Pharmacodynamics of propiverine and three of its main metabolites on detrusor contraction

Comparisons of urinary bladder responses to common antimuscarinics reveals unique effects of darifenacin

Introduction

Antimuscarinics are the first-line pharmaceutical treatment for overactive bladder (OAB). However, some literature suggests that responses to these antimuscarinics can influence a variety of non-muscarinic receptors. This study aimed to identify any non-muscarinic influences on contraction from commonly prescribed clinical antimuscarinics using porcine detrusor or urothelium with lamina propria (U&LP) tissues.

Methods

Porcine bladders were dissected into strips of juvenile or adult detrusor or U&LP. Carbachol concentration-response curves were performed on paired tissues in the absence or presence of commonly prescribed antimuscarinics: darifenacin, fesoterodine, oxybutynin, solifenacin, trospium, and tolterodine. Estimated affinities for each antimuscarinic were calculated, and maximum contraction values from control and intervention curves were compared. Experiments in the presence of darifenacin (100 nM) were completed with serotonin (100 µM), prostaglandin E2 (10 µM), histamine (100 µM), αβ-methylene-ATP (10 µM), angiotensin II (100 nM), neurokinin A (300 nM), and carbachol (10 µM).

Results

Darifenacin significantly reduced maximum contraction responses to carbachol in adult detrusor preparations by 46%, αβ-methylene-ATP by 50%, prostaglandin E2 by 73%, histamine by 64%, and serotonin by 53%. Darifenacin reduced the maximum contraction in adult U&LP preparations to carbachol by 49% and to αβ-methylene-ATP by 35%.

Discussion

Darifenacin presents as an antimuscarinic medication that influences non-muscarinic pathways in urinary bladder tissue, indicating its potential to assist OAB patients with non-muscarinic pathophysiology.

Effects of Microbeam Irradiation on Rodent Esophageal Smooth Muscle Contraction

BACKGROUND

High-dose-rate radiotherapy has shown promising results with respect to normal tissue preservation. We developed an ex vivo model to study the physiological effects of experimental radiotherapy in the rodent esophageal smooth muscle.

METHODS

We assessed the physiological parameters of the esophageal function in ex vivo preparations of the proximal, middle, and distal segments in the organ bath. High-dose-rate synchrotron irradiation was conducted using both the microbeam irradiation (MBI) technique with peak doses greater than 200 Gy and broadbeam irradiation (BBI) with doses ranging between 3.5-4 Gy.

RESULTS

Neither MBI nor BBI affected the function of the contractile apparatus. While peak latency and maximal force change were not affected in the BBI group, and no changes were seen in the proximal esophagus segments after MBI, a significant increase in peak latency and a decrease in maximal force change was observed in the middle and distal esophageal segments.

CONCLUSION

No severe changes in physiological parameters of esophageal contraction were determined after high-dose-rate radiotherapy in our model, but our results indicate a delayed esophageal function. From the clinical perspective, the observed increase in peak latency and decreased maximal force change may indicate delayed esophageal transit.

Factors Associated with Decisions for Initial Dosing, Up-Titration of Propiverine and Treatment Outcomes in Overactive Bladder Syndrome Patients in a Non-Interventional Setting

Two doses of propiverine ER (30 and 45 mg/d) are available for the treatment of overactive bladder (OAB) syndrome. We have explored factors associated with the initial dosing choice (allocation bias), the decision to adapt dosing (escalation bias) and how dosing relative to other factors affects treatment outcomes. Data from two non-interventional studies of 1335 and 745 OAB patients, respectively, receiving treatment with propiverine, were analyzed post-hoc. Multivariate analysis was applied to identify factors associated with dosing decisions and treatment outcomes. Several parameters were associated with dose choice, escalation to higher dose or treatment outcomes, but only few exhibited a consistent association across both studies. These were younger age for initial dose choice and basal number of urgency and change in incontinence episodes for up-titration. Treatment outcome (difference between values at 12 weeks vs. baseline) for each OAB system was strongly driven by the respective baseline value, whereas no other parameter exhibited a consistent association. Patients starting on the 30 mg dose and escalating to 45 mg after 4 weeks had outcomes comparable with those staying on a starting dose of 30 or 45 mg. We conclude that dose escalation after 4 weeks brings OAB patients with an initially limited improvement to a level seen in initially good responders. Analysis of underlying factors yielded surprisingly little consistent insight.

A Novel in situ Approach to Studying Detrusor Smooth Muscle Cells in Mice

The aim of our study was to develop a novel approach to investigating mouse detrusor smooth muscle cell (SMC) physiological activity, utilizing an acute tissue dissection technique and confocal calcium imaging. The bladder of a sacrificed adult female NMRI mouse was dissected. We used light and transmission electron microscopy to assess morphology of SMCs within the tissue. Calcium imaging in individual SMCs was performed using confocal microscopy during stimulation with increasing concentrations of carbamylcholine (CCh). SMCs were identified according to their morphology and calcium activity. We determined several parameters describing the SMC responses: delays to response, recruitment, relative activity, and contraction of the tissue. CCh stimulation revealed three different SMC phenotypes: spontaneously active SMCs with and without CCh-enhanced activity and SMCs with CCh-induced activity only. SMCs were recruited into an active state in response to CCh-stimulation within a narrow range (1-25 µM); causing activation of virtually all SMCs. Maximum calcium activity of SMCs was at about 25 µM, which coincided with a visible tissue contraction. Finally, we observed shorter time lags before response onsets with higher CCh concentrations. In conclusion, our novel in situ approach proved to be a robust and reproducible method to study detrusor SMC morphology and physiology.

Results of a randomized, double-blind, active-controlled clinical trial with propiverine extended release 30 mg in patients with overactive bladder

OBJECTIVE

To compare the efficacy and safety of the 30 mg extended release (ER) formulation of propiverine hydrochloride with the 4 mg ER formulation of tolterodine tartrate in patients with overactive bladder (OAB) in a non-inferiority trial.

PATIENTS AND METHODS

Eligible patients, aged 18-75 years and with symptoms of OAB, were enrolled in this multicentre, randomized, double-blind, parallel-group, active-controlled study. After a 2-week screening period, patients were randomized at a 1:1 ratio to receive either propiverine ER 30 mg or tolterodine ER 4 mg daily during the 8-week treatment period. Efficacy was assessed using a 3-day voiding diary and patient's self-reported assessment of treatment effect. Safety assessment included recording of adverse events, laboratory test results, measurement of post-void residual urine and electrocardiograms.

