Antimuscarinics and the overactive detrusor--which is the main mechanism of action?

Pathophysiology of Overactive Bladder and Pharmacologic Treatments Including β3-Adrenoceptor Agonists -Basic Research Perspectives

Overactive bladder (OAB) is a symptom-based syndrome defined by urinary urgency, frequency, and nocturia with or without urge incontinence. The causative pathology is diverse; including bladder outlet obstruction (BOO), bladder ischemia, aging, metabolic syndrome, psychological stress, affective disorder, urinary microbiome, localized and systemic inflammatory responses, etc. Several hypotheses have been suggested as mechanisms of OAB generation; among them, neurogenic, myogenic, and urothelial mechanisms are well-known hypotheses. Also, a series of local signals called autonomous myogenic contraction, micromotion, or afferent noises, which can occur during bladder filling, may be induced by the leak of acetylcholine (ACh) or urothelial release of adenosine triphosphate (ATP). They can be transmitted to the central nervous system through afferent fibers to trigger coordinated urgency-related detrusor contractions. Antimuscarinics, commonly known to induce smooth muscle relaxation by competitive blockage of muscarinic receptors in the parasympathetic postganglionic nerve, have a minimal effect on detrusor contraction within therapeutic doses. In fact, they have a predominant role in preventing signals in the afferent nerve transmission process. β3-adrenergic receptor (AR) agonists inhibit afferent signals by predominant inhibition of mechanosensitive Aδ-fibers in the normal bladder. However, in pathologic conditions such as spinal cord injury, it seems to inhibit capsaicin-sensitive C-fibers. Particularly, mirabegron, a β3-agonist, prevents ACh release in the BOO-induced detrusor overactivity model by parasympathetic prejunctional mechanisms. A recent study also revealed that vibegron may have 2 mechanisms of action: inhibition of ACh from cholinergic efferent nerves in the detrusor and afferent inhibition via urothelial β3-AR.

Intracellular signaling pathways of muscarinic acetylcholine receptor-mediated detrusor muscle contractions

Acetylcholine plays an essential role in the regulation of detrusor muscle contractions, and antimuscarinics are widely used in the management of overactive bladder syndrome. However, several adverse effects limit their application and patients' compliance. Thus, this study aimed to further analyze the signal transduction of M2 and M3 receptors in the murine urinary bladder to eventually find more specific therapeutic targets. Experiments were performed on adult male wild-type, M2, M3, M2/M3, or Gαq/11 knockout (KO), and pertussis toxin (PTX)-treated mice. Contraction force and RhoA activity were measured in the urinary bladder smooth muscle (UBSM). Our results indicate that carbamoylcholine (CCh)-induced contractions were associated with increased activity of RhoA and were reduced in the presence of the Rho-associated kinase (ROCK) inhibitor Y-27632 in UBSM. CCh-evoked contractile responses and RhoA activation were markedly reduced in detrusor strips lacking either M2 or M3 receptors and abolished in M2/M3 KO mice. Inhibition of Gαi-coupled signaling by PTX treatment shifted the concentration-response curve of CCh to the right and diminished RhoA activation. CCh-induced contractile responses were markedly decreased in Gαq/11 KO mice; however, RhoA activation was unaffected. In conclusion, cholinergic detrusor contraction and RhoA activation are mediated by both M2 and M3 receptors. Furthermore, whereas both Gαi and Gαq/11 proteins mediate UBSM contraction, the activation at the RhoA-ROCK pathway appears to be linked specifically to Gαi. These findings may aid the identification of more specific therapeutic targets for bladder dysfunctions.NEW & NOTEWORTHY Muscarinic acetylcholine receptors are of utmost importance in physiological regulation of micturition and also in the development of voiding disorders. We demonstrate that the RhoA-Rho-associated kinase (ROCK) pathway plays a crucial role in contractions induced by cholinergic stimulation in detrusor muscle. Activation of RhoA is mediated by both M2 and M3 receptors as well as by Gi but not Gq/11 proteins. The Gi-RhoA-ROCK pathway may provide a novel therapeutic target for overactive voiding disorders.

Meta-Analysis of the Efficacy and Safety of Imidafenacin for Overactive Bladder Induced by Benign Prostatic Hyperplasia in Men Receiving Alpha-Blocker Therapy

Purpose

The aim of this meta-analysis was to evaluate the efficacy and safety of imidafenacin for overactive bladder (OAB) induced by benign prostatic hyperplasia (BPH) in men receiving alpha-blocker monotherapy.

