Multiple dose pharmacokinetics of a new once daily extended release tolterodine formulation versus immediate release tolterodine

Intravaginal Tolterodine Formulation Intended for Overactive Bladder Treatment-Results of a Pharmacokinetic Phase I Pilot Study in Healthy, Postmenopausal Women

The aim was to assess the pharmacokinetics of tolterodine released from vaginal rings and of its active metabolite 5-hydroxymethyl tolterodine (5-HMT) compared to the respective pharmacokinetics resulting from oral administration of extended-release tolterodine in healthy, postmenopausal women. In this single-center, open-label trial, subjects received 4 treatments in a fixed sequence: fasted oral extended-release tolterodine 2.74 mg/d (reference, 5 days), single vaginal rings; tolterodine releasing rates: 0.95 mg/d (test 1, 13 days), 1.40 mg/d (test 2, 28 days), 1.90 mg/d (test 3, 28 days). Systemic exposure of tolterodine, 5-HMT, and the molar sum of unbound tolterodine/5-HMT (active moiety [AM]) in steady state was determined. Sixteen of 18 included women completed the study. For the oral formulation, peak-trough fluctuations of tolterodine, 5-HMT, and AM plasma concentrations (AM: mean maximum/minimum concentration, 2580/574 pmol/L = 4.5) were large. Intravaginal application led to steadier plasma concentrations (AM, test 3: mean maximum/minimum concentration, 1880/814 pmol/L = 2.3; fluctuation due to initial peak), which is the result of constant releasing rates after ring insertion over the 28-day application period. The vaginal rings demonstrated a favorable local tolerability. The most common adverse events with oral and vaginal tolterodine were headache (n = 11) and dry mouth (n = 8). Vaginal rings releasing tolterodine represent a promising new formulation for overactive bladder treatment with little fluctuation of drug plasma levels. This is expected to lead to a more predictable and continuous therapeutic effect and a reduced frequency of side effects compared to oral tolterodine.

Pharmacotherapy in overactive bladder

Overactive bladder syndrome (OAB) has a high prevalence within the population and has a negative effect on quality of life. Although the precise pathophysiology has yet to be fully elucidated, pharmacotherapeutic agents have been developed targeting two main pathways, antimuscarinic drugs and β3-adrenoreceptor agonists. Conservative management strategies, for example, bladder training, should be used as first-line treatment, with pharmacotherapy used as an adjunct if this is insufficiently effective. Antimuscarinics have a moderate effect on treating the symptoms of OAB, are associated with side effects, particularly dry mouth, and have low adherence rates in the long term. No single agent has consistently shown superiority over another. Antimuscarinics can affect cognition and may contribute to the anticholinergic burden in elderly patients. Mirabegron, a β3-agonist, appears to be as effective as antimuscarinics in improving symptoms of OAB with fewer side effects and improved adherence, and is currently recommended if treatment with antimuscarinics has failed. A combination of an antimuscarinic and β3-agonist may be worth considering if symptoms remain refractory or to reduce the side-effect profile associated with higher doses of antimuscarinics.

Level of evidence: Not applicable.

Tolterodine treatment of women with overactive bladder syndrome: Comparison of night-time and daytime dosing for nocturia

AIM

We aimed to clarify the impact of night-time dosing with tolterodine extended release (ER) on nocturia.

METHODS

The bladder diaries, urodynamic studies, and medical records of female patients with overactive bladder syndrome who were diagnosed between January 2005 and December 2015, and treated with tolterodine ER 4 mg once per day (night-time or daytime dosing) for 12 weeks in the urogynecology outpatient clinics of two tertiary referral centers were reviewed retrospectively.

RESULTS

A total of 72 female patients were reviewed. Thirty-six patients were in the daytime dosing group, and the other 36 patients were in the night-time dosing group. In the daytime dosing group, a decrease in the volume of fluid intake was found at 06.00-12.00, 12.00-18.00, and 18.00-24.00 hours, and a decrease in total voided volume was found at 12.00-18.00, 18.00-24.00, and 24.00-06.00 hours with a between-group difference at 18.00-24.00 hours (coefficient = 542 mL, P = 0.01). In the night-time dosing group, an increase in voided volume per micturition was found at 06.00-12.00 and 24.00-06.00 hours with a between-group difference at 24.00-6.00 hours (coefficient = 92 mL, P = 0.003) compared with the daytime dosing group. Nonetheless, pre-treatment proportions of nocturnal polyuria did not differ from post-treatment proportions (night-time: 20% vs 20%, P = 1.00; daytime: 48% vs 42%, P = 0.48). Decreases in the number of voiding and urgency episodes at nearly all time periods and increases in the volumes at strong desire to void were also found in both groups.

CONCLUSION

Night-time dosing of tolterodine ER may benefit female patients suffering from nocturia due to a greater voided volume per micturition at midnight.

Fesoterodine clinical efficacy and safety for the treatment of overactive bladder in relation to patient profiles: a systematic review

OBJECTIVE

To summarize published evidence on the pharmacology, efficacy, and safety of fesoterodine for the treatment of overactive bladder (OAB) symptoms in relation to patient clinical and demographic profiles.

METHODS

A systematic review of published articles on fesoterodine was conducted via a PubMed search. Articles were identified using the search term fesoterodine, with limits of human species and abstract available. Review and meta-analysis articles, validation studies, articles focused on treatment compliance/adherence, meeting abstracts, and articles not focused on oral fesoterodine administration in human subjects were excluded. Data from retained articles were summarized descriptively.

RESULTS

Of 137 articles identified, 61 (15 articles on the pharmacology and 46 articles on the efficacy and/or safety of fesoterodine) met inclusion criteria. Superiority trials demonstrated the additional efficacy of fesoterodine 8 mg versus fesoterodine 4 mg and tolterodine extended release 4 mg in treating OAB. Prospective trials in specific patient populations indicated beneficial effects of fesoterodine in elderly patients, vulnerable elderly patients, patients dissatisfied with or with a suboptimal response to previous antimuscarinic therapy, patients with urge urinary incontinence (UUI) or nocturnal urgency, and men with persistent LUTS during alpha-blocker treatment. With two effective doses, the fesoterodine dose can be adjusted to achieve optimal efficacy and tolerability in individual patients. The most common adverse events during fesoterodine treatment are dry mouth and constipation.

