Comparative evaluation of central muscarinic receptor binding activity by oxybutynin, tolterodine and darifenacin used to treat overactive bladder

PURPOSE: We characterized muscarinic receptor binding in the mouse cerebral cortex after oral administration of anticholinergic agents used to treat overactive bladder. MATERIALS AND METHODS: Muscarinic receptors in the mouse cerebral cortex and bladder after oral administration of anticholinergic agents were measured using [(3)H]N-methylscopolamine. RESULTS: In vitro binding affinities of tolterodine and its metabolite 5-hydroxymethyl metabolite in the mouse cerebral cortex and bladder were considerably greater than those of oxybutynin and darifenacin. Also, muscarinic receptor binding affinity of oxybutynin and its metabolite N-desethyl-oxybutynin in the cerebral cortex compared with that in the bladder was 2 to 3 times higher, whereas that of tolterodine and 5-hydroxymethyl metabolite was approximately 2 times lower. Oral administration of oxybutynin (76.1 micromol/kg), tolterodine (6.31 micromol/kg) and darifenacin (59.1 micromol/kg) showed binding activity that was approximately equal to that of bladder muscarinic receptors. Oral administration of oxybutynin (76.1 micromol/kg) showed significant binding of cerebral cortical muscarinic receptors in mice, as indicated by about a 2-fold increase in K(d) values for specific [(3)H]N-methylscopolamine binding 0.5 and 2 hours later. On the other hand, tolterodine and darifenacin given at oral doses that would exert a similar extent of bladder receptor binding activity as oxybutynin showed only a low level of binding activity of central muscarinic receptors in mice. CONCLUSIONS: Significant binding of brain muscarinic receptors in mice was observed by the oral administration of oxybutynin but not tolterodine and darifenacin.     

Muscarinic receptor antagonists for overactive bladder

Overactive bladder (OAB) is a syndrome characterized by urinary urgency, with or without urgency urinary incontinence, usually with frequency and nocturia. OAB symptoms are often associated with detrusor overactivity (DO). Like OAB symptoms, the prevalence of DO increases with age and can have a neurogenic and/or myogenic aetiology. Bladder outlet obstruction can be a contributing factor in DO, possibly through cholinergic denervation of the detrusor and supersensitivity of muscarinic receptors to acetylcholine, although the prevalence of OAB is similar in men and women across age groups. Acetylcholine is the primary contractile neurotransmitter in the human detrusor, and antimuscarinics exert their effects on OAB/DO by inhibiting the binding of acetylcholine at muscarinic receptors M(2) and M(3) on detrusor smooth muscle cells and other structures within the bladder wall. Worldwide, there are six antimuscarinic drugs currently marketed for the treatment of OAB: oxybutynin, tolterodine, propiverine, trospium, darifenacin, and solifenacin. Each has demonstrated efficacy for the treatment of OAB symptoms, but their pharmacokinetic and adverse event profiles differ somewhat due to structural differences (tertiary vs quaternary amines), muscarinic receptor subtype selectivities, and organ selectivities. Antimuscarinics are generally well tolerated, even in special populations (e.g. men with bladder outlet obstruction, elderly patients, children). The most frequently reported adverse events in clinical studies of antimuscarinics are dry mouth, constipation, headache, and blurred vision; few patients withdraw from clinical trials because of adverse events. Development of an antimuscarinic with functional selectivity for the bladder would reduce the occurrence of antimuscarinic adverse events. The therapeutic potential of several other agents, such as alpha(3)-adrenoceptor agonists, purinergic receptor antagonists, phosphodiesterase inhibitors, neurokinin-1 receptor antagonists, opioids, and Rho-kinase inhibitors, is also under investigation for the treatment of OAB.     