RESULTS

A total of 324 patients (244 female and 80 male) were included in the study. Both active treatments improved the variables included in the voiding diary and in the patient's self-reported assessment. The change from baseline in the number of voidings per 24 h was significantly greater in the propiverine ER 30 mg group compared with the tolterodine ER 4 mg group after 8 weeks of treatment (full analysis set [FAS] -4.6 ± 4.1 vs -3.8 ± 5.1; P = 0.005). Significant improvements were also observed for the change of urgency incontinence episodes after 2 weeks (P = 0.026) and 8 weeks (P = 0.028) of treatment when comparing propiverine ER 30 mg with tolterodine ER 4 mg. Both treatments were well tolerated, with a similar frequency of adverse drug reactions in both the propiverine ER 30 mg and tolterodine ER 4 mg groups (FAS 40.7 vs 39.5%; P = 0.8). More patients treated with tolterodine ER 4 mg discontinued the treatment because of adverse drug reactions compared with propiverine ER 30 mg (7.4 vs 3.1%).

CONCLUSIONS

Propiverine ER 30 mg was confirmed to be an effective and well-tolerated treatment option for patients with OAB symptoms. This first head-to-head study showed non-inferiority of propiverine ER 30 mg compared with tolterodine ER 4 mg.

Selectivity of pharmacological tools: implications for use in cell physiology. A review in the theme: Cell signaling: proteins, pathways and mechanisms

Pharmacological inhibitors are frequently used to identify the receptors, receptor subtypes, and associated signaling pathways involved in physiological cell responses. Based on the effects of such inhibitors conclusions are drawn about the involvement of their assumed target or lack thereof. While such inhibitors can be useful tools for a better physiological understanding, their uncritical use can lead to incorrect conclusions. This article reviews the concept of inhibitor selectivity and its implication for cell physiology. Specifically, we discuss the implications of using inhibitor vs. activator approaches, issues of direct vs. indirect pathway modulation, implications of inverse agonism and biased signaling, and those of orthosteric vs. allosteric, competitive vs. noncompetitive, and reversible vs. irreversible inhibition. Additional problems can result from inconsistent estimates of inhibitor potency and differences in potency between cell-free systems and intact cells. These concepts are illustrated by several examples of inhibitors displaying affinity for related but distinct targets or even unrelated targets. Of note, many of the issues being addressed are also applicable to genetic inhibition strategies. The main practical conclusion following from these concepts is that investigators should be critical in the choice of inhibitor, its concentrations, and its mode of application. When this advice is adhered to, small-molecule pharmacological inhibitors can be important experimental tools in the hand of physiologists.

Age-dependent contribution of Rho kinase in carbachol-induced contraction of human detrusor smooth muscle in vitro

AIM

Activation of muscarinic receptors on the detrusor smooth muscle is followed by contraction, which involves both myosin light chain kinase (MLCK) and Rho kinase (ROCK). The aim of this study was to determine the relative contributions of MLCK and ROCK to carbachol-induced contraction of human detrusor smooth muscle in vitro.

METHODS

Detrusor smooth muscle strips were prepared from the macroscopically unaffected bladder wall of patients underwent cystectomy. The strips were fixed in an organ bath, and carbachol or KCl-induced isometric contractions were measured by force transducers.

RESULTS

Addition of carbachol (0.4-4 μmol/L) into the bath induced concentration-dependent contractions of detrusor specimens, which was completely abolished by atropine (1 μmol/L). Pre-incubation of detrusor specimens with either the MLCK inhibitor ML-9 or the ROCK inhibitors HA1100 and Y-27632 (each at 10 μmol/L) significantly blocked carbachol-induced contractions as compared to the time-control experiments. Moreover, MLCK and ROCK inhibition were equally effective in reducing carbachol-induced contractions. The residual carbachol-induced contractions in the presence of both MLCK and ROCK inhibitors were significantly smaller than the contractions obtained when only one enzyme (either MLCK or ROCK) was inhibited, suggesting an additive effect of the two kinases. Interestingly, ROCK-mediated carbachol-induced contractions were positively correlated to the age of patients (r=o.52, P<0.05).

CONCLUSION

Both MLCK and ROCK contribute to carbachol-induced contractions of human detrusor smooth muscle. ROCK inhibitors may be a new pharmacological approach to modulate human bladder hyperactivity.

Propiverine: a review of its use in the treatment of adults and children with overactive bladder associated with idiopathic or neurogenic detrusor overactivity, and in men with lower urinary tract symptoms

Propiverine is a well established antimuscarinic agent with a mixed mode of action in the treatment of symptoms associated with overactive bladder (OAB). As well as blocking muscarinic receptors in the detrusor muscle, the drug also inhibits cellular calcium influx, thereby diminishing muscle spasm. In patients with symptoms of OAB resulting from idiopathic detrusor overactivity (IDO) or neurogenic detrusor overactivity (NDO), propiverine demonstrated dose-dependent efficacy and tolerability, with adverse events consistent with those associated with all antimuscarinic agents. In adults with IDO, propiverine demonstrated similar efficacy to that of other antimuscarinic agents (including solifenacin, tolterodine, oxybutynin and imidafenacin) and, in adults with NDO, propiverine and oxybutynin demonstrated similar efficacy. Propiverine was generally well tolerated in these patient populations, with a lower incidence of dry mouth than that associated with oxybutynin. In men with lower urinary tract symptoms (LUTS), and in whom the presence of benign prostatic enlargement (BPE) was implicated, propiverine administered as add-on therapy to an α(1)-adrenoceptor antagonist demonstrated similar or superior efficacy to that achieved with an α(1)-adrenoceptor antagonist alone, and combination therapy was particularly effective in patients with urinary storage symptoms. Combination therapy was generally well tolerated, but was associated with a higher incidence of adverse events than an α(1)-adrenoceptor antagonist alone. In children and adolescents with IDO/OAB or NDO, propiverine was generally more effective and better tolerated than oxybutynin. In conclusion, propiverine provides a valuable option for the treatment of adults and children with OAB associated with IDO or NDO, and in men with storage LUTS.

Functional investigation of β-adrenoceptors in human isolated detrusor focusing on the novel selective β3-adrenoceptor agonist KUC-7322

This study aimed to characterize the β-adrenoceptor (β-AR) subtype mediating relaxation of isolated human bladder strips and to explore relaxation by the novel β3-AR-selective agonist KUC-7322 for its relaxant effect on the human isolated detrusor and for its effect on the carbachol (CCh)-induced contractile response. In two parallel studies, relaxation of isolated human bladder strips was tested for the β-AR agonists isoproterenol, clenbuterol, BRL 37344, and KUC-7322. For the isoproterenol and KUC-7322 responses, antagonism by CGP 20712A, ICI 118551, and SR59230A was determined. The potency and efficacy of the reference agonists for detrusor relaxation was in line with their known β3-AR activity. KUC-7322 relative to isoproterenol was a full agonist with a pEC(50) of 5.95 ± 0.09 and 5.92 ± 0.11 in the two studies. SR59230A exhibited antagonism of the expected potency against isoproterenol (apparent pK (B) 7.2) but not against KUC-7322. Neither isoproterenol nor KUC-7322 nor forskolin significantly attenuated CCh-induced contraction. These results suggest that KUC-7322 displays full agonistic activity in relaxing the human detrusor without inhibiting the contraction induced by cholinergic stimulation. These characteristics, if proven in vivo, may be beneficial for the treatment of overactive bladder, as increased bladder capacity with a negligible effect on voiding contractions may be anticipated.