Methods

We performed a systematic research of the PubMed, Embase, and Cochrane Library databases, and searched for studies about alpha-blocker with or without imidafenacin treatment for OAB in patients with BPH. We also investigated the original references of the included texts.

Results

Four randomized controlled trials including 779 participants with BPH (389 in the alpha-blocker+imidafenacin group and 390 in the alpha-blocker only group) were studied. The main efficacy endpoint was the Overactive Bladder Symptom Score, which showed a mean difference of -1.88 (95% confidence interval, -2.32 to -1.44; P<0.00001), suggesting that alpha-blocker and imidafenacin treatment was effective in treating men with OAB. As other primary efficacy end points, the International Prostate Symptom Score (IPSS) total score (P=0.47), the IPSS storage symptom score (P=0.07), the IPSS voiding symptom score (P=0.60), and the IPSS quality of life score (P=0.18) indicated that 2 methods had no significant differences in treating men with OAB. In terms of safety, which was assessed using postvoid residual volume (P=0.05) and maximum flow rate (P=0.53), the analysis suggested that combination treatment was very well tolerated.

Conclusions

This study suggested that imidafenacin plus alpha-blocker was an efficacious and safe treatment for OAB symptoms in BPH patients.

Functional atropine sensitive purinergic responses in the healthy rat bladder

While acetylcholine is regarded to be the main directly contractile transmitter substance in the urinary bladder, interactions with other transmitters likely occur. Presently, the interplay between purinergic and cholinergic signalling was investigated to unravel the involvement of the urothelium and efferent neurons in the functionally important purinergically evoked release of acetylcholine in vitro. Functional characterization of receptor subtypes involved in this interplay was also performed. In vitro organ bath experiments with electrical field stimulation (EFS) or administration of agonist were performed in the absence and presence of the neurotoxin tetrodotoxin (TTX; 5 × 10^-7 M) and/or receptor antagonists, in intact and urothelium-denuded full thickness rat bladder strip preparations. Interestingly, functional contractions to ATP (10^-6-10^-3 M) remained unaffected by TTX, but were significantly lowered in the presence of the muscarinic antagonist atropine (10^-6 M). However, in urothelium-denuded strip preparations, this latter phenomenon was not present and the ATP response remained unaltered. To rule out purinergic interference caused by break-down of ATP, experiments were performed in which the stable ATP-analogue αβMeATP (10^-7-10^-5 M) gave rise to functional atropine-sensitive contractions. Furthermore, contractions to ATP were not affected by P2Y6 purinoceptor blockade (by MRS2578; 10^-7, 10^-5 M), nor were relaxatory responses to ATP sensitive to atropine, PPADS (3 × 10^-5 M) or αβMeATP. Lastly, relaxations to ADP (10^-6-10^-3 M) or NECA (10^-8-10^-5 M) were unaltered by the presence of atropine. To conclude, purinergic functional contractile, but not relaxatory, responses are supported by the cholinergic transmitter system in vitro, through non-neuronal mechanisms in the urothelium. Involved purinoceptors are of the P2X-subtype, most likely P2X1 and/or P2X3.

A Novel Alternative in the Treatment of Detrusor Overactivity? In Vivo Activity of O-1602, the Newly Synthesized Agonist of GPR55 and GPR18 Cannabinoid Receptors

The aim of the research was to assess the impact of O-1602—novel GPR55 and GPR18 agonist—in the rat model of detrusor overactivity (DO). Additionally, its effect on the level of specific biomarkers was examined. To stimulate DO, 0.75% retinyl acetate (RA) was administered to female rats’ bladders. O-1602, at a single dose of 0.25 mg/kg, was injected intra-arterially during conscious cystometry. Furthermore, heart rate, blood pressure, and urine production were monitored for 24 h, and the impact of O-1602 on the levels of specific biomarkers was evaluated. An exposure of the urothelium to RA changed cystometric parameters and enhanced the biomarker levels. O-1602 did not affect any of the examined cystometric parameters or levels of biomarkers in control rats. However, the O-1602 injection into animals with RA-induced DO ameliorated the symptoms of DO and caused a reversal in the described changes in the concentration of CGRP, OCT₃, BDNF, and NGF to the levels observed in the control, while the values of ERK1/2 and VAChT were significantly lowered compared with the RA-induced DO group, but were still statistically higher than in the control. O-1602 can improve DO, and may serve as a promising novel substance for the pharmacotherapy of bladder diseases.