Pharmacological effects of KRP-197 on the human isolated urinary bladder

KRP-197, 4-(2-methylimidazol-l-yl)-2,2-diphenylbutyramide, is a newly synthesized antimuscarinic drug, developed for the treatment for overactive bladder. For evaluation of pharmacological characteristics of KRP-197, we investigated whether it influenced both prejunctional and postjunctional muscarinic receptors on the isolated human detrusor smooth muscles as compared with the effects of atropine, oxybutynin, and propiverine. Using the muscle bath technique, we investigated the effects of various antimuscarinic drugs on the contractions induced by carbachol, KCl, CaCl(2), and electrical field stimulation. Furthermore, using high-performance liquid chromatography with a microdialysis technique, we measured the acetylcholine release from the muscle strips during electrical field stimulation. The effects of various antimuscarinic drugs on acetylcholine releases were also evaluated. Pretreatment with various antimuscarinic drugs caused parallel shifts to the right in carbachol-induced concentration-response curves. The rank order of pA(2) values was KRP-197 > or = atropine > oxybutynin > propiverine. Atropine and KRP-197 did not cause significant inhibition of KCl- and CaCl(2)-induced contractions. All drugs caused concentration-dependent inhibitions in electrical field stimulation-induced contractions. Pretreatment with atropine and propiverine did not cause significant changes in electrical field stimulation-induced acetylcholine release. However, KRP-197, and oxybutynin caused significant decreases in acetylcholine release. The present study demonstrates that KRP-197 has an inhibitory effect on postjunctional muscarinic receptors as well as on prejunctional muscarinic receptors to modulate acetylcholine release in human detrusor smooth muscles. The findings suggest the usefulness of KRP-197 as a therapeutic drug for an overactive bladder with symptoms of frequency, urgency, and urge incontinence.     

Actions of the new antimuscarinic compound Lu 25-109 on isolated human and pig detrusor

The aim of this study was to evaluate the effects of a novel antimuscarinic agent, Lu 25-109, a partial M1 receptor agonist, and M2/M3 receptor antagonist in human and pig detrusor to establish its affinity for muscarinic receptors in human detrusor and parotid gland and to compare the results with those obtained with oxybutynin. Effects on the detrusor were determined as regards the ability to inhibit carbachol-induced contractions and contractions induced by electrical field stimulation (EFS). Radioligand binding studies were performed to assess the ability to displace quinuclidinyl benzilate (3H-QNB) from muscarinic receptors in the detrusor and parotid gland. Lu 25-109 produced a concentration-dependent rightward shift of the concentration-response curves for carbachol in both human and pig detrusor, the pK(b) values being 6.2+/-0.1 (n=6) and 5.8+/-0.3 (n=6). Corresponding values for oxybutynin were 7.9+/-0.1 (n=7) and 7.8+/-0.1 (n=6). Contractions induced by EFS in human detrusor were almost completely inhibited by 100 micromol/L Lu 25-109 (84+/-4%; n=4). In contrast, EFS-induced contractions in pig detrusor were less sensitive to Lu 25-109, resulting in a final inhibition of 32+/-6% (n=9) with the highest concentration used (100 micromol/L). This difference in effect between human and pig detrusor was not observed with oxybutynin. Radioligand binding experiments demonstrated a small difference in affinity for Lu 25-109 in the parotid gland compared with the bladder, the pKi values being 6.2+/-0.1 versus 6.5+/-0.1 (n=4). Corresponding values for oxybutynin were 8.5+/-0.1 versus 8.2+/-0.1 (n=4). The results show that Lu 25-109 competitively and effectively antagonizes carbachol-induced contractions and contractions induced by EFS in human detrusor muscle. Even if Lu 25-109 were less potent than oxybutynin, it has an effect profile that makes it of interest to test its ability to counteract bladder overactivity in humans.     

Functional role of central muscarinic receptors for micturition in normal conscious rats

PURPOSE: Antimuscarinic agents, which are used in to treat urgency and urge incontinence, have well-known effects on peripheral muscarinic receptors. However, some currently used drugs may have effects on muscarinic receptors in the brain and/or spinal cord involved in voiding control. We tested if muscarinic receptors within the central nervous system mediate a tonic excitatory influence on voiding in rats and if these receptors can be differently influenced by antimuscarinic drugs. MATERIALS AND METHODS: The effects on cystometrography of intracerebroventricular atropine, oxybutynin, tolterodine and darifenacin were investigated in normal conscious rats. RESULTS: Atropine (0.2 to 2 nmol.) dose dependently affected urodynamic parameters. At 2 nmol. in 6 rats the drug decreased voiding pressure (p <0.01), and increased bladder capacity (p <0.001), voided volume (p <0.05) and post-void residual volume (p <0.05). In 6 rats oxybutynin (6 to 40 nmol.) given at a dose of 6 nmol. caused no change in cystometric parameters, while at 20 nmol. the drug decreased voiding pressure (p <0.01). Tolterodine (2 to 20 nmol.) dose dependently changed urodynamic parameters, while at 20 nmol. in 6 rats the drug decreased voiding pressure (p <0.01) and increased bladder capacity (p <0.05) and voided volume (p <0.05). Darifenacin given at a dose of 20 nmol. in 6 rats caused no change in cystometric parameters. CONCLUSIONS: Muscarinic receptor mechanisms in the central nervous system mediate a tonic excitatory influence on voiding in rats, while nonsubtype selective antimuscarinic drugs may have an inhibitory effect on these mechanisms.     