The muscarinic receptor antagonist propiverine exhibits α(1)-adrenoceptor antagonism in human prostate and porcine trigonum

Purpose

Combination therapy of male lower urinary tract symptoms with α₁-adrenoceptor and muscarinic receptor antagonists attracts increasing interest. Propiverine is a muscarinic receptor antagonist possessing additional properties, i.e., block of L-type Ca²⁺ channels. Here, we have investigated whether propiverine and its metabolites can additionally antagonize α₁-adrenoceptors.

Methods

Human prostate and porcine trigone muscle strips were used to explore inhibition of α₁-adrenoceptor-mediated contractile responses. Chinese hamster ovary (CHO) cells expressing cloned human α₁-adrenoceptors were used to determine direct interactions with the receptor in radioligand binding and intracellular Ca²⁺ elevation assays.

Results

Propiverine concentration-dependently reversed contraction of human prostate pre-contracted with 10 μM phenylephrine (−log IC₅₀ [M] 4.43 ± 0.08). Similar inhibition was observed in porcine trigone (−log IC₅₀ 5.01 ± 0.05), and in additional experiments consisted mainly of reduced maximum phenylephrine responses. At concentrations ≥1 μM, the propiverine metabolite M-14 also relaxed phenylephrine pre-contracted trigone strips, whereas metabolites M-5 and M-6 were ineffective. In radioligand binding experiments, propiverine and M-14 exhibited similar affinity for the three α₁-adrenoceptor subtypes with −log K_i [M] values ranging from 4.72 to 4.94, whereas the M-5 and M-6 did not affect [³H]-prazosin binding. In CHO cells, propiverine inhibited α₁-adrenoceptor-mediated Ca²⁺ elevations with similar potency as radioligand binding, again mainly by reducing maximum responses.

Conclusions

In contrast to other muscarinic receptor antagonists, propiverine exerts additional L-type Ca²⁺-channel blocking and α₁-adrenoceptor antagonist effects. It remains to be determined clinically, how these additional properties contribute to the clinical effects of propiverine, particularly in male voiding dysfunction.

Efficacy of propiverine ER with or without α-blockers related to maximum urinary flow rate in adult men with OAB: results of a 12-week, multicenter, non-interventional study

Purpose

Comparison of efficacy of propiverine extended release (ER) 30 mg o.d. in the treatment of male OAB administered as monotherapy (MT) or add-on to α-blockers (combination treatment, CT) in relation to maximum urinary flow (Q_max) in a non-interventional study.

Methods

Men ≥40 years with OAB symptoms, Q_max ≥10 ml/s, prostate volume <40 ml, post-void residuals (PVR) <100 ml, and IPSS <20 were included. OAB symptoms, IPSS, and PVR were recorded before and after 12 weeks of treatment. Participants were stratified by Q_max (group A ≥15 ml/s, group B <15 ml/s) and CT vs. MT. Safety parameters were monitored.

Results

A total of 2,219 men participated and were involved in safety analysis; 1,849 men (mean age 66 years) fulfilled the inclusion criteria and were involved in efficacy analysis. In group A, 291 men received MT and 479 CT; in group B, 184 men received MT and 895 CT. OAB symptoms improved significantly in all groups throughout the study without differences between MT and CT. IPSS improvement in group B was less with MT than with CT (−3.9 vs. −5.2; P < 0.001), whereas IPSS improvement was similar in group A (−4.6 vs. −5.1). Mean PVR change was not clinically relevant, but two men (0.1%) experienced urinary retention.

Conclusions

Under real-life conditions, treatment of OAB symptoms with propiverine ER is equally effective in men with MT or CT regardless of baseline Q_max. In men with reduced Q_max, IPSS improvement is significantly smaller with MT. The incidence of urinary retention during propiverine ER treatment is low.

Efficacy and Safety of Propiverine and Solifenacin for the Treatment of Female Patients with Overactive Bladder: A Crossover Study

OBJECTIVES

To evaluate the clinical efficacy and tolerability of propiverine and solifenacin in female patients with overactive bladder (OAB).

METHODS

A prospective nonrandomized crossover study of propiverine 20 mg and solifenacin 5 mg was conducted. Female OAB patients were assigned alternately to treatment with propiverine for 8 weeks then solifenacin for 8 weeks (Group P-S) or solifenacin for 8 weeks then propiverine for 8 weeks (Group S-P). At baseline, 8th week and 16th week, symptoms were assessed using overactive bladder symptom score (OABSS).

RESULTS

A total of 121 patients were enrolled. Overall, 38 patients (31.4%) discontinued or dropped out and 83 patients were available for analysis (39 in Group P-S and 44 in Group S-P). In both groups, the total score and each score of OABSS were significantly improved after 8 weeks compared with baseline. In only Group P-S (changing over from propiverine to solifenacin), urgency score in the 16th week was further improved significantly compared with the 8th week. The most bothersome symptom at baseline was urgency incontinence (50.6%), followed by urgency (37.3%). Even after symptom improvement, more than half of the patients were bothered by urgency or urgency incontinence. The incidence of adverse events of moderate and severe grade was higher during propiverine treatment than solifenacin (11.1% vs 2.9%, P = 0.039).

CONCLUSION

Propiverine 20 mg and solifenacin 5 mg were effective for treating female OAB patients. Urgency was further improved after switching from propiverine to solifenacin, but not after switching from solifenacin to propiverine. Solifenacin was better tolerated than propiverine.