CONCLUSIONS

Extensive evidence demonstrates the efficacy and safety of fesoterodine in relieving OAB symptoms, including urgency, urinary frequency, UUI, and nocturnal urgency, in patients with various clinical and demographic profiles. Trial results provide valuable information on fesoterodine treatment in specific patient populations, including both elderly and vulnerable elderly patients. Potential limitations of this review are that only English language articles in PubMed were searched and included.

Tolterodine extended release in the treatment of male OAB/storage LUTS: a systematic review

Background

Overactive bladder (OAB)/ storage lower urinary tract symptoms (LUTS) have a high prevalence affecting up to 90% of men over 80 years. The role of sufficient therapies appears crucial. In the present review, we analyzed the mechanism of action of tolterodine extended-release (ER) with the aim to clarify its efficacy and safety profile, as compared to other active treatments of OAB/storage LUTS.

Methods

A wide Medline search was performed including the combination of following words: “LUTS”, “BPH”, “OAB”, “antimuscarinic”, “tolterodine”, “tolterodine ER”. IPSS, IPSS storage sub-score and IPSS QoL (International Prostate Symptom Score) were the validated efficacy outcomes. In addition, the numbers of urgency episodes/24 h, urgency incontinence episodes/24 h, incontinence episodes/24 h and pad use were considered. We also evaluated the most common adverse events (AEs) reported for tolterodine ER.

Results

Of 128 retrieved articles, 109 were excluded. The efficacy and tolerability of tolterodine ER Vs. tolterodine IR have been evaluated in a multicenter, double-blind, randomized placebo controlled study in 1529 patients with OAB. A 71% mean reduction in urgency incontinence episodes was found in the tolterodine ER group compared to a 60% reduction in the tolterodine IR (p < 0.05). Few studies evaluated the clinical efficacy of α-blocker/tolterodine combination therapy. In patients with large prostates (prostate volume >29 cc) only the combination therapy significantly reduced 24-h voiding frequency (2.8 vs. 1.7 with tamsulosin, 1.4 with tolterodine, or 1.6 with placebo). A recent meta-analysis evaluating tolterodine in comparison with other antimuscarinic drugs demonstrated that tolterodine ER was significantly more effective than placebo in reducing micturition/24 h, urinary leakage episodes/24 h, urgency episodes/24 h, and urgency incontinence episodes/24 h. With regard to adverse events, tolterodine ER was associated with a good adverse event profile resulting in the third most favorable antimuscarinic. Antimuscarinic drugs are the mainstay of pharmacological therapy for OAB / storage LUTS; several studies have demonstrated that tolterodine ER is an effective and well tolerated formulation of this class of treatment.

Conclusion

Tolterodine ER resulted effective in reducing frequency urgency and nocturia and urinary leakage in male patients with OAB/storage LUTS. Dry mouth and constipation are the most frequently reported adverse events.

Pharmacokinetics and toxicity of antimuscarinic drugs for overactive bladder treatment in females

INTRODUCTION

Antimuscarinics (AMs) are the mainstay of pharmacological treatment of overactive bladder (OAB), a symptom complex defined by the presence of urinary urgency, usually associated with frequency and nocturia, with or without urgency urinary incontinence. The AMs used to treat OAB differ in their pharmacological profiles, which may affect their potential for causing adverse effects (AEs).

AREAS COVERED

The present article aims to review the literature about pharmacokinetics (PK) of the different AMs used in the treatment of OAB. Furthermore, the AEs related to the use of these drugs and their incidence are presented. This systematic review is based on material searched and obtained via Medline, Pubmed and EMBASE up to March 2012 using the search terms "adverse events, pharmacokinetics, tolerability" in combination with "darifenacin, fesoterodine, imidafenacin, oxybutynin, propiverine, solifenacin, tolterodine, and trospium."

EXPERT OPINION

Antimuscarinics are the first-line pharmacological treatment for OAB. Despite the development of new molecules that improve their efficacy/safety profile, there are some drugs that are pharmacokinetically more appropriate to be prescribed in specific populations such as patients with neurological disease or the elderly. Moreover, research should be encouraged in evaluating antimuscarinics in conjunction with other drugs such as estrogens or beta-agonists. The identification of prognostic criteria for pharmacological therapy would be helpful.

Comparison of pharmacokinetic variability of fesoterodine vs. tolterodine extended release in cytochrome P450 2D6 extensive and poor metabolizers

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Tolterodine and 5-hydroxymethyl tolterodine (5-HMT) are equipotent active moieties of tolterodine; 5-HMT is the singular active moiety of fesoterodine. The formation of 5-HMT from tolterodine occurs via CYP2D6, and some subjects are poor metabolizers CYP2D6. On the other hand, the formation of 5-HMT from fesoterodine occurs via ubiquitous esterases. Cross-study comparisons of data from phase 1 studies suggest that active moiety exposures are considerably more variable following tolterodine extended release vs. fesoterodine.

WHAT THIS STUDY ADDS

This head-to-head study confirmed the findings of reduced pharmacokinetic variability of fesoterodine and further delineates that tolterodine, and not 5-HMT, was the principal source of variability after administration of tolterodine extended release. The data suggest that fesoterodine delivers 5-HMT consistently, regardless of CYP2D6 status, with up to 40% higher bioavailability compared with tolterodine.

AIMS

Tolterodine and 5-hydroxymethyl tolterodine (5-HMT) are equipotent active moieties of tolterodine; 5-HMT is the singular active moiety of fesoterodine. Formation of 5-HMT from fesoterodine and tolterodine occurs via esterases and CYP2D6 respectively. This randomized, crossover, open-label, multiple-dose study in CYP2D6 extensive metabolizers (EMs) and poor metabolizers (PMs) compared the pharmacokinetics of fesoterodine vs. tolterodine extended release (ER).

METHODS

Subjects received fesoterodine and tolterodine ER with a ≥3-day washout period. Treatment comprised 4-mg once daily doses for 5 days escalated to 8-mg once daily for 5 days. Pharmacokinetics of active moieties were compared by drug, dose and genotype.

RESULTS

Active moiety exposures following fesoterodine and tolterodine ER increased proportional to dose in EMs and PMs. In EMs only, coefficients of variation for AUC and C(max) following fesoterodine (up to 46% and 48% respectively) were lower than those following tolterodine ER (up to 87% and 87% respectively). Following fesoterodine and tolterodine ER administration, active moiety exposures ranged up to sevenfold and 40-fold respectively. Mean urinary excretion of 5-HMT following fesoterodine 4 and 8 mg, respectively, was 0.44 and 0.89 mg in EMs and 0.60 and 1.32 mg in PMs. Following tolterodine ER 4 and 8 mg, it was 0.38 and 0.71 mg respectively (EMs only). Renal clearance was similar regardless of administered drug, dose or genotype.