Change of Detrusor Contractility in Patients with and without Bladder Outlet Obstruction at Ten or More Years of follow-up

To analyze the change of detrusor contractility by investigating urodynamic characteristics with long term follow-up. This study retrospectively reviewed 166 lower urinary tract symptoms patients without bladder outlet obstruction (BOO) and 63 patients with BOO who underwent repeated urodynamic studies at the first time and more than 10 years later. The urodynamic parameters, bladder contractility index (BCI), and BOO index (BOOI) were compared before and after. As time goes by, detrusor pressure at maximum flow rate (PdetQmax) significantly decreased and post-void residual (PVR) volume significantly increased in both men and women. Full sensation, urge sensation, voided volume, and BCI significantly decreased. We also compared men with and without BOO, PdetQmax, maximum flow rate (Qmax), voided volume, and BCI all significantly decreased in both groups without difference. PVR increased greater in men with BOO after >10 years significantly (p = 0.036). Women with detrusor overactivity (DO) under antimuscarinic showed no significant BCI change compared to patients without DO (p = 0.228). Detrusor contractility decreases in men and women after >10 years of follow-up. However, this finding suggests that patients with BOO or DO under adequate medical treatment, detrusor contractility is not aggravated over 10 or more years of follow-up.

The mechanical stop test and isovolumetric detrusor contractile reserve are associated with immediate spontaneous voiding after transurethral resection of prostate

PURPOSE

To identify urodynamic factors associated with the mechanical stop test and immediate spontaneous voiding following transurethral resection of prostate (TURP).

METHODS

We identified 90 men who underwent TURP over a 12-month period. Forty-three (mean age 68 years) underwent urodynamic evaluation prior to TURP. Isovolumetric detrusor contractile pressure (P_iso) was obtained using the mechanical stop test during the voiding phase, and used to calculate detrusor contractile reserve (P_res = P_iso - P_det@Q_max). Primary outcome was spontaneous voiding after TURP.

RESULTS

Preoperative catheter-free spontaneous voiding was present in 63% of men (27/43) with a urodynamic (mean ± SD): Q_max 6.2 ± 2.7 mL/s, P_det@Q_max 102 ± 47 cmH₂O, P_iso 124 ± 49 cmH₂O, P_res 22 ± 16 cmH₂O, bladder outlet obstruction index (BOOI) 90 ± 49, and bladder contractility index (BCI) 132 ± 44. The remaining 16 catheter-dependent men demonstrated a urodynamic (mean ± SD): Q_max 3.6 ± 3.3 mL/s, P_det@Q_max 87 ± 38 cmH₂O, P_iso 99 ± 51 cmH₂O, P_res 10 ± 18 cmH₂O, BOOI 82 ± 36, and BCI 106 ± 48. Following TURP, 67% of men voided spontaneously with their first void trial, and in receiver operator analysis of urodynamic measures (P_det@Q_max, P_iso, P_res, BOOI and BCI), only P_res was significantly associated with immediate spontaneous voiding after TURP (threshold P_res ≥ 9 cmH₂O, AUC = 0.681, p = 0.035).

CONCLUSIONS

In men who underwent TURP, a P_res ≥ 9 cmH₂O was associated with immediate spontaneous voiding and may be easily incorporated into the postoperative pathway.

Expression of components of the urothelial cholinergic system in bladder and cultivated primary urothelial cells of the pig

BACKGROUND

Porcine urinary bladders are widely used for uro-pharmacological examinations due to their resemblance to the human organ. However, characterisations of the porcine urothelium at the molecular level are scarce up to now. As it has become clear over the last years that this tissue plays an important role in the signaling-pathways of the bladder, we examined whether the transporter and receptor pattern (with focus on the transmitter acetylcholine) is comparable to the human urothelium. With regard to in vitro studies, we also investigated if there is a difference between the native tissue and cultivated primary urothelial cells in culture.

METHODS

Urothelium from German Landrace and Göttingen Minipig bladders was collected. One part of the German Landrace tissue was used for cultivation, and different passages of the urothelial cells were collected. The actual mRNA expression of different transporters and receptors was examined via quantitative real-time PCR. These included the vesicular acetylcholine transporter (VAChT), the choline acetyl transferase (ChAT), organic cation transporters 1-3 (OCT1-3), organic anion transporting polypeptide 1A2 (OATP1A2), P-glycoprotein (ABCB1), the carnitine acetyl-transferase (CarAT), as well as the muscarinic receptors 1-5 (M1-5).