The N-oxide metabolite contributes to bladder selectivity resulting from oral propiverine: muscarinic receptor binding and pharmacokinetics

We characterized contribution of N-oxide metabolites [1-methyl-4-piperidyl diphenylpropoxyacetate N-oxide (M-1) and 1-methyl-4-piperidyl benzilate N-oxide (M-2)] to the binding of muscarinic receptors in relation to the pharmacokinetics of propiverine in rats. The in vitro muscarinic receptor binding activity of M-2 was equipotent to that of propiverine, whereas M-1 was much less active. After the oral administration of propiverine (24.8-248 micromol/kg), there was relatively selective and longer-lasting binding of muscarinic receptors in the rat bladder compared with the submaxillary gland as shown by a significant increase in the apparent dissociation constant (K(d)) for specific binding of [N-methyl-(3)H]scopolamine ([(3)H]NMS). In addition, the intravesical instillation of M-2 produced a significant increase in K(d) for specific [(3)H]NMS binding in the rat bladder. Extremely high concentrations of M-1 and M-2 were detected in plasma after the oral administration of propiverine. The concentration of unbound M-2 was much higher than that of M-1 and propiverine in the rat plasma. The sum of maximal plasma unbound propiverine equivalents (C(max)) after the oral administration of propiverine at doses of 24.8, 74.3, and 248 micromol/kg was 66.0, 303, and 509 nM, respectively. The sum of corresponding area under the time-concentration curve from 0 to 12 h was 194, 2123, and 4645 nM . h, respectively. In fact, the unbound concentration of M-2 comprised more than 90% of sum of unbound propiverine equivalents in the plasma. After oral treatment with propiverine, the bladder showed the highest concentration of M-2, indicating specific distribution of this metabolite into the target organ. Thus, M-2 may contribute greatly to the relatively selective and long-lasting occupation of bladder muscarinic receptors after oral administration of propiverine.

Anticholinergic effects of cis- and trans-isomers of two metabolites of propiverine

The muscarinic receptor antagonist propiverine used for therapy of overactive bladder undergoes first pass metabolism, leading to several active metabolites, which affect muscarinic receptors and L-type Ca(2+) channels with different potencies. M-5, the major metabolite in blood, and M-6 can be synthesized as cis- and trans-isomers. We systematically investigated the pharmacodynamic profiles of the isomers on detrusor contractile function. In murine and porcine detrusor, the effects of the derivatives were examined on contractions induced by electric field stimulation (EFS), cumulatively increasing concentrations of carbachol or high KCl concentration. EFS contractions were concentration-dependently reduced by the M-5 and M-6 isomers although to a different extent. M-5(cis) was slightly more potent than M-5(trans), but the differences did not reach statistical significance. M-6(cis) was significantly more potent than M-6(trans). Responses to carbachol were antagonized by all compounds due to rightward shifts of the concentration-response curves, but only M-5(trans) also significantly reduced the maximum response. pK (B) values obtained with Schild plot analysis indicated slightly higher potency for M-6(cis) than M-6(trans). Ca(2+) influx-dependent contractions elicited by K(+) depolarization were less impaired by low concentrations of the M-6 isomers, but strongly suppressed by 100 microM of the M-5 isomers, suggesting an additional effect of the two M-5 isomers on Ca(2+) influx. All investigated isomers of M-5 and M-6 are biologically active in reducing detrusor contraction in animal tissue. While M-5( cis,) M-6(cis), and M-6(trans) possess surmountable or partially surmountable antagonistic properties at muscarinic receptors, M-5(trans) is a strong non-competitive antagonist. However, at higher concentration ranges, all four compounds seem to have additional effects on Ca(2+) influx.

Human urinary bladder smooth muscle is dependent on membrane cholesterol for cholinergic activation

Voiding is mediated by muscarinic receptors in urinary bladder smooth muscle cells. Lipid rafts and caveolae are cholesterol enriched membrane domains that modulate the activity of G protein-coupled receptors and second messenger systems. Conflicting findings regarding sensitivity of muscarinic signalling to cholesterol desorption, which perturbs lipid rafts and caveolae, have been reported, and no study has used human urinary bladder. Here, the dependence of human bladder muscarinic receptor signalling on plasma membrane cholesterol was examined. Nerve-mediated contraction, elicited by electrical field stimulation of human bladder strips, was impaired by desorption of cholesterol using methyl-beta-cyclodextrin, and the concentration-response curve for the muscarinic agonist carbachol was right-shifted. No effect of cholesterol desorption was observed in rat, and in mouse increased maximum contraction was seen. Expression of caveolin-1, PLCbeta1 and M3 muscarinic receptors did not differ between species in a manner that would explain the differential sensitivity to cholesterol desorption. In human bladder, threshold depolarisation eliminated the difference between cyclodextrin-treated and control preparations. Contraction elicited by depolarisation per se was not affected. M3 muscarinic receptors appeared clustered along plasma membrane profiles as shown by immunohistochemical staining of human bladder, but no redistribution in association with cholesterol reduction was seen. Thus, muscarinic receptor-induced contraction of the urinary bladder exhibits species-specific differences in its sensitivity to cholesterol desorption suggesting differential roles of lipid rafts/caveolae in muscarinic receptor signalling between species.

Muscarinic Receptor Binding and Plasma Drug Concentration after the Oral Administration of Propiverine in Mice

OBJECTIVES

The current study was undertaken to characterize the binding of propiverine to muscarinic receptors in mouse tissues by measuring plasma concentrations of the drug and its metabolite.

METHODS

At 0.5-24 h after the oral administration of propiverine at pharmacologically relevant doses, muscarinic receptors in tissue homogenates were measured by a radioligand binding assay using [N-methyl- (3) H]scopolamine (NMS), along with the drug's concentration in plasma by the liquid chromatography-tandem mass spectrometric method.

RESULTS

In the in vitro experiments, propiverine and its metabolite 1-methy-4-piperidyl benzilate N-oxide competed with [(3) H]NMS for binding sites in the bladder, submaxillary gland and heart of mice in a concentration-dependent manner. After the oral administration of propiverine, dose- and time-dependent increases in the dissociation constant for specific [(3) H]NMS binding were observed in the bladder and other tissues of mice, indicating that orally administered propiverine and/or its metabolite undergo significant binding to muscarinic receptors in mouse tissues. A longer-lasting binding of muscarinic receptor was seen in the bladder than in the submaxillary gland at relatively low doses of propiverine. Furthermore, the decrease in maximal number of binding sites values for [(3) H]NMS binding was more remarkable in the bladder than submaxillary gland of propiverine treated mice. There was a dose-dependent rise in the plasma concentrations of propiverine and 1-methy-4-piperidyl benzilate N-oxide in mice after the oral administration of propiverine.

CONCLUSION

The oral administration of propiverine exerts a more prominent and longer-lasting effect in the bladder than in the submaxillary gland of mice. The N-oxide metabolite may contribute significantly to the blockade of muscarinic receptors caused by oral propiverine.

