard to the route of administration, use if a transdermal route of administration does not provide significant advantage over an oral one.

CONCLUSION

Many of the available RCTs have good methodological quality. ER formulations should be preferred to the IR ones. With regard to IR formulations, dose escalation might yield some improvements in the efficacy with significant increase in the AE. More clinical studies are needed to indicate which of the drugs should be used as first-, second-, or third-line treatment.

Developments in the pharmacotherapy of the overactive bladder

PURPOSE OF REVIEW

The overactive bladder is a common and distressing condition that has a significant impact on the quality of life of many people worldwide. Anticholinergics remain the first line in pharmacotherapy, however the use of these agents is hindered by adverse effects and limited efficacy. Thus there is a need for more effective treatments. Recently, there has been a move towards targeting novel pathways thought to play a role in overactivity. This review aims to provide an insight into the recent developments in pharmacotherapy of the overactive bladder.

RECENT FINDINGS

With recent advances in our understanding of the basic science of the overactive bladder it is becoming clear that the control of bladder functioning is far more complex than previously believed. Peripherally, a prominent role has emerged for the urothelium and the underlying suburothelium in mechanosensory control, and the role of afferent pathways in pathophysiology is increasingly recognized.

SUMMARY

Recent research has highlighted several potential targets for treatment of the overactive bladder, particularly within the mechanosensory pathways. With the exception of botulinum toxin, however, few new therapies have emerged showing clinical benefits. A clearer understanding of the pathophysiology of the bladder will hopefully lead to more effective and tolerated treatments.

Darifenacin: a muscarinic M3-selective receptor antagonist for the treatment of overactive bladder

Darifenacin is a novel, muscarinic M(3)-selective receptor antagonist with up to 59-fold selectivity for M(3) receptors compared with other muscarinic receptor subtypes and a low relative affinity for M(1) and M(2) receptors. This profile may explain its clinical efficacy in overactive bladder (OAB), the observed absence of adverse effects on cognitive function and reduced cardiovascular risks. Large-scale clinical trials have confirmed that darifenacin 7.5 and 15 mg/day provide rapid and meaningful improvement across a range of OAB symptoms, but with CNS and cardiac adverse event rates comparable to placebo. On this basis, darifenacin seems to meet the standard for an effective OAB pharmacotherapy that is well-tolerated and, more importantly, minimises the risk of safety-related adverse effects.

Nocturnal polyuria and nocturia relief in patients treated with solifenacin for overactive bladder symptoms

The objectives of this study are to determine whether patients with overactive bladder (OAB) and nocturia achieved relief of their nighttime voiding symptoms when treated with solifenacin and whether having nocturnal polyuria (NP) affected that response. The patients pooled from four phase III clinical trials were evaluated for reductions in nocturia episodes after treatment with solifenacin (5 or 10 mg) or placebo. A second analysis was performed in patients with and without NP. The patients treated with solifenacin experienced statistically significant reductions in nocturia episodes; median reductions were -35.5% for 5 mg of solifenacin and -36.4% for 10 mg of solifenacin compared with -25.0% for placebo, and significantly more patients treated with solifenacin vs placebo achieved a mean nocturic frequency of <or=1 episode/night. Solifenacin significantly reduced nocturia episodes only in patients without NP (mean change was -0.61 episodes/night for both doses compared with -0.43 episodes for placebo). Solifenacin significantly improved nocturia symptoms only in OAB patients without NP.

The clinical pharmacokinetics of darifenacin

Darifenacin hydrobromide is a selective muscarinic M(3) receptor antagonist that is indicated for use in treatment of overactive bladder disorder. Darifenacin was found to have a short terminal elimination half-life after intravenous and immediate-release oral dosage forms (3-4 hours) but this increased with a prolonged-release (PR) formulation (14-16 hours). The absolute bioavailability of darifenacin from 7.5 and 15 mg PR tablets was estimated to be 15.4% and 18.6%, respectively. With repeated once-daily oral administration of the PR formulation, peak plasma concentrations of darifenacin are achieved approximately 7 hours post-dose. After oral administration, darifenacin is well absorbed from the gastrointestinal tract and very little unchanged drug (<2%) is recovered in the faeces. Steady state is achieved after 6 days of once-daily administration of the PR formulation. As expected, values of peak plasma concentration (C(max)) and area under the plasma concentration-time curve are dose dependent, although the increase in plasma concentrations is proportionally greater than the increase in dose owing to saturation of presystemic metabolism. From intravenous administration, it has been established that darifenacin possesses a moderate-to-high hepatic extraction ratio, with high plasma clearance (36-52 L/h) and a volume of distribution (165-276L) that exceeds total body water. It is highly protein bound (98%), primarily to alpha(1)-acid glycoprotein. Darifenacin is subject to extensive hepatic metabolism, with 3% of unchanged drug excreted in urine and faeces. Metabolism is mediated by hepatic cytochrome P450 2D6 and 3A4, the main metabolic routes being monohydroxylation in the dihydrobenzfuran ring, dihydrobenzfuran ring opening, and N-dealkylation of the pyrrolidine nitrogen. Several possibly important drug-drug interactions have been identified with darifenacin, including ketoconazole, erythromycin and fluconazole, each of which increases darifenacin mean C(max) by 9.52-, 2.28- and 1.88-fold, respectively. When given with imipramine, darifenacin causes 1.6-fold higher plasma concentrations of the antidepressant and its major metabolite. Moderate hepatic impairment, but not renal insufficiency, has been shown to increase plasma concentrations of the drug. The pharmacokinetic profile of darifenacin is not affected by food.