RESULTS

There is a strong qualitative resemblance between the human and the porcine urothelium with regard to the investigated cholinergic receptors, enzymes and transporters. CarAT, OCT1-3, OATP1A2 and ABCB1 could be detected in the urothelium of both pig races. Moreover, all 5 M-receptors were prominent with an emphasis on M2 and M3. VAChT and ChAT could not be detected at all. Cultures of the derived urothelial cells showed decreased expression of all targets apart from ABCB1 and CarAT.

CONCLUSIONS

Based on the expression pattern of receptors, transporters and enzymes of the cholinergic system, the porcine urinary bladder can be regarded as a good model for pharmacological studies. However, cultivation of primary urothelial cells resulted in a significant drop in mRNA expression of the targets. Therefore, it can be concluded that the intact porcine urothelium, or the whole pig bladder, may be appropriate models for studies with anticholinergic drugs, whereas cultivated urothelial cells have some limitation due to significant changes in the expression levels of relevant targets.

Anti-muscarinic drugs increase rectal compliance and exacerbate constipation in chronic spinal cord injury : Anti-muscarinic drug effect on neurogenic bowel

STUDY DESIGN

Prospective cohort study OBJECTIVES: We hypothesized that anti-muscarinic agents alter rectal compliance in SCI patients and that altered rectal compliance relates to bowel symptomatology. Our primary aim was to compare rectal compliance before and after the institution of anti-muscarinics (solifenacin and tolterodine) and an adrenoceptor agonist (mirabegron) in these patients. Additionally, we wanted to evaluate if anorectal manometry differed before and after use of anti-muscarinic agents.

SETTING

Tertiary neurogastroenterology clinic, London METHODS: Thirty-five patients with supraconal spinal cord injury (SCI) underwent anal manometry, assessment of rectoanal inhibitory reflex (RAIR) and rectal compliance before and after anti-muscarinic treatment (for overactive bladder) was started (mean follow-up 12 weeks). Patients were assessed identically, pre-and post-treatment (solifenacin n = 17, tolterodine n = 10, mirabegron n = 8). Doses used were as for non-SCI patients.

RESULTS

Resting, squeeze and cough pressures were unchanged after anti-muscarinic treatment. Rectal compliance was significantly raised after anti-muscarinic treatment (p = 0.001). The percent amplitude of maximal sphincter relaxation of the RAIR was decreased (p < 0.001) and excitation latency was increased (p = 0.006). There was no significant change in the duration of recovery of the RAIR. There was a significant increase of the Wexner Constipation Score (p = 0.001) but no change in the Wexner Incontinence Score. There was a significant correlation between change in rectal compliance and change in Wexner Constipation Score (p = 0.001). Thus, increasing compliance of the rectum is associated with worsening of constipation after anti-muscarinic therapy. However, there were no changes in anorectal manometry or rectal compliance in those who received mirabegron.

CONCLUSION

Anti-muscarinic therapy for overactive bladder increases compliance of the neurogenic rectum and alters anorectal reflex activity, with worsening of constipation.

Singapore Urological Association Clinical Guidelines for Male Lower Urinary Tract Symptoms/Benign Prostatic Hyperplasia

The first clinical guidelines for male lower urinary tract symptoms (LUTS)/benign prostatic hyperplasia (BPH) were published in 2005. An update is urgently needed in view of BPH being recognised as one of ten chronic illnesses by the Ministry of Health, Singapore. This review summarises the definition of BPH and the epidemiology of male LUTS/BPH in Singapore. BPH can be phenotyped with noninvasive transabdominal ultrasonography, according to intravesical prostatic protrusion and prostate volume, and classified according to severity (staging) for individualised treatment. At the initial evaluation, the majority of patients (59%) can be managed with fluid adjustment, exercise and diet; 32% with medications, using alpha blockers and/or 5-alpha reductase inhibitors for prostates weighing more than 30 g; and 9% with surgical intervention for more advanced disease. The 2015 guidelines comprise updated evidence that will help family medicine practitioners and specialists manage this common ailment more cost-effectively.