Urothelial effects of oral agents for overactive bladder

The cholinergic system of the bladder includes muscarinic receptors distributed to detrusor myocytes and structures within mucosa including bladder afferent (sensory) nerves. The receptors have been shown to be involved in afferent signaling from the bladder, but it has not been established to what extent effects on this mucosal signaling pathway contribute to the therapeutic efficacy of the clinically used antimuscarinics. Mucosa can be influenced by antimuscarinics via the bloodstream. However, some antimuscarinics and their active metabolites are excreted in urine in amounts that may affect the mucosal muscarinic receptors from the luminal side. This has not yet been demonstrated to imply superior clinical efficacy. Nevertheless, mucosal afferent signaling pathways are therapeutically interesting targets that should be further explored.

Catecholamines relax detrusor through beta 2-adrenoceptors in mouse and beta 3-adrenoceptors in man

(-)-Isoproterenol [4-[1-hydroxy-2-[(1-methylethyl)amino]ethyl]-1,2-benzene diol hydrochloride] relaxes murine detrusor through beta-adrenoceptors (ARs); however, the beta-AR subtypes involved are unknown. beta(2)-ARs have been associated with caveolae, plasma-lemmal scaffolding domains that are absent in caveolin-1 (cav-1) knockout (KO) mice. Here, we studied detrusor responses in the absence and presence of beta-AR subtype-selective antagonists in wild-type (WT) and cav-1 KO mice. To inquire whether the murine detrusor model is relevant to man, beta-AR subtypes that mediate (-)-isoproterenol-evoked human detrusor relaxation were investigated. In WT mice, (-)-isoproterenol concentration-dependently relaxed the KCl (40 mM)-precontracted detrusor (-logEC(50)M = 8.04, E(max) = 62%). The effects of (-)-isoproterenol were surmountably antagonized by the beta(2)-AR-selective antagonist ICI 118,551 [(+/-)-1-[2,3-(dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol] (pK(B) = 9.28) but not affected by the beta(1)-AR-selective antagonist CGP 20712 [1-[2-((3-carbamoyl-4-hydroxy)phenoxy)ethylamino]-3-[4-(1-methyl-4-trifluoromethyl-2-imidazolyl)phenoxy]-2-propanol] and beta(3)-AR-selective L-748,337 [(S)-M-[4-[2-[3-[3-[acetamidomethyl)phenoxy)-2-hydroxypropyl]-amino]-ethyl]-phenylbenzsulfonamide)], suggesting involvement of beta(2)-AR only. The cav-1 KO detrusor displayed significant contractile dysfunction. (-)-Isoproterenol was less potent and efficient in relaxing detrusor from cav-1 KO (-logEC(50)M, 7.76; E(max) = 44%), but ICI 118,551 caused similar antagonism (pK(B) = 9.15), suggesting that beta(2)-AR function persisted in cav-1 KO. The beta(3)-AR-selective antagonist L-748,337 in the presence of ICI 118,551 and CGP 20712 caused additional blockade of (-)-isoproterenol effects in cav-1 KO, consistent with a beta(3)-AR involvement during relaxation and suppression of this effect in WT. (-)-Isoproterenol relaxed human detrusor muscle precontracted with carbachol (-logEC(50)M = 6.39, E(max) = 52%). However, the effects of (-)-isoproterenol in human detrusor were not blocked by CGP 20712 or ICI 118,551 but antagonized by L-748,337 (pK(B) = 7.65). We conclude that murine detrusor relaxation occurs via beta(2)-AR, and loss of caveolae does not perturb beta(2)-AR function but unmasks an additional activation of beta(3)-AR. In contrast, detrusor relaxation in man is mediated exclusively via beta(3)-AR.

Propiverine-induced accumulation of nuclear and cytosolic protein in F344 rat kidneys: isolation and identification of the accumulating protein

Male and female F344 rats but not B6C3F1 mice exposed for 104 weeks to propiverine hydrochloride (1-methylpiperid-4-yl 2,2-diphenyl-2-(1-propoxy)acetate hydrochloride), used for treatment of patients with neurogenic detrusor overactivity (NDO) and overactive bladder (OAB), presented with an accumulation of proteins in the cytosol and nuclei of renal proximal tubule epithelial cells, yet despite this, no increased renal tumor incidence was observed. In order to provide an improved interpretation of these findings and a better basis for human health risk assessment, male and female F344 rats were exposed for 16 weeks to 1000 ppm propiverine in the diet, the accumulating protein was isolated from the kidneys via cytosolic and nuclear preparations or laser-capture microdissection and analyzed using molecular weight determination and mass spectrometry. The accumulating protein was found to be d-amino acid oxidase (DAAO), an enzyme involved in amino and fatty acid metabolism. Subsequent reanalysis of kidney homogenate and nuclear samples as well as tissue sections using western blot and DAAO-immunohistochemistry, confirmed the presence and localization of DAAO in propiverine-treated male and female F344 rats. The accumulation of DAAO only in rats, and the limited similarity of rat DAAO with other species, including humans, suggests a rat-specific mechanism underlying the drug-induced renal DAAO accumulation with little relevance for patients chronically treated with propiverine.

Effects of three metabolites of propiverine on voltage-dependent L-type calcium currents in human atrial myocytes

The non-selective muscarinic receptor antagonist propiverine impairs L-type Ca(2+) currents (I(Ca,L)) in human detrusor smooth muscle cells and atrial cardiomyocytes. Here, we have investigated the effects of three metabolites of propiverine on human cardiac I(Ca,L). Propiverine reduced I(Ca)(,L) with a -logIC(50) [M] value of 4.1, M-5 only showed minor effect on I(Ca)(,L) at high concentrations, M-6 did not influence I(Ca)(,L) at all. Like the parent compound M-14 also reduced I(Ca)(,L) (-logIC(50) [M]=4.6). We conclude, that propiverine and M-14 reduce cardiac I(Ca)(,L) at higher concentrations than in detrusor cells and therefore preferentially reduce I(Ca)(,L) in the urinary bladder than in the heart.

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.