CONCLUSIONS

Tolterodine, not 5-HMT, was the principal source of variability after tolterodine ER administration. Fesoterodine delivers 5-HMT with less variability than tolterodine, regardless of CYP2D6 status, with up to 40% higher bioavailability. The pharmacokinetics of fesoterodine were considerably less variable than TER.

Evaluation of an experimental urodynamic platform to identify treatment effects: a randomized, placebo-controlled, crossover study in patients with overactive bladder

AIMS

To evaluate a urodynamic platform designed to identify treatment effects in small numbers of patients after a short duration of treatment using a medication with known efficacy in overactive bladder (OAB).

METHODS

Twenty women with OAB were randomized in a crossover study with 7-day treatment periods with either tolterodine 4 mg long-acting (LA) or placebo and 7-day washout. Patients underwent urodynamic study (UDS) at baseline, 4-hr post-dose on Day 1 (PD1) and 4 hr post-dose on Day 7 (PD7) in each treatment period. The primary endpoint was the change from baseline in volume at maximum cystometric capacity (MCC) at PD7. As a result of dosing errors, some patients allocated to tolterodine in Period 1 mistakenly received placebo on Day 7. The data from the time points at which patients were dosed incorrectly were excluded from the per protocol (PP) analysis.

RESULTS

The PP and intent to treat (ITT) mean increase in volume at MCC on PD7 for tolterodine compared with placebo was 28.9% (P = 0.038, one-sided) and 23.2% (P = 0.008, one-sided), respectively. The PD7 mean increase in volume at first desire to void was 36.5% (P = 0.054, PP) and 40.3% (P = 0.008, ITT). No volume endpoint at PD1 was statistically significant. Of all the endpoints, MCC was the least variable.

CONCLUSIONS

This crossover design was able to detect a clinically meaningful and statistically significant treatment effect consistent with the previous reports of tolterodine. Despite multiple urodynamics per patient, the study was able to recruit quickly. This model is valuable for evaluating therapeutic effects for existing and novel treatments for OAB.

Specific pharmacokinetic aspects of the urinary tract

This chapter reviews the evidence for "specific" pharmacokinetics playing a role in currently marketed drugs intended to treat lower urinary tract (LUT) symptoms. Principles of drug targeting include intrinsic properties of drugs or organs as well as drug formulations to modify drug release or to create confinement of drug presence. Prodrugs and specific formulations to deliver high drug concentrations at the site(s) of action as well as other ways to manipulate drug distribution to achieve enrichment in target tissues are considered. In overactive bladder (OAB), specific formulations for oxybutynin have been introduced to reduce the level of side effects of the active drug. Extended release tablet formulations and a topical gel formulation have been introduced, with efficacy similar to immediate release (IR) tablets, but with a reduction in anticholinergic adverse effects. However, these modifications have not led to outstanding performance parameters compared to other anticholinergic drugs marketed as IR formulations. Urinary excretion is discussed as potential mechanism for targeting LUT symptoms, but no strong indications appear to exist that this mechanism would contribute for currently available drugs. Intravesical administration of drugs is not a preferred option and only considered for drugs like botulinum toxin, where the inconvenient application compensates for a reasonable degree of long-term efficacy in severe refractory OAB. Alpha acid glycoprotein binding is discussed as a potential factor to influence drug tissue distribution, and it is concluded that there is reasonable evidence that for tamsulosin this mechanism is responsible for the difference in free fraction of the drug observed in plasma and prostate, which could contribute to its relative absence of blood pressure effects in patients with LUT symptoms related to benign prostate hyperplasia (LUTS-BPH). The principle of irreversible inhibition of type II 5α-reductase as a tool to develop drugs to reduce prostatic levels of dihydrotestosterone is employed by both dutasteride and finasteride for treatment of LUTS-BPH. Of the mechanisms discussed, the principles employed for the 5α-reductase blockers and tamsulosin in this respect can be considered relatively specific for its urological indication.

Update on the management of overactive bladder: patient considerations and adherence

Overactive bladder (OAB) is a common condition that causes a profound impact on an individual’s overall health and quality of life. Muscarinic receptor antagonists are the mainstay of oral pharmacotherapy for OAB. Although all of the medications in this class are significantly more effective than placebo, they are also associated with more adverse events that may limit their overall use. Although newer preparations of these medications have sought to improve tolerability and efficacy through alternative routes of delivery and once-daily dosing, improved adherence to treatment and treatment persistence continue to be an ongoing challenge. An improved understanding of the factors involved in persistence of medical OAB therapy is imperative in efforts to optimize therapeutic benefits in this chronic and potentially morbid condition.

Clinical pharmacokinetics and pharmacodynamics of solifenacin

The succinate salt of solifenacin, a tertiary amine with anticholinergic properties, is used for symptomatic treatment of overactive bladder. Solifenacin peak plasma concentrations of 24.0 and 40.6 ng/mL are reached 3-8 hours after long-term oral administration of a 5 or 10 mg solifenacin dose, respectively. Studies in healthy adults have shown that the drug has high absolute bioavailability of about 90%, which does not decrease with concomitant food intake. Solifenacin has an apparent volume of distribution of 600 L, is 93-96% plasma protein bound, and probably crosses the blood-brain barrier. Solifenacin is eliminated mainly through hepatic metabolism via cytochrome P450 (CYP) 3A4, with about only 7% (3-13%) of the dose being excreted unchanged in the urine. Solifenacin metabolites are unlikely to contribute to clinical solifenacin effects. In healthy adults, total clearance of solifenacin amounts to 7-14 L/h. The terminal elimination half-life ranges from 33 to 85 hours, permitting once-daily administration. Urinary excretion plays a minor role in the elimination of solifenacin, resulting in renal clearance of 0.67-1.51 L/h. Solifenacin does not influence the activity of CYP1A1/2, 2C9, 2D6 and 3A4, and shows a weak inhibitory potential for CYP2C19 and P-glycoprotein in vitro; however, clinical drug-drug interactions with CYP2C19 and P-glycoprotein substrates are very unlikely. Exposure to solifenacin is increased about 1.2-fold in elderly subjects and about 2-fold in subjects with moderate hepatic and severe renal impairment, as well as by coadministration of the potent CYP3A4 inhibitor ketoconazole 200 mg/day. The full therapeutic effects of solifenacin occur after 2-4 weeks of treatment and are maintained upon long-term therapy. Although solifenacin pharmacokinetics display linearity at doses of 5-40 mg, no obvious dose dependency was observed in efficacy and tolerability studies. The efficacy of solifenacin (5 or 10 mg/day) is at least equal to that of extended-release (ER) tolterodine (4 mg/day) in reducing the mean number of micturitions per 24 hours and urgency episodes, and in increasing the volume voided per micturition. Solifenacin (5 mg/day) appears to be superior to ER tolterodine (4 mg/day) in reducing incontinence episodes (mean -1.30 vs -0.90, p = 0.018) and is superior to propiverine (20 mg/day) at the dose of 10 mg/day in reducing urgency (-2.30 vs -2.78, p = 0.012) and nocturia episodes. Based on withdrawal rates due to adverse effects during the 52-week treatment period, solifenacin appears to have better tolerability than immediate-release (IR) oxybutynin 10-15 mg/day and IR tolterodine 4 mg/day. With regard to the pharmacokinetics of solifenacin, and for safety reasons, doses exceeding 5 mg/day are not recommended for patients with moderate hepatic impairment (Child-Pugh score 7-9), patients with severe renal impairment (creatinine clearance <30 mL/min) and subjects undergoing concomitant therapy with CYP3A4 inhibitors.