Altered detrusor contractility in MPTP-treated common marmosets with bladder hyperreflexia

Bladder hyperreflexia is a common non-motor feature of Parkinson's disease. We now report on the contractility of the isolated primate detrusor strips devoid of nerve input and show that following MPTP, the amplitude and frequency of spontaneous contraction was increased. These responses were unaffected by dopamine D1 and D2 receptor agonists A77636 and ropinirole respectively. Contractions by exogenous carbachol, histamine or ATP were similar and no differences in the magnitude of noradrenaline-induced relaxation were seen in detrusor strip obtained from normal and MPTP-treated common marmosets (Callithrix jacchus). However, the neurogenic contractions following electrical field stimulation of the intrinsic nerves (EFS) were markedly greater in strips obtained from MPTP treated animals. EFS evoked non-cholinergic contractions following atropine were also greater but the contribution of the cholinergic innervation as a proportion of the overall contraction was smaller in the detrusor strips of MPTP treated animals, suggesting a preferential enhancement of the non-cholinergic transmission. Although dopaminergic mechanism has been proposed to underlie bladder hyperreflexia in MPTP-treated animals with intact bladder, the present data indicates that the increased neurogenically mediated contractions where no extrinsic innervation exists might be due to long-term adaptive changes locally as a result of the loss of the nigrostriatal output.

Cardiovascular safety in refractory incontinent patients with overactive bladder receiving add-on mirabegron therapy to solifenacin (BESIDE)

AIMS/OBJECTIVES

In the BESIDE study, combination therapy (antimuscarinic [solifenacin] and β₃ -adrenoceptor agonist [mirabegron]) improved efficacy over solifenacin monotherapy without exacerbating anticholinergic side effects in overactive bladder (OAB) patients; however, a potential synergistic effect on the cardiovascular (CV) system requires investigation.

METHODS

OAB patients remaining incontinent despite daily solifenacin 5 mg during 4-week single-blind run-in, were randomised 1:1:1 to double-blind daily combination (solifenacin 5 mg/mirabegron 25 mg, increasing to 50 mg after week 4), solifenacin 5 or 10 mg for 12 weeks. CV safety assessments included frequency of CV-related treatment-emergent adverse events (TEAEs), change from baseline in vital signs (systolic blood pressure [SBP], diastolic blood pressure [DBP], pulse rate) and electrocardiogram (ECG) parameters.

RESULTS

The frequency of hypertension, tachycardia and ECG QT prolongation, respectively, was low and comparable across combination (1.1%, 0.3%, 0.1%), solifenacin 5 mg (0.7%, 0.1%, 0.1%), and solifenacin 10 mg groups (0.8%, 0%, 0.1%). Adjusted mean (SE) change from baseline to end of treatment (EoT) in SBP, DBP, and pulse rate with combination (0.07 mm Hg [0.38], -0.35 mm Hg [0.26], 0.47 bpm [0.28]), solifenacin 5 mg (-0.93 mm Hg [0.38], -0.45 mm Hg [0.26], 0.43 bpm [0.28]) and solifenacin 10 mg (-1.28 mm Hg [0.38], -0.48 mm Hg [0.26], 0.27 bpm [0.28]) was generally comparable, with the exception of a mean treatment difference of ~1 mm Hg in SBP between combination and solifenacin monotherapy; SBP was unchanged with combination and decreased with solifenacin monotherapy. Mean changes from baseline to EoT in ECG parameters were generally similar across treatment groups, except for QT interval corrected using Fridericia's formula, which was higher with solifenacin 10 mg (3.30 mseconds) vs. combination (0.49 mseconds) and solifenacin 5 mg (0.77 mseconds).

CONCLUSION

The comparable frequency of CV-related TEAEs, changes in vital signs and ECG parameters indicates no synergistic effect on CV safety outcomes when mirabegron and solifenacin are combined.

A multicenter real-life study of the efficacy of an alpha-blocker with or without anticholinergic agent (imidafenacin) treatment in patients with lower urinary tract symptoms/benign prostatic hyperplasia and storage symptoms

AIMS

To evaluate the efficacy and safety of combination therapy comprising a short-acting anticholinergic, imidafenacin and an alpha-blocker compared with monotherapy with an alpha-blocker only in men with lower urinary tract symptoms (LUTS) and storage symptoms.

METHODS

The 12-week, prospective, double-blind, randomised trial enrolled men with LUTS and storage symptom. The inclusion criteria were a total International Prostate Symptom Score (IPSS) ≥12, an IPSS question 4 score ≥2, ≥8 micturitions in 24 hours, and a prostate volume >20 mL. The primary outcome was a change in the micturition number from baseline. Bladder diary variables, Patient Perception of Intensity of Urgency Scale (PPIUS) scores, IPSS and safety were assessed.

RESULTS

Of 260 patients screened, 221 completed the study. Patients were randomly assigned to receive an alpha-blocker only (n=111, group 1) or combination therapy comprising an alpha-blocker and an anticholinergic (n=110, group 2) for 12 weeks. Group 1 and 2 showed significant improvement in their 