Actions of two main metabolites of propiverine (M-1 and M-2) on voltage-dependent L-type Ca2+ currents and Ca2+ transients in murine urinary bladder myocytes

The anticholinergic propiverine (1-methyl-4-piperidyl diphenylpropoxyacetate), which is used for the treatment of overactive bladder syndrome, has functionally active metabolites [M-1 (1-methyl-4-piperidyl diphenylpropoxyacetate N-oxide) and M-2 (1-methyl-4-piperidyl benzilate N-oxide)], but the site of actions of these metabolites is uncertain. Propiverine is rapidly absorbed after oral administration and is extensively biotransformed in the liver, giving rise to several active metabolites (M-1 and M-2). This study determines the effect of M-1 and M-2 on voltage-dependent nifedipine-sensitive inward Ca(2+) currents (I(Ca)) using patch-clamp techniques and fluorescent Ca(2+) imaging [after electrical field stimulation (EFS) and acetylcholine (ACh)] in the murine urinary bladder. In conventional whole-cell recording, propiverine and M-1 but not M-2 inhibited the peak amplitude of I(Ca) in a concentration-dependent manner at a holding potential of -60 mV (propiverine, K(i) = 10 microM; M-1, K(i) = 118 microM). M-1 shifted the steady-state inactivation curve of I(Ca) to the left at -90 mV by 7 mV. Carbachol (CCh) reversibly inhibited I(Ca). This inhibition probably occurred through muscarinic type 3 receptors, coupling with G-proteins, because nanomolar concentrations of 4-diphenylacetoxy-N-methyl-piperidine greatly reduced this inhibition, whereas pirenzepine or 11-([2-[(diethylamino)methyl]-1-piperdinyl]acetyl)-5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepine-6-one (AF-DX 116) at concentrations up to 1 microM was almost ineffective. In the presence of M-2, the CCh-induced inhibition of I(Ca) was blocked. In fluorescent Ca(2+) imaging, M-2 inhibited EFS-induced and ACh-induced Ca(2+) transients. These results suggest that M-1 acts, at least in part, as a Ca(2+) channel antagonist (as it inhibited I(Ca)), whereas M-2 has more direct antimuscarinic actions.

Electrophysiological profile of propiverine--relationship to cardiac risk

Drugs that prolong the QT interval by blocking human ether-a-go-go (HERG) channels may enhance the risk of ventricular arrhythmia. The spasmolytic drug propiverine is widely used for the therapy of overactive bladder (OAB). Here, we have investigated the effects of propiverine on cardiac ion channels and action potentials as well as on contractile properties of cardiac tissue, in order to estimate its cardiac safety profile, because other drugs used in this indication had to be withdrawn due to safety reasons. Whole-cell patch clamp technique was used to record the following cardiac ion currents: rapidly and slowly activating delayed rectifier K+ current (I(Kr), I(Ks)), ultra rapidly activating delayed rectifier K+ current (I(Kur)), inwardly rectifying K+ current I(K1), transient outward K+ current (I(to)), and L-type Ca2+ current (I(Ca,L)). Action potentials in cardiac tissue biopsies were recorded with conventional microelectrodes. The torsade de pointes screening assay (TDPScreen) was used for drug scoring. Propiverine blocked in a concentration-dependent manner HERG channels expressed in HEK293 cells, as well as native I(Kr) current in ventricular myocytes of guinea pig (IC50 values: 10 microM and 1.8 microM respectively). At high concentrations (100 microM), propiverine suppressed I(Ks). I(K1) and the transient outward current I(to) and I(Kur) were not affected. In guinea-pig ventricular and human atrial myocytes, propiverine also blocked I(Ca,L) (IC50 values: 34.7 microM and 41.7 microM, respectively) and reduced force of contraction. Despite block of I(Kr), action potential duration was not prolonged in guinea-pig and human ventricular tissue, but decreased progressively until excitation failed altogether. Similar effects were observed in dog Purkinje fibers. Propiverine obtained a low score in the TDPScreen. In conclusion, in vitro and in vivo studies of propiverine do not provide evidence for an enhanced cardiovascular safety risk. We propose that lack of torsadogenic risk of propiverine is related to enhancement of repolarization reserve by block of I(Ca,L).

Antimuscarinic Drug Inhibits Detrusor Overactivity Induced by Topical Application of Prostaglandin E 2 to the Urethra With a Decrease in Urethral Pressure

PURPOSE

Antimuscarinic drugs increase bladder capacity without prominent side effects such as urinary retention even when administered to patients with mild to moderate bladder outlet obstruction. Some mechanisms might exist in the urethra to compensate for the emptying function of the detrusor after the administration of antimuscarinic drugs. We investigated the influence of the antimuscarinic drug propiverine (Taiho Pharmaceutical, Tokyo, Japan) on urethral function.

MATERIALS AND METHODS

Urethral pressure and rhythmic bladder pressure were simultaneously monitored in urethane anesthetized female Sprague-Dawley rats. Prostaglandin E(2) was continuously administered intravesically or intraurethrally to induce detrusor overactivity. To eliminate the influence of bladder activity and monitor urethral baseline pressure isovolumetric pressure of the urethra was then recorded after cystectomy and ligation of the external urethral meatus. Furthermore, in vitro contractile responses of the urethral circular smooth muscle to field stimulation were examined in the presence of propiverine, tamsulosin (Taiho Pharmaceutical), verapamil, omega-conotoxin and atropine (Sigma).

RESULTS

Intravesical or intraurethral administration of prostaglandin E(2) significantly decreased the bladder contraction interval by 10.7% and 36.0%, respectively. Intra-arterial administration of 2 x 10(2) nM/kg propiverine significantly increased the bladder contraction interval in rats receiving intraurethral prostaglandin E(2) by 81.8% but it had no marked effect on rats receiving intravesical prostaglandin E(2). Significant decreases in urethral baseline pressure were found after propiverine administration. Field stimulation induced contraction was inhibited by propiverine and verapamil but not by tamsulosin, omega-conotoxin or atropine.

CONCLUSIONS

These results suggest that the inhibitory effects of propiverine are more prominent in rats with detrusor overactivity induced by intraurethral prostaglandin E(2) than by intravesical prostaglandin E(2). Propiverine may compensate for detrusor function by decreasing urethral resistance in the voiding phase.

Randomized, double-blind, placebo- and propiverine-controlled trial of the once-daily antimuscarinic agent solifenacin in Japanese patients with overactive bladder

OBJECTIVES

To compare solifenacin succinate (5 and 10 mg once-daily) to placebo and propiverine hydrochloride (20 mg once-daily), respectively, in Japanese patients with overactive bladder syndrome (OAB).

PATIENTS AND METHODS

A multicentre, 12-week, double-blind phase III trial randomized men and women aged > or = 20 years with OAB to solifenacin 5 or 10 mg, propiverine 20 mg, or placebo. Changes at endpoint in number of voids/24 h, urgency, incontinence, urgency incontinence and nocturia episodes, volume voided/void, restoration of continence and quality of life (QoL) were examined.