A Case of Tolterodine Poisoning

We present a case of acute tolterodine overdose with anticholinergic toxidrome including drowsiness, confusion and pyrexia. Tolterodine was commonly used in recent years for the treatment of overactive bladder syndrome. Experience with acute tolterodine poisoning was limited. The pharmacology, clinical use and side effects of tolterodine were reviewed. The clinical manifestations, toxicology and management of tolterodine poisoning are discussed.

The pharmacokinetic profile of fesoterodine 8 mg with daytime or nighttime dosing

PURPOSE

Diurnal variation can affect drug pharmacokinetics. Fesoterodine is a new antimuscarinic drug for the treatment of overactive bladder (OAB). We estimated the relative bioavailability of 5-hydroxymethyl tolterodine (5-HMT), the active metabolite of fesoterodine, following nighttime and daytime administration.

METHODS

In this randomized, open-label, two-period, two-treatment crossover, single-dose study, healthy subjects received daytime and nighttime oral dosing of fesoterodine 8-mg sustained-release tablets, separated by a minimum 60-h washout period. Blood samples for 5-HMT PK determination were collected before dosing and at specified intervals up to 48 h postdose. Safety was assessed by adverse event (AE) reports.

RESULTS

Fourteen subjects completed the study. Plasma concentration versus time profiles (AUC) of 5-HMT were similar for daytime and nighttime dosing. Mean AUC(infinity) 5-HMT values were 47.9 and 51.4 ng h/mL for nighttime and daytime dosing, respectively; the mean time to reach maximum concentration (C(max)) values were 3.9 and 5.0 ng/mL, respectively. Nighttime versus daytime AUC(infinity) and C(max) ratios of 5-HMT were 93 and 79%, respectively; 90% confidence intervals (CIs) indicated equivalence for AUC(infinity) but not for C(max). The median time to reach maximum concentration (T(max)) was 5.0 h for both dosing regimens, and the mean terminal elimination half-life (T((1/2))) was 5.9 and 5.7 h for nighttime and daytime dosing, respectively. Seven treatment-related AEs, most commonly headache, occurred in five subjects.

CONCLUSIONS

The AUC values for daytime and nighttime administration of fesoterodine were equivalent. The 21% reduction in the C(max) for nighttime dosing is unlikely to be clinically relevant. No safety issues were apparent. These results support both daytime and nighttime administration of fesoterodine for OAB treatment.

Tolterodine extended-release for overactive bladder

Overactive bladder (OAB) is a common problem. Affected individuals suffer decreased quality of life and productivity. The mainstay of pharmacological treatment of OAB is antimuscarinic agents. Tolterodine was the first antimuscarinic drug designed specifically for treating OAB. Compared with the immediate-release (IR) drug, once-daily tolterodine extended-release (ER) releases the drug in a steady but constant manner lowering peak and trough drug levels. This translates to more constant serum concentrations and theoretically better patient tolerability. The dry mouth rate for the ER formulation has been reported to be lower than for the IR formulation. Recent literature strongly supports the efficacy and safety of tolterodine ER in carefully selected older men with OAB symptoms. Tolterodine ER is well tolerated and withdrawal rates are similar to those in placebo. Fesoterodine is a new antimuscarinic that shares the same active metabolite as tolterodine and may provide less pharmacokinetic variability. We support tolterodine ER for treating for OAB. It has proven efficacy and tolerability.

The effects of reformulation: improved therapeutic index

Antimuscarinic agents are the treatment of choice for overactive bladder syndrome. Due to the development of novel delivery systems, extended-release formulations of oxybutynin, tolterodine, and trospium chloride are now available. In addition to the convenience of once-daily dosing, the new formulations of these commonly prescribed agents have improved their therapeutic index, striking a better balance between efficacy and tolerability.

Disposition and antimuscarinic effects of the urinary bladder spasmolytics propiverine: influence of dosage forms and circadian-time rhythms

Propiverine extended release is expected to be better tolerated compared to immediate release tablets because of slower drug release and reduced formation of active metabolites in the colon. CYP3A4 and ABCC2, the major variables in pharmacokinetics of propiverine, are less expressed in the colon. Therefore, disposition and pharmacodynamics of propiverine were measured in a double-blind, double-dummy, crossover study with administration of 15 mg immediate release 3 times daily for 7 days compared to 45 mg extended release once daily for 7 days in 24 healthy subjects. Twelve subjects also received 15 mg propiverine intravenously. Serum and urine propiverine levels were measured repeatedly following oral administration on day 7 for up to 72 hours and correlated to duodenal expression of CYP3A4, ABCB1, and ABCC2. Propiverine immediate release 3 times daily was not different to extended release once daily in areas under the serum concentration-time curve (0-24 hours) and peak-trough fluctuation. The areas under the serum concentration-time curve of propiverine immediate release was circadian-time-dependent, with the lowest values during the night. Disposition of intravenous propiverine and propiverine immediate release administered in the night was influenced by intestinal expression of ABCC2. We concluded that oral absorption of propiverine is site-dependent and influenced by dosage form and circadian-time-dependent elimination processes.

Once daily trospium chloride is effective and well tolerated for the treatment of overactive bladder: results from a multicenter phase III trial

PURPOSE

An extended release formulation of trospium chloride was recently developed for the once daily treatment of overactive bladder. We investigated the safety, efficacy and tolerability of 60 mg trospium chloride once daily.