Effect of muscarinic antagonists on micturition pressure measured by cystometry in normal,conscious rats

Objectives. To establish an in vivo model to screen new muscarinic antagonists for the treatment of overactive urinary bladder and to calculate the respective ID₅₀ values.Methods. The conscious rat cystometry model was modified to determine a complete dose-response curve in each animal. Spontaneous micturition was induced by infusion of room-temperature saline into rat bladders at a constant rate of 12 mL/hr. Cumulative doses of muscarinic antagonists administered in the femoral vein caused dose-dependent inhibition of the urinary bladder contraction measured as the micturition pressure. In addition, the in vitro pK_B values for atropine, PNU-200577 (DD01), tolterodine, oxybutynin, and terodiline were determined in carbachol-contracted rat bladder strips.Results. The rank order of the in vivo ID₅₀ values were atropine (14 ± 4 nmol/kg), PNU-200577 (22 ± 12 nmol/kg), tolterodine (94 ± 20 nmol/kg), oxybutynin (175 ± 89 nmol/kg), darifenacin (236 ± 144 nmol/kg), desethyloxybutynin (313 ± 209 nmol/kg), propiverine (4561 ± 2079 nmol/kg), and terodiline (18,339 ± 5348 nmol/kg). Tolterodine and PNU-200577 caused a parallel shift of the in vitro concentration-response curve to the right and did not alter the maximal contraction. The ID₅₀ values correlated significantly with the in vitro rat pK_B and human bladder pA₂ values.Conclusions. The present results suggest that the rat cystometry model can be used in in vivo screening for new muscarinic antagonists.     

Wie beeinflussen Medikamente zur Therapie der Harninkontinenz die Gehirnfunktion beim älteren Menschen?

Anticholinergic agents are used for treatment of overactive bladder syndrome (OAB) by competitve blockade of acetylcholine at the muscarinic receptor. At present five different subtypes of M-receptors can be differentiated. Primary detrusor effects are mediated by M3-receptors as are side effects like dry mouth and constipation. Cardiac and central nervous system side effects appear to be M2 or M1 related. OAB symptom relief by the unselective drugs tolterodine, oxybutynin or trospium chloride and by M3-selective agents like darifenacin or solifenacin seems to be rather similar. Central side effects are different depending on gastrointestinal reabsorption, serum metabolism and penetration of the blood-brain barrier. Slow release formulations may be better tolerated. Anticholinergics that penetrate the blood-brain barrier may cause cognitive imbalance in older patients, as recent studies have shown for oxybutynin. Here M3-selective agents may offer an advantage.     

How do medications used to treat urinary incontinence affect the cerebral function of the elderly?

Anticholinergic agents are used for treatment of overactive bladder syndrome (OAB) by competitive blockade of acetylcholine at the muscarinic receptor. At present five different subtypes of M-receptors can be differentiated. Primary detrusor effects are mediated by M3-receptors as are side effects like dry mouth and constipation. Cardiac and central nervous system side effects appear to be M2 or M1 related. OAB symptom relief by the unselective drugs tolterodine, oxybutynin or trospium chloride and by M3-selective agents like darifenacin or solifenacin seems to be rather similar. Central side effects are different depending on gastrointestinal reabsorption, serum metabolism and penetration of the blood-brain barrier. Slow release formulations may be better tolerated. Anticholinergics that penetrate the blood-brain barrier may cause cognitive imbalance in older patients, as recent studies have shown for oxybutynin. Here M3-selective agents may offer an advantage.     

Comparative efficacy and tolerability of solifenacin 5 mg/day versus other oral antimuscarinic agents in overactive bladder: A systematic literature review and network meta‐analysis

Aims

To compare efficacy and tolerability of solifenacin 5 mg/day versus other oral antimuscarinic agents for the treatment of overactive bladder (OAB).