RESULTS

Of 1593 patients randomized, 1584 were treated; at the endpoint there were greater reductions in mean (sd) voids/24 h with solifenacin 5 mg, at -1.93 (1.97), and 10 mg, at -2.19 (2.09), and propiverine 20 mg, at -1.87 (2.70), than with placebo, at -0.94 (2.29) (P < 0.001 for all). Solifenacin (5 and 10 mg) was superior to placebo, and no worse than propiverine 20 mg, for this variable. There were significantly fewer mean (sd) urgency, incontinence and urgency incontinence episodes with solifenacin and propiverine than with placebo, with respective changes on placebo of - 1.28 (2.90), - 0.72 (1.95) and - 0.69 (2.00); solifenacin 5 mg, - 2.41 (2.88), -1.59 (2.12) and -1.45 (1.89) (P < 0.001 for all), and 10 mg, -2.78 (2.82), - 1.60 (1.81) and - 1.52 (1.77) (P < 0.001 for all), and propiverine 20 mg, -2.30 (3.08), -1.25 (2.79) and - 1.19 (2.20) (P < 0.001, = 0.002 and = 0.002 respectively). All active treatments vs placebo improved the volume voided (P < 0.001 for all) and QoL; solifenacin 10 mg reduced nocturia episodes (P = 0.021) and significantly improved urgency episodes (P = 0.012) and volume voided (P = 0.009) vs propiverine 20 mg, and solifenacin 5 mg caused less dry mouth (P = 0.003). Solifenacin 10 mg caused more dry mouth (P = 0.012) and occurrences of constipation (P = 0.004) than propiverine 20 mg, but discontinuation rates between both treatment groups were similar. Continence was restored at endpoint in more than half of the patients on active treatment.

CONCLUSION

Solifenacin 5 and 10 mg once daily significantly improved the symptoms of OAB compared with placebo. Solifenacin therapy at 5 mg once daily is well-tolerated; 10 mg can be given if additional efficacy is required.

Binding activities by propiverine and its N-oxide metabolites of L-type calcium channel antagonist receptors in the rat bladder and brain

The present study was undertaken to characterize the binding activities of propiverine and its N-oxide metabolites (1-methyl-4-piperidyl diphenylpropoxyacetate N-oxide: P-4(N-->O), 1-methyl-4-piperidyl benzilate N-oxide: DPr-P-4(N-->O)) toward L-type calcium channel antagonist receptors in the rat bladder and brain. Propiverine and P-4(N-->O) inhibited specific (+)-[(3)H]PN 200-110 binding in the rat bladder in a concentration-dependent manner. Compared with that for propiverine, the K(i) value for P-4(N-->O) in the bladder was significantly greater. Scatchard analysis has revealed that propiverine increased significantly K(d) values for bladder (+)-[(3)H]PN 200-110 binding. DPr-P-4(N-->O) had little inhibitory effects on the bladder (+)-[(3)H]PN 200-110 binding. Oxybutynin and N-desethyl-oxybutynin (DEOB) also inhibited specific (+)-[(3)H]PN 200-110 binding in the rat bladder. Propiverine, oxybutynin and their metabolites inhibited specific [N-methyl-(3)H]scopolamine methyl chloride ([(3)H]NMS) binding in the rat bladder. The ratios of K(i) values for (+)-[(3)H]PN 200-110 to [(3)H]NMS were markedly smaller for propiverine and P-4(N-->O) than oxybutynin and DEOB. Propiverine and P-4(N-->O) inhibited specific binding of (+)-[(3)H]PN 200-110, [(3)H]diltiazem and [(3)H]verapamil in the rat cerebral cortex in a concentration-dependent manner. The K(i) values of propiverine and P-4(N-->O) for [(3)H]diltiazem were significantly smaller than those for (+)-[(3)H]PN 200-110 and [(3)H]verapamil. Further, their K(i) values for [(3)H]verapamil were significantly smaller than those for (+)-[(3)H]PN 200-110. The K(i) values of propiverine for each radioligand in the cerebral cortex were significantly (P<0.05) smaller than those of P-4(N-->O). In conclusion, the present study has shown that propiverine and P-4(N-->O) exert a significant binding activity of L-type calcium channel antagonist receptors in the bladder and these effects may be pharmacologically relevant in the treatment of overactive bladder after oral administration of propiverine.

Contribution of Ca2+ influx to carbachol-induced detrusor contraction is different in human urinary bladder compared to pig and mouse

Carbachol-induced detrusor contractions are mainly mediated via M3 receptor subtype and depend not only on Ca2+ release from the intracellular calcium stores but also on Ca2+ influx via L-type Ca2+ channels. The purpose of this study was to examine the different contributions of Ca2+ influx and Ca2+ release underlying muscarinic receptor-mediated contractions in human, porcine and murine urinary bladder. Detrusor contractions were measured in urothelium-denuded detrusor strips as responses to cumulatively increasing carbachol concentrations, release of intracellular Ca2+ was determined in Chinese hamster ovary cells stably transfected with human muscarinic M3 (hM3) receptors. In human tissue, 1 microM of the L-type Ca2+-channel blocker nifedipine reduced carbachol contractions to 74%, in pig to 18% and in mouse to 27% of pre-drug controls. 2-aminoethoxyphenyl borate (2-APB, 300 microM), which impairs inositol trisphosphate (IP3)-induced release of Ca2+, reduced carbachol responses in human detrusor to 60%, in pig to 35% and in mouse to 20%, whereas block of the Ca2+-induced Ca2+ release with ryanodine had no significant effect on carbachol contractions in all three species. Carbachol-induced release of intracellular Ca2+ in Chinese hamster ovary cells expressing muscarinic hM3 receptors was completely prevented by 100 microM 2-APB. The direct intracellular IP3 receptor antagonist xestospongin C (10 microM) reduced carbachol-stimulated intracellular Ca2+ to 41% of the control value. Blockade of ATP-dependent Ca2+ uptake into intracellular stores with thapsigargin was associated with a concentration-dependent increase of detrusor contraction, but limited on-top contractions with carbachol. In conclusion, carbachol-induced contractions in human, porcine and mouse detrusor depend differently on Ca2+ influx, since potency of nifedipine reducing muscarinic receptor-mediated detrusor contraction is lower in human bladder. On the other hand, slight species differences are also found when inhibiting IP3-induced Ca2+ release and Ca2+ reuptake into intracellular stores. Taken together, our data show considerable species differences between human, porcine and murine detrusor regarding the relative contributions of Ca2+ influx and maybe also carbachol-induced Ca2+ release that could be of relevance when using different animal models.

A gap junction blocker inhibits isolated whole bladder activity in normal rats and rats with partial bladder outlet obstruction

We examined the effect of 18alpha-glycyrrhetinic acid (18alpha-GA), a gap junction blocker, or propiverine hydrochloride on the activity of isolated whole bladders obtained from intact rats and rats with partial bladder outlet obstruction (BOO). Thirty-two female Sprague-Dawley rats were divided into an intact group and a BOO group. The whole bladder was harvested from each rat and isovolumetric cystometry was performed in Krebs solution. Changes of bladder activity were recorded after addition of 18alpha-GA or propiverine hydrochloride to the perfusate. Propiverine hydrochloride inhibited the amplitude and duration of contraction in both intact and BOO groups. Propiverine hydrochloride also reduced the baseline bladder pressure in the BOO group, but not in the intact group. In contrast, 18alpha-GA inhibited the amplitude and duration of bladder contraction, and also reduced the baseline pressure, in both intact and BOO groups. BOO bladders showed inhibition of the amplitude and duration of bladder contraction at lower concentrations of 18alpha-GA than intact bladders. A gap junction blocker suppressed the in vitro activity of BOO bladders more effectively than that of intact bladders. Therefore, inhibition of intercellular communication in the bladder via gap junctions may be useful for treating detrusor overactivity, as well as propiverine hydrochloride.