MATERIALS AND METHODS

Subjects with overactive bladder were randomized 1:1 to receive 60 mg trospium chloride once daily or placebo in this 12-week multicenter, parallel, double-blind, placebo controlled trial. Primary end points were calculated changes in diary recorded daily urinary frequency and daily urgency urinary incontinence episodes. Secondary end points were urgency severity, volume voided per void and the number of urgency voids per day. Safety was assessed by clinical examination, adverse event monitoring, clinical laboratory values and resting electrocardiograms.

RESULTS

Overall 601 subjects were prescribed trospium once daily (298) or placebo (303). Trospium once daily treatment resulted in significant improvements over placebo in all primary and key secondary efficacy outcomes at weeks 1 through 12. The most common adverse events were dry mouth (trospium 8.7% vs placebo 3%) and constipation (trospium 9.4% vs placebo 1.3%). Central nervous system adverse events were rare (headache with trospium 1.0% vs placebo 2.6%). No clinically meaningful changes in laboratory, physical examination or electrocardiogram parameters were noted.

CONCLUSIONS

Trospium once daily provided significant improvements in overactive bladder symptoms (frequency, urgency urinary incontinence and urgency). Efficacy was similar to that seen previously with trospium chloride twice daily, while class effect anticholinergic adverse events occurred at comparatively low levels. Dry mouth was elicited at the lowest reported rate in the oral antimuscarinic drug class.

The clinical efficacy of tolterodine extended-release is maintained for 24 h in patients with overactive bladder

OBJECTIVE

To assess the 24-h efficacy of tolterodine extended-release (ER) in patients with overactive bladder (OAB) and urgency urinary incontinence (UUI).

PATIENTS AND METHODS

We conducted a post hoc analysis of a 12-week, placebo-controlled trial of tolterodine-ER in patients with frequency (> or =8 voids/24 h) and UUI (> or=5 episodes/week) for > or = 6 months. Seven-day bladder diaries were used to record diary endpoints; 24-h diary data were stratified by 6-h periods beginning at midnight.

RESULTS

Compared with placebo (508 patients), tolterodine-ER (507 patients) significantly and consistently increased volume voided per void and reduced UUI episodes and micturition frequency during each interval.

CONCLUSIONS

These results indicate that tolterodine-ER maintained clinical efficacy over 24 h and should be effective for OAB symptoms without regard to whether symptoms occur during the day or at night.

Thorough QT Study with Recommended and Supratherapeutic Doses of Tolterodine

The objective of our study was to determine the QTc effects of tolterodine. A crossover-design thorough QT study of recommended (2 mg twice daily) and supratherapeutic (4 mg twice daily) doses of tolterodine, moxifloxacin (400 mg once daily), and placebo was performed. Electrocardiograms (ECGs) and pharmacokinetic samples were obtained on days 1-4; time-matched baseline ECGs were taken on day 0. Mean placebo-subtracted change from baseline Fridericia-corrected QT (QTcF) during peak drug exposure on day 4 was the primary end point. Mean QTcF prolongation of moxifloxacin was 8.9 ms (machine-read) and 19.3 ms (manual-read). At recommended and supratherapeutic tolterodine doses, mean QTcF prolongation was 1.2 and 5.6 ms (machine-read), respectively, and 5.0 and 11.8 ms (manual-read), respectively. The QTc effect of tolterodine was lower than moxifloxacin. No subject receiving tolterodine exceeded the clinically relevant thresholds of 500 ms absolute QTc or 60 ms change from baseline. In conclusion, tolterodine does not have a clinically significant effect on QT interval.

Muscarinic receptors in the bladder: from basic research to therapeutics

Muscarinic receptor antagonists (antimuscarinics) serve as the cornerstone in the pharmacological management of overactive bladder (OAB) by relieving the symptoms of urgency, frequency and incontinence. These drugs operate primarily by antagonizing post-junctional excitatory muscarinic receptors (M(2)/M(3)) in the detrusor. The combination of pharmacological and gene knockout studies has greatly advanced our understanding of the functional role of muscarinic receptors in the bladder. M(3) receptors produce direct smooth muscle contraction by a mechanism that relies on entry of extracellular calcium through L-type channels and activation of a rho kinase. M(2) receptors, which predominate in number, appear to facilitate M(3)-mediated contractions. M(2) receptors can also produce bladder contractions indirectly by reversing cAMP-dependent beta-adrenoceptor-mediated relaxation, although the physiological role of beta-adrenoceptors in detrusor relaxation is controversial. Emerging evidence suggests that muscarinic receptors in the urothelium/suburothelium can modulate the release of certain factors, which in turn may affect bladder function at the efferent or afferent axis. Currently, oxybutynin, tolterodine, darifenacin, solifenacin and trospium are the five major antimuscarinics approved for the treatment of OAB. Comparative clinical studies have shown that oxybutynin and solifenacin may be marginally more effective than tolterodine, although the latter seems to be better tolerated. Pharmacokinetic-pharmacodynamic analyses using plasma concentrations of 'total drug' indicate that, at therapeutic doses, the clinical efficacy of darifenacin and solifenacin may be driven primarily by selective M(3) receptor occupation, whereas the pharmacodynamic effects of pan-selective molecules (such as tolterodine, trospium) may potentially involve multiple receptors, including M(2) and M(3). Furthermore, high M(3) receptor occupation is the likely explanation for the greater propensity of darifenacin and oxybutynin to cause dry mouth and/or constipation. Although the recently introduced drugs represent a significant improvement over older drugs, especially with respect to the convenience of dosing schedule, their overall efficacy and tolerability profile is still less than optimal and patient persistence with therapy is low. Recent advances in basic research have not yet offered a clear discovery path for improving the therapeutic index of antimuscarinic molecules. There is still an unmet need for an antimuscarinic medicine with superior clinical effectiveness that can translate into better persistence on therapy.