Methods

Literature searches of MEDLINE, Embase, and the Cochrane Library were undertaken to identify randomized controlled trials in OAB (2000‐2015) for antimuscarinic agents. A network meta‐analysis (NMA) was performed to estimate efficacy and tolerability outcomes for solifenacin 5 mg/day relative to other antimuscarinics.

Results

The NMA included 53 eligible trials (published, n = 48; unpublished on search date, n = 5). Solifenacin 5 mg/day was significantly more effective than tolterodine 4 mg/day for reducing incontinence and urgency urinary incontinence (UUI) episodes, but significantly less effective than solifenacin 10 mg/day for micturition; no other statistically significant differences were noted for efficacy. Solifenacin 5 mg/day had a statistically significant lower risk of dry mouth compared with darifenacin 15 mg/day, fesoterodine 8 mg/day, oxybutynin extended‐release 10 mg/day, oxybutynin immediate‐release (IR) 9‐15 mg/day, tolterodine IR 4 mg/day, propiverine 20 mg/day, and solifenacin 10 mg/day. There were no significant differences between solifenacin 5 mg/day and other antimuscarinics for risk of blurred vision, or for 11 of 17 active comparators for risk of constipation.

Conclusions

This NMA suggests that the efficacy of solifenacin 5 mg/day is at least similar to other common antimuscarinics across the spectrum of OAB symptoms analyzed, and is more effective than tolterodine 4 mg/day in reducing incontinence and UUI episodes. Solifenacin 5 mg/day has a lower risk of dry mouth compared with several agents.

     

Which muscarinic receptor is important in the bladder?

Antimuscarinic agents are the most widely used therapy for urge incontinence, but have side effects such as constipation, tachycardia and dry mouth, resulting from a lack of selectivity for the bladder. M₂ receptors are the predominant cholinoceptors present in urinary bladder, but mainly the minor population of M₃ receptors mediate its contraction. M₂ receptors modulate detrusor contraction by several mechanisms, and may contribute more to contraction of the bladder in pathological states such as bladder denervation or spinal cord injury. Prejunctional inhibitory M₂ or M₄ receptors and prejunctional facilitatory muscarinic M₁ receptors in the bladder have all been reported. In clinical studies, tolterodine, a non-selective muscarinic antagonist, has been reported to be as effective as oxybutynin but inducing less dry mouth. Thus, although it is not certain which antimuscarinic drugs have the better efficacy and tolerability, the non-selective antimuscarinic drugs seem to be better than M₃-selective antagonists in their clinical efficacies. However, controlled release, or intravesical, intravaginal, or rectal administrations of oxybutynin have been reported to cause fewer side effects. Darifenacin, a new M₃ selective antagonist, has been reported to have selectivity for the bladder over the salivary gland in vivo. To verify which antimuscarinic drugs selective for the muscarinic subtypes have the best efficacy and tolerability, comparative clinical trials between M₃ selective antagonists and non-selective compounds, such as olterodine, are required in the future.     

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.     

Identification of muscarinic receptor subtypes of cultured smooth muscle cells and tissue of human bladder body

BACKGROUND: Muscarinic receptor subtypes of cultured smooth muscle cells from the human bladder body were investigated by the receptor binding assay method. The result was compared with that obtained from the human bladder body tissue to confirm whether the receptor subtypes of the cells are not changed after several passages of cell culture. METHODS: Inhibitory effects of various muscarinic antagonists on the binding of [3H]-N-methylscopolamine ([3H]-NMS) to membrane preparations obtained from cultured smooth muscle cells from the fourth subculture of the human bladder body were compared with those prepared from the human bladder body tissue and cells expressing human muscarinic receptor subtypes. RESULTS: Binding-inhibition constants (pKi) for atropine, pirenzepine, methoctramine, 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP), oxybutynin and propiverine obtained from membrane preparations of cultured smooth muscle cells were 8.91, 6.35, 8.24, 8.53, 7.29 and 5.61, respectively. pKi values of these muscarinic receptor antagonists against the membrane preparation of human bladder body tissue were 9.08, 6.66, 8.05, 8.79, 7.53 and 6.04, respectively. pKi values of cultured smooth muscle cells and tissue from human bladder body were correlated closely with those of insect cells expressing the cloned human M2 receptor subtype. CONCLUSION: The binding affinities for various muscarinic receptor antagonists of cultured human smooth muscle cells were maintained through the fourth subculture and it was suggested that the M2 receptor subtype is predominantly expressed in cultured smooth muscle cells of human bladder body as well as in tissue of the human bladder body.     

THE COST‐EFFECTIVENESS OF SOLIFENACIN VS FESOTERODINE,OXYBUTYNIN IMMEDIATE‐RELEASE,PROPIVERINE, TOLTERODINE EXTENDED‐RELEASE AND TOLTERODINE IMMEDIATE‐RELEASE IN THE TREATMENT OF PATIENTS WITH OVERACTIVE BLADDER IN THE UK NATIONAL HEALTH SERVICE

OBJECTIVE

Please also see BJUI letters on page 586 To assess the cost‐effectiveness of solifenacin vs other antimuscarinic strategies commonly used in UK clinical practice, based on the results of a recent published review.

METHODS

Overactive bladder (OAB) syndrome is characterized by symptoms of urgency, frequency, incontinence and nocturia. Pharmacological treatment comprises oral antimuscarinic agents, which are divided into older‐generation treatments, including oxybutynin, and new‐generation treatments, comprising solifenacin, tolterodine, darifenacin and fesoterodine. The latter have reduced central nervous system penetration and have better selectivity for the M3 subclass of acetylcholine receptors, resulting in improved tolerability. A recent systematic review and meta‐analysis of the efficacy and safety of antimuscarinics provided an opportunity for an economic evaluation of these agents using a rigorous assessment of efficacy. A cost‐utility analysis was undertaken using a 1‐year decision‐tree model. Treatment success was defined separately for urgency, frequency and incontinence, with efficacy data taken from the recent review. Treatment persistence rates were taken from the Information Management System database. Utility values for the calculation of quality‐adjusted life‐years (QALYs) were taken from published sources. The analysis included costs directly associated with treatment for OAB, i.e. antimuscarinic therapy, consultations with general practitioners, and outpatient contacts. Resource use was based on expert opinion. Costs were reported at 2007/2008 prices. Extensive deterministic and probabilistic analyses were conducted to test the robustness of the base‐case results.

RESULTS

Solifenacin was associated with the highest QALY gains (per 1000 patients) for all three outcomes of interest, i.e. urgency (712.3), frequency (723.1) and incontinence (695.0). Solifenacin was dominant relative to fesoterodine, tolterodine extended‐release (ER) and tolterodine immediate‐release (IR), and cost‐effective relative to propiverine ER for urgency, frequency and incontinence. Solifenacin was not found to be cost‐effective relative to oxybutynin IR for the frequency and incontinence outcomes, with an incremental cost‐effectiveness ratio of >£30 000/QALY threshold.

CONCLUSIONS

Solifenacin provided the greatest clinical benefit and associated QALYs for all three outcomes of interest across all therapies considered, and to be either dominant or cost‐effective relative to all other new‐generation agents, but not cost‐effective relative to oxybutynin for frequency and incontinence.     

Comparison of the efficacy, safety, and tolerability of propiverine and oxybutynin for the treatment of overactive bladder syndrome

AIM: To compare the effects of propiverine and oxybutynin on ambulatory urodynamic monitoring (AUM) parameters, safety, and tolerability in patients with overactive bladder. METHODS: This was a randomized, double-blind, placebo-controlled, multicentre, crossover study. Patients (n = 77) received two of the following treatments during two 2-week periods: propiverine 20 mg once daily, propiverine 15 mg three times daily, oxybutynin 5 mg three times daily, and placebo. AUM parameters, salivary flow, visual near point, and heart rate were assessed. RESULTS: A consistent order in the efficacy between active treatment groups was observed for the reduction in mean involuntary detrusor contractions (IDCs; oxybutynin 15 mg 相似文献   

Propiverine vs oxybutynin for treating neurogenic detrusor overactivity in children and adolescents: results of a multicentre observational cohort study

OBJECTIVE

To compare, in a retrospective observational cohort study, the efficacy, tolerability, safety and clinical effectiveness of propiverine and oxybutynin in children and adolescents with neurogenic detrusor overactivity (NDO).

PATIENTS AND METHODS

In all, 255 children and adolescents (aged 1–18 years) with NDO (199 myelomeningocele, 46 spinal cord injury, 10 other diagnoses) were enrolled at 14 study centres. To evaluate the efficacy of propiverine and oxybutynin, urodynamic and clinical variables were assessed before and after at least 12 month of the antimuscarinic agents administered at variable doses.

RESULTS

In all, 127 patients given propiverine and 128 given oxybutynin were enrolled. The primary efficacy outcome, i.e. reductions in urodynamically assessed individual maximum detrusor pressure (P_detmax), was assumed to indicate success in 74.2% of those on propiverine vs 49.6% on oxybutynin. The mean P_detmax was significantly reduced during treatment, from 59.8 to 36.7 cmH₂O in the propiverine and from 65.2 to 54.9 cmH₂O in the oxybutynin groups. The mean maximum cystometric bladder capacity increased from 146 to 242 mL in the propiverine and from 222 to 310 mL in the oxybutynin group. Propiverine was better tolerated than oxybutynin, having fewer adverse drug reactions (9.4% vs 17.2%, odds ratio 2.04), and for its severity grades and premature treatment termination (none vs 11 cases).

CONCLUSION

In this non‐interventional study, reflecting ‘real‐life’ clinical practice, comparing the efficacy, tolerability and safety of propiverine and oxybutynin in children and adolescents with NDO, propiverine was at least as effective as oxybutynin, but better tolerated, resulting in superior clinical effectiveness than for oxybutynin.     

Intravesical instillation of human urine after oral administration of trospium, tolterodine and oxybutynin in a rat model of detrusor overactivity

OBJECTIVE: To study the effects of antimuscarinics excreted into human urine on normal bladder in a rat model of detrusor overactivity. MATERIALS AND METHODS: Two 'normal' adult volunteers collected voided urine after taking trospium (20 mg, twice daily), tolterodine LA (4 mg, four times daily), or oxybutynin XL (10 mg, four times daily). The drugs were taken in a random order for 5 days with a 7-day washout period between the drugs. The urine collected from the two volunteers was mixed together and then blindly labelled and used for testing. Control human urine (no oral antimuscarinics) was also used. The effect of intravesical administration of human urine on carbachol-induced bladder overactivity was studied in female Sprague-Dawley rats anaesthetised with urethane. Cystometric variables during continuous infusion (0.04 mL/min) for >1 h each of saline, human urine, then a mixture of carbachol (30 microm) and human urine were compared in the four groups (control and the three different antimuscarinics tested; six rats per group). RESULTS: Human urine, with or with no intake of antimuscarinic agents, had no effect on normal bladder function. Bladder capacity and intercontraction intervals were significantly decreased after adding carbachol to urine containing vehicle, tolterodine or oxybutynin. However, urine collected from the humans who had taken trospium prevented the carbachol-induced reduction in bladder capacity and intercontraction intervals. Maximum voiding pressure and pressure threshold were not changed in any case. CONCLUSION: This is the first report that the urine excreted after oral ingestion of trospium (20 mg, twice daily) has a significant inhibitory effect in a rat model of detrusor overactivity. This suggests that antimuscarinic agents have a local bladder effect during the bladder-storage phase in addition to the smooth muscle-mediated voiding phase.     

Once-daily, extended-release formulations of antimuscarinic agents in the treatment of overactive bladder: a review

Overactive bladder (OAB) is a chronic condition that often requires long-term treatment to maintain control of symptoms. A range of therapeutic options are available; however, antimuscarinic agents form the mainstay of treatment. Of these agents, tolterodine and oxybutynin are the most widely used. It is well documented that the immediate-release (IR) formulations of these agents have equivalent efficacy in relieving OAB symptoms. However, tolterodine demonstrates a more favorable tolerability profile, particularly in terms of the frequency and severity of dry mouth. Due to the development of novel drug delivery systems, extended-release (ER) formulations of both oxybutynin and tolterodine are now available, permitting once-daily dosing. The convenience of once-daily dosing of antimuscarinic agents would be expected to improve patient compliance and further relieve the symptoms of OAB. Clinical studies with the ER formulations of tolterodine and oxybutynin demonstrate potential clinical advantages over their respective IR forms in terms of either efficacy or tolerability or both, although the therapeutic index of tolterodine ER appears to show a greater advantage over its IR counterpart compared with oxybutynin ER and its IR form. Importantly, the two ER agents have not been compared directly in a head-to-head clinical study. Overall, available clinical data suggest that the newly developed ER formulation of tolterodine represents a significant therapeutic advancement in the treatment of OAB.     

Treatment of overactive bladder with modified intravesical oxybutynin chloride

Intravesical oxybutynin chloride has been reported to be effective for overactive bladder, although sometimes the efficacy does not last long enough. To improve this deficiency, we report the effects of intravesical oxybutynin chloride with hydroxypropylcellulose (modified intravesical oxybutynin). Modified intravesical oxybutynin (5 mg/10 mL, twice a day) was administered to six overactive bladder patients for more than 1 year (two men and four women; average age, 56.5 years) who did not respond to oral anticholinergic agents and electric stimulation. Cystometography (CMG) was performed before, 2 hours, and 1 week after the start of modified intravesical oxybutynin. In addition, plasma levels of oxybutynin and its active metabolite, N-desethyl-oxybutynin (DEOB), were measured by high-performance liquid chromatography before, 1, 2, and 4 hours after the initial treatment of modified intravesical oxybutynin. CMG studies revealed that two of the six patients did not demonstrate uninhibited contractions 1 week after the treatment and that cystocapacity of before, 2 hours, and 1 week after the initial modified intravesical oxybutynin was 141.8+/-15.3, 210.0+/-35.5, and 305.0+/-21.3 mL, respectively. Plasma levels of oxybutynin and DEOB before, 1, 2, and 4 hours after the first instillation of modified intravesical oxybutynin were oxybutynin; not detected, 8.8+/-2.5, 6.8+/-1.1, 3.0+/- 1.0 ng/ml, and DEOB; not detected, 4.2+/-1.3, 6.4+/-1.7, 5.1+/- 1.4 ng/ml, respectively. No side effects were observed in any of the patients. Modified intravesical oxybutynin is an effective and safe therapy option for overactive bladder patients who do not respond to other treatments such as oral anticholinergic agents and electric stimulation.     

Pharmacological characterization of a novel investigational antimuscarinic drug, fesoterodine, in vitro and in vivo

OBJECTIVE

To investigate the primary pharmacology of fesoterodine (a novel antimuscarinic drug developed for treating overactive bladder) and SPM 7605 (its active metabolite, considered to be the main pharmacologically active principle of fesoterodine in man) against human muscarinic receptor subtypes, and to investigate in vitro and in vivo functional activity of these agents on the rat bladder compared with existing standard agents.

MATERIALS AND METHODS

The displacement of radioligand binding by fesoterodine, SPM 7605 and standard agents in membrane preparations of Chinese hamster ovary (CHO) cells expressing the different human muscarinic receptors (M1–M5) was characterized. Agonistic and antagonistic activities were studied using different CHO cell lines stably expressing the human recombinant muscarinic receptor subtypes. The effects of fesoterodine and SPM 7605 on isolated bladder strips contracted by carbachol or electrical field stimulation (EFS) were investigated. In vivo the effects of fesoterodine and SPM 7605 on micturition variables were assessed using continuous cystometry in conscious female Sprague‐Dawley rats, and compared to those of oxybutynin and atropine.

RESULTS

In vitro SPM 7605 potently inhibited radioligand binding at all five human muscarinic receptor subtypes with equal affinity across all five. Fesoterodine had a similar balanced selectivity profile but was less potent than SPM 7605. Both substances were competitive antagonists of cholinergic agonist‐stimulated responses in human M1‐M5 cell lines and had a similar potency and selectivity profile to the radioligand‐binding studies. In rat bladder strips, fesoterodine and SPM 7605 caused a rightward shift of the concentration‐response curve for carbachol with no depression of the maximum, and concentration‐dependently reduced contractions induced by EFS. The potency of both drugs was similar to that of atropine and oxybutynin. In the presence of the esterase inhibitor neostigmine, the concentration‐response curve of fesoterodine was shifted to the right, suggesting that part of the activity was caused by metabolism to SPM 7605 by tissue enzymes. In vivo, low doses (0.01 mg/kg) of fesoterodine and SPM 7605 reduced micturition pressure and increased intercontraction intervals and bladder capacity, but did not affect residual volume.

CONCLUSIONS

Fesoterodine and its active metabolite, SPM 7605, are nonsubtype selective, competitive antagonists of human muscarinic receptors, but SPM 7605 has greater potency than the parent compound. Pharmacodynamic studies in the rat bladder in vitro confirm the competitive muscarinic antagonist profile of these agents in a native tissue preparation, and in vivo studies in the rat showed effects on bladder function consistent with a muscarinic antagonist profile.