Propiverine Hydrochloride Immediate and Extended Release: Comparison of Efficacy and Tolerability in Patients with Overactive Bladder

INTRODUCTION

This study aims to compare the efficacy of propiverine hydrochloride immediate release (IR), propiverine hydrochloride extended release (ER) and placebo for the treatment of overactive bladder syndrome. The primary outcome measure is incontinence episode frequency, with secondary outcome measures including mean volume per void and quality of life as assessed on King's Health Questionnaire.

MATERIAL AND METHODS

The double-blind, double-dummy, randomized study compared IR 15 mg twice daily, ER 30 mg once daily and placebo in 3 parallel groups. After a run-in period of 7 days, the patients were treated for 32 days. Nine hundred and eighty-eight patients were randomized, and 910 patients completed the protocol without major violations.

RESULTS

The number of incontinence episodes/24 h decreased by 2.26 in the IR group (p < 0.001 vs. placebo), by 2.46 in the ER group (p < 0.0001 vs. placebo) and by 1.75 in the placebo group. The most frequent adverse event was dry mouth with 22.8% of the patients in the IR group, 21.7% in the ER group and 6.4% in the placebo group. The overall tolerability was rated 'very good' or 'good' by more than 80% of the investigators and patients in all 3 groups.

CONCLUSIONS

Propiverine ER 30 mg once daily and propiverine IR 15 mg twice daily significantly reduce the number of incontinence episodes/24 h within a treatment period of 32 days. Both formulations are safe and well tolerated. The extended release formulation of propiverine is a suitable new option for the treatment of the overactive bladder.

Propiverine and metabolites: differences in binding to muscarinic receptors and in functional models of detrusor contraction

Propiverine is a commonly used antimuscarinic drug used as therapy for symptoms of an overactive bladder. Propiverine is extensively biotransformed into several metabolites that could contribute to its spasmolytic action. In fact, three propiverine metabolites (M-5, M-6 and M-14) have been shown to affect various detrusor functions, including contractile responses and L-type calcium-currents, in humans, pigs and mice, albeit with different potency. The aim of our study was to provide experimental evidence for the relationship between the binding of propiverine and its metabolites to human muscarinic receptor subtypes (hM(1)-hM(5)) expressed in chinese hamster ovary cells, and to examine the effects of these compounds on muscarinic receptor-mediated detrusor function. Propiverine, M-5, M-6 and M-14 bound to hM(1)-hM(5) receptors with the same order of affinity for all five subtypes: M-6 > propiverine > M-14 > M-5. In HEK-293 cells expressing hM(3), carbachol-induced release of intracellular Ca(2+) ([Ca(2+)](i)) was suppressed by propiverine and its metabolites; the respective concentration-response curves for carbachol-induced Ca(2+)-responses were shifted to the right. At higher concentrations, propiverine and M-14, but not M-5 and M-6, directly elevated [Ca(2+)](i). These results were confirmed for propiverine in human detrusor smooth muscle cells (hDSMC). Propiverine and the three metabolites decreased detrusor contractions evoked by electric field stimulation in a concentration-dependent manner, the order of potency being the same as the order of binding affinity. We conclude that, in comparison with the parent compound, loss of the aliphatic side chain in propiverine metabolites is associated with higher binding affinity to hM(1)-hM(5) receptors and higher functional potency. Change from a tertiary to a secondary amine (M-14) results in lower binding affinity and reduced potency. Oxidation of the nitrogen (M-5) further lowers binding affinity as well as functional potency.

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 rilmakalim on detrusor contraction in the presence and absence of urothelium

Openers of K(ATP) channels are known to inhibit KCl-, carbachol- and also electrically induced contractions in detrusor muscle strips from various species. Contractions of isolated strips of urinary bladder are usually of higher amplitude when the urothelium has been removed. This has been explained by the release of an urothelium-derived relaxing factor. In this study we examined whether intact urothelium may modulate the effect of the selective KATP channel opener rilmakalim. Contractile responses to 85 mM KCl and 10 microM carbachol were measured in detrusor strips from mouse, pig and man. In the presence of an intact urothelium, contractions were significantly reduced in strips from all three species investigated. In preparations with urothelium rilmakalim reduced KCl contractions with similar potency and efficacy [-logIC50 (M) 4.6 to 5.1; Effmax reduction to 14-30% of control]. However, in urothelium-denuded strips rilmakalim was more potent in pig (-logIC50 5.5) than in mouse and man (-logIC50 4.7 and 4.4, respectively). The order of potency for rilmakalim to suppress carbachol-induced contractions was pig (-logIC50 6.7)>man (5.8)>mouse (4.7); contractions were significantly more reduced in pig (Effmax reduction to 11+/-2%, n=10) and in mouse (21+/-2%, n=8) than in human detrusor (55+/-5%, n=5). The presence of urothelium did not affect the concentration-response curves for rilmakalim, with the exception of KCl-induced contractions in pig. Only the rilmakalim-induced relaxation of carbachol-mediated contractions in pig were prevented by the KATP channel blocker glibenclamide. We conclude that with this one exception, the responses to rilmakalim in detrusor contractions were not mediated by KATP channel opening.

Juvenile pig detrusor: Effects of propiverine and three of its metabolites

In isolated detrusor strips, propiverine is known to be effective to decrease contractions elicited by electric field stimulation (EFS). Here we investigated whether the metabolites M-5, M-6 and M-14 of propiverine retain the pharmacological properties of the parent compound also in juvenile organisms. EFS-induced contractions of detrusor strips from juvenile pigs are more sensitive to atropine than strips from mature pigs. The atropine-resistant component of contraction is also significantly larger in juvenile pigs. Propiverine, its metabolites M-5, M-14 and also tolterodine completely reduced detrusor contraction in juvenile pigs. M-6 almost did not affect atropine-resistant contractions. We conclude that juvenile pig detrusors possess a higher atropine-resistant component of EFS-elicited contraction. Nevertheless order of potency and efficacy of propiverine and its metabolites M-5 and M-14 are similar in juvenile and mature pigs, while M-6 only reduces atropine-sensitive contractions in the juvenile organism.