Pharmacogenetics, drug-metabolizing enzymes, and clinical practice

The application of pharmacogenetics holds great promise for individualized therapy. However, it has little clinical reality at present, despite many claims. The main problem is that the evidence base supporting genetic testing before therapy is weak. The pharmacology of the drugs subject to inherited variability in metabolism is often complex. Few have simple or single pathways of elimination. Some have active metabolites or enantiomers with different activities and pathways of elimination. Drug dosing is likely to be influenced only if the aggregate molar activity of all active moieties at the site of action is predictably affected by genotype or phenotype. Variation in drug concentration must be significant enough to provide "signal" over and above normal variation, and there must be a genuine concentration-effect relationship. The therapeutic index of the drug will also influence test utility. After considering all of these factors, the benefits of prospective testing need to be weighed against the costs and against other endpoints of effect. It is not surprising that few drugs satisfy these requirements. Drugs (and enzymes) for which there is a reasonable evidence base supporting genotyping or phenotyping include suxamethonium/mivacurium (butyrylcholinesterase), and azathioprine/6-mercaptopurine (thiopurine methyltransferase). Drugs for which there is a potential case for prospective testing include warfarin (CYP2C9), perhexiline (CYP2D6), and perhaps the proton pump inhibitors (CYP2C19). No other drugs have an evidence base that is sufficient to justify prospective testing at present, although some warrant further evaluation. In this review we summarize the current evidence base for pharmacogenetics in relation to drug-metabolizing enzymes.

Tolterodine for Treatment of Overactive Bladder

Tolterodine was developed as an antimuscarinic agent specifically for the treatment of overactive bladder. Initial in vivo studies demonstrated a functional selectivity for the muscarinic receptors in the urinary bladder over the salivary glands, and subsequent clinical trials showed an overall superior tolerability profile compared with other drugs in the same class (ie, oxybutynin). With immediate- and extended-release formulations and sustained clinical efficacy during long-term treatment, tolterodine gas become an important treatment option for the symptoms of overactive bladder.

Treatment of the overactive bladder syndrome with muscarinic receptor antagonists - a matter of metabolites?

Antagonists of muscarinic acetylcholine receptors, such as darifenacin, oxybutynin, propiverine, solifenacin, tolterodine, and trospium, are the mainstay of the treatment of the overactive bladder syndrome. Fesoterodine is a newer drug awaiting regulatory approval. We briefly review the pharmacological activity of their metabolites and discuss how active metabolites may contribute to their efficacy and tolerability in vivo. Except for trospium, and perhaps solifenacin, all of the above drugs form active metabolites, and their presence and activity need to be taken into consideration when elucidating relationships between pharmacokinetics and pharmacodynamics of these drugs. Moreover, the ratios between parent compounds and metabolites may differ depending on genotype of the metabolizing enzymes, concomitant medication, and/or drug formulation. Differential generation of active metabolites of darifenacin or tolterodine are unlikely to influence the overall clinical profile of these drugs in a major way because the active metabolites exhibit a similar pharmacological profile as the parent compound. In contrast, metabolites of oxybutynin and propiverine may behave quantitatively or even qualitatively differently from their parent compounds and this may have an impact on the overall clinical profile of these drugs. We conclude that more comprehensive studies of drug metabolites are required for an improved understanding of their clinical effects.

Effect of the proton pump inhibitor omeprazole on the pharmacokinetics of extended-release formulations of oxybutynin and tolterodine

This study assessed the effect of the proton pump inhibitor omeprazole on the bioavailability of the extended-release formulations of oxybutynin and tolterodine. Forty-four healthy volunteers received each of 4 treatments in a 4-period crossover design. The treatments consisted of osmotically controlled extended-release oxybutynin chloride tablets at 10 mg/d or extended-release tolterodine tartrate capsules at 4 mg/d, with and without preceding treatment with 20 mg omeprazole daily for 4 days. Blood samples collected predose and at scheduled time points for 36 hours postdose were analyzed for oxybutynin and its active metabolite, N-desethyloxybutynin, or tolterodine and its active 5-hydroxymethyl metabolite, as appropriate. The AUCinfinity ratios for oxybutynin and its metabolite with and without prior omeprazole fell within the 80% to 125% range (accepted as the criterion for bioequivalence), as did those for tolterodine and its active moiety. The peak concentration ratios for oxybutynin and metabolite also conformed to this range; those for tolterodine did not. Increasing gastric pH with omeprazole does not substantially alter the pharmacokinetic properties of extended-release oxybutynin but may alter those of extended-release tolterodine.

Nighttime dosing with tolterodine reduces overactive bladder-related nocturnal micturitions in patients with overactive bladder and nocturia

OBJECTIVES

To evaluate the efficacy and tolerability of nighttime tolterodine dosing on urgency-related micturitions in patients with overactive bladder (OAB) and nocturia.

METHODS

This was a 12-week randomized controlled study of 850 patients given 4 mg tolterodine extended release (TER) or placebo once daily 4 hours or less before bed. Patients with eight or more micturitions/24 hours and a mean of 2.5 episodes/night or more were included. Changes in the number of nighttime and 24-hour micturitions were analyzed by urgency rating per micturition. The urgency per micturition was recorded in 7-day diaries using a 5-point rating scale (score 1 to 5). Each micturition was classified according to the following urgency rating categories: total (1 to 5), non-OAB (1 to 2), or OAB (3 to 5). OAB-related micturitions were further classified as nonsevere (score 3) and severe (score 4 to 5).

RESULTS

TER reduced the total number of nocturnal micturitions, but, compared with placebo, this difference was not statistically significant. However, TER did significantly reduce OAB-related and severe OAB-related nocturnal micturitions compared with placebo. TER had no effect on non-OAB micturitions. TER significantly reduced the total, OAB, and severe OAB micturitions during 24-hour and daytime intervals compared with placebo. Significantly more TER-treated than placebo-treated patients reported a treatment benefit and willingness to continue treatment. Adverse events associated with nighttime dosing of TER versus placebo were few.

CONCLUSIONS

TER significantly reduced OAB-related micturitions during 24-hour, daytime, and nighttime intervals. TER did not affect normal (non-OAB) micturitions. Nighttime dosing with TER was associated with few adverse events and adverse event-related withdrawals. The 24-hour efficacy of TER was maintained with nighttime dosing.

Muscarinic receptors: their distribution and function in body systems, and the implications for treating overactive bladder

1. The effectiveness of antimuscarinic agents in the treatment of the overactive bladder (OAB) syndrome is thought to arise through blockade of bladder muscarinic receptors located on detrusor smooth muscle cells, as well as on nondetrusor structures. 2. Muscarinic M3 receptors are primarily responsible for detrusor contraction. Limited evidence exists to suggest that M2 receptors may have a role in mediating indirect contractions and/or inhibition of detrusor relaxation. In addition, there is evidence that muscarinic receptors located in the urothelium/suburothelium and on afferent nerves may contribute to the pathophysiology of OAB. Blockade of these receptors may also contribute to the clinical efficacy of antimuscarinic agents. 3. Although the role of muscarinic receptors in the bladder, other than M3 receptors, remains unclear, their role in other body systems is becoming increasingly well established, with emerging evidence supporting a wide range of diverse functions. Blockade of these functions by muscarinic receptor antagonists can lead to similarly diverse adverse effects associated with antimuscarinic treatment, with the range of effects observed varying according to the different receptor subtypes affected. 4. This review explores the evolving understanding of muscarinic receptor functions throughout the body, with particular focus on the bladder, gastrointestinal tract, eye, heart, brain and salivary glands, and the implications for drugs used to treat OAB. The key factors that might determine the ideal antimuscarinic drug for treatment of OAB are also discussed. Further research is needed to show whether the M3 selective receptor antagonists have any advantage over less selective drugs, in leading to fewer adverse events.

Muscarinic acetylcholine receptors as effector sites for present and future therapeutic applications: focus on non-neural cholinergic systems

This review summarises the expression and function of muscarinic acetylcholine receptors (mAChR) in the organism, and the therapeutic implications of recent patents on cholinergic agents. Aside from the well known therapeutic applications of parasympathomimetic and -lytic drugs for diseases of the heart, eye, circulation and airways, new possible fields for mAChR agonists and antagonists in clinical therapy have begun to emerge. In particular, the role of non-neural cholinergic mechanisms in tissue regeneration, development and even carcinogenesis has become increasingly studied by a number of research teams within the last decade. This review exemplifies and contrasts experimental findings of mAChR drug action, and discusses these with regard to patents from the past 4 years.

Tolterodine for the treatment of overactive bladder: a review

Overactive bladder (OAB) is a prevalent condition. Numerous clinical trials have demonstrated the efficacy and safety of immediate release tolterodine in the treatment of OAB in different patient populations. This review details the characteristics, clinical efficacy and safety of extended release (ER) tolterodine. This formulation yields a flatter serum concentration profile and provides clinically meaningful symptom improvement as early as week 1 of treatment. Tolterodine ER is effective in diverse patient populations with varying levels of symptom severity, and efficacy is maintained with long-term treatment. Tolterodine is an effective, safe, and convenient treatment option for long-term relief of OAB symptoms.

TOLTERODINE TREATMENT FOR CHILDREN WITH SYMPTOMS OF URINARY URGE INCONTINENCE SUGGESTIVE OF DETRUSOR OVERACTIVITY: RESULTS FROM 2 RANDOMIZED, PLACEBO CONTROLLED TRIALS

PURPOSE

We report the results of the first 2 large randomized controlled trials designed to evaluate the efficacy and safety of tolterodine extended release in children 5 to 10 years old with symptoms of urinary urge incontinence suggestive of detrusor overactivity.

MATERIALS AND METHODS

Two double-blind, placebo controlled trials were conducted sequentially. Children 5 to 10 years old with incontinence suggestive of detrusor overactivity (1 or more diurnal incontinence episodes per 24 hours) were randomized to tolterodine (2 mg daily) or placebo for 12 weeks. The primary end point was the change from baseline to week 12 in the number of incontinence episodes per week. Changes from baseline in the number of voids per 24 hours and volume of urine per void were also evaluated. Exploratory analyses were conducted to determine whether particular subsets of patients showed differential responses to treatment.

RESULTS

A total of 224 and 487 children (mean age 8 years) were randomized to placebo and tolterodine, respectively. Differences in the number of incontinence episodes per week, voids per 24 hours, and volume of urine per void between tolterodine and placebo did not reach statistical significance. This finding may be explained by a high placebo response and under dosage of tolterodine among children with greater body weight. Tolterodine was well tolerated.

CONCLUSIONS

Analysis of the primary efficacy outcome did not reveal a statistically significant effect of treatment. However, secondary analyses demonstrated that tolterodine was well tolerated among 5 to 10-year-old children with diurnal incontinence. Exploratory analyses also showed that children weighing 35 kg or less with detrusor overactivity characterized by incontinence and/or frequent voiding benefited most from tolterodine treatment, suggesting that a weight adjusted dosing regimen may be required for optimal response among older and heavier children.

Comparison of the efficacy of tolterodine and oxybutynin in different urodynamic severity grades of idiopathic detrusor overactivity

OBJECTIVE

To compare the efficacy of tolterodine and oxybutynin in the treatment of specific, according to their urodynamic grade of severity, populations with overactive detrusor.

METHODS

In this open, randomized, two-way crossover study 128 women with urodynamically confirmed, idiopathic detrusor overactivity were recruited. Patients were categorized in 4 grades of severity groups, according to the characteristics of the first overactive detrusor contraction during filling cystometrogram: high volume-low pressure (grade-group I), high volume-high pressure (grade-group II), low volume-low pressure (grade-group III) and low volume-high pressure (grade-group IV). The primary outcome measure was average volume of voided urine per micturition.

RESULTS

107 patients successfully completed the study protocol and were included in the analyses: 40 in group IV, 36 in III, 25 in II and 6 in group I. In groups IV and III both oxybutynin and tolterodine significantly increased the average volume of voided urine per micturition but the differences between the drugs were not significant (p > 0.05). In group II neither of the drugs achieved significant changes in the outcome measure (p > 0.05).

CONCLUSIONS

Tolterodine and oxybutynin are clinically equipotent in treating detrusor overactivity in specific severity groups of patients, although urodynamic effects are somewhat different.

Solifenacin demonstrates high absolute bioavailability in healthy men

OBJECTIVE

Solifenacin succinate (YM905; Vesicare) is a promising new bladder selective muscarinic receptor antagonist under investigation for the treatment of overactive bladder. This study was designed to assess the absolute bioavailability of a single oral dose of solifenacin 10 mg, which is twice the suggested starting dose.

STUDY DESIGN

Single-centre, open-label, randomised, two-period, crossover, single-dose study.

METHODS

Solifenacin was administered orally as a 10 mg dose and intravenously as a 5 mg dose. Oral and intravenous (IV) doses were divided by a washout period of > or =14 days.

STUDY PARTICIPANTS

The study group consisted of 12 healthy young men, aged 20-45 years, nine of whom completed the study.

RESULTS

The pharmacokinetic analysis comprised nine subjects. A single oral dose of solifenacin 10 mg had a high absolute bioavailability of 88.0% (95% confidence interval 75.8, 102.1), low clearance (9.39 L/h [SD 2.68]), and an extensive mean volume of distribution at steady state (599L [SD 86]). Only 7% of solifenacin was excreted intact in the urine. Single oral and IV administration of solifenacin was well tolerated in this study. The most common adverse events related to drug treatment were headache and somnolence.

CONCLUSIONS

Pharmacokinetic analyses of single oral and IV doses of solifenacin demonstrated that the drug has a high absolute oral availability of 88%. This finding suggests that solifenacin may have a higher and less variable bioavailability than other antimuscarinic agents.

Central nervous system safety of anticholinergic drugs for the treatment of overactive bladder in the elderly

BACKGROUND

Overactive bladder (OAB) is characterized by urgency and increased frequency of micturition, with or without urinary urge incontinence. Anticholinergic agents are important in the treatment of OAB. However, concerns have emerged about their central nervous system (CNS) safety and the associated risk of cognitive impairment.

OBJECTIVE

This article describes the CNS adverse effects of anticholinergic drugs used for the treatment of OAB, with particular emphasis on their use in the elderly. Its objective is to help physicians make optimal choices when selecting anticholinergic treatment for OAB.

METHODS

: Relevant data from the literature were identified primarily through a MEDLINE search of articles published through December 2003. The search terms included overactive bladder, central nervous system, anticholinergic, and antimuscarinic. This was not intended to be a systematic review, and articles were chosen for inclusion based on their pertinence to the focus on treatment of OAB in the elderly.

RESULTS

Several anticholinergic drugs are available for the treatment of OAB, including oxybutymn, tolterodine, trospium chloride, and propiverine (not available in the United States). Among the agents reviewed, penetration of the blood-brain barrier (as predicted by lipophilicity, polarity, and molecular size and structure) is highest for oxybutymn, lower for tolterodine, and lowest for trospium chloride; limited data are available for propiverine. The total anticholinergic drug burden may also be important in determining the potential for CNS adverse effects. The spectrum of anticholinergic CNS adverse effects ranges from drowsiness to hallucinations, severe cognitive impairment, and even coma. The immediate-release (IR) and extended-release (ER) formulations of oxybutynin have been associated with cognitive impairment. In the only published clinical trial that was identified, no significant differences in CNS adverse effects were observed between the IR and ER formulations of tolterodine. There were few clinical data on the use of propiverine in patients with OAB. Trospium chloride has shown favorable CNS tolerability in postmarketing surveillance studies.

CONCLUSION

When considering treatment choices for patients with OAB, particularly the elderly, the potential CNS adverse effects of each anticholinergic agent must be weighed against the severity of OAB symptoms.

Improving the Tolerability of Anticholinergic Agents in the Treatment of Overactive Bladder

Pharmacological treatment for overactive bladder has centred around the interruption of the detrusor activity that is central to urge and incontinence symptoms. The majority of patients with this disorder are treated with antimuscarinic agents. These drugs have been demonstrated to improve urgency, frequency of micturition and urge incontinence, all of which are primary symptoms of overactive bladder; however, they are also commonly associated with anticholinergic adverse effects, most notably dry mouth. Attempts to increase tolerability have included the development of advanced formulations that regulate release of the active ingredient and the development of pharmacological agents that target the desired bladder receptors more specifically and accurately. Although all agents provide good efficacy, tolerability is greatly affected by the formulation used to deliver the active pharmacological agent, as well as the specificity of the targeted receptors. Clinical trials involving a transdermal formulation of oxybutynin have shown that this delivery method may be associated with a lower incidence of anticholinergic adverse events compared with both the immediate-release and the extended-release oral formulations of traditional agents, as well as the most recently approved agents - trospium chloride, solifenacin and darifenacin. Much is still being learned about the function and specificity of muscarinic receptors, which will support the development of agents with sustained efficacy and enhanced tolerability compared with the available formulations to date. These include the S-isomer of oxybutynin, as well as selective muscarinic M2 receptor antagonists.

Clinical pharmacokinetics of drugs used to treat urge incontinence

Urge incontinence (also known as overactive bladder) is a common form of urinary incontinence, occurring alone or as a component of mixed urinary incontinence, frequently together with stress incontinence. Because of the pathophysiology of urge incontinence, anticholinergic/antispasmodic agents form the cornerstone of therapy. Unfortunately, the pharmacological activity of these agents is not limited to the urinary tract, leading to systemic adverse effects that often promote nonadherence. Although the pharmacokinetics of flavoxate, propantheline, scopolamine, imipramine/desipramine, trospium chloride and propiverine are also reviewed here, only for oxybutynin and tolterodine are there adequate efficacy/tolerability data to support their use in urge incontinence. Oxybutynin is poorly absorbed orally (2-11% for the immediate-release tablet formulation). Controlled-release oral formulations significantly prolong the time to peak plasma concentration and reduce the degree of fluctuation around the average concentration. Significant absorption occurs after intravesical (bladder) and transdermal administration, although concentrations of the active N-desethyl metabolite are lower after transdermal compared with oral administration, possibly improving tolerability. Food has been found to significantly affect the absorption of one of the controlled-release formulations of oxybutynin, enhancing the rate of drug release. Oxybutynin is extensively metabolised, principally via N-demethylation mediated by the cytochrome P450 (CYP) 3A isozyme. The pharmacokinetics of tolterodine are dependent in large part on the pharmacogenomics of the CYP2D6 and 3A4 isozymes. In an unselected population, oral bioavailability of tolterodine ranges from 10% to 74% (mean 33%) whereas in CYP2D6 extensive metabolisers and poor metabolisers mean bioavailabilities are 26% and 91%, respectively. Tolterodine is metabolised via CYP2D6 to the active metabolite 5-hydroxymethyl-tolterodine and via CYP3A to N-dealkylated metabolites. Urinary excretion of parent compound plays a minor role in drug disposition. Drug effect is based upon the unbound concentration of the so-called 'active moiety' (sum of tolterodine + 5-hydroxymethyl-tolterodine). Terminal disposition half-lives of tolterodine and 5-hydroxymethyl-tolterodine (in CYP2D6 extensive metabolisers) are 2-3 and 3-4 hours, respectively. Coadministration of antacid essentially converts the extended-release formulation into an immediate-release formulation. Knowledge of the pharmacokinetics of these agents may improve the treatment of urge incontinence by allowing the identification of individuals at high risk for toxicity with 'usual' dosages. In addition, the use of alternative formulations (controlled-release oral, transdermal) may also facilitate adherence, not only by reducing the frequency of drug administration but also by enhancing tolerability by altering the proportions of parent compound and active metabolite in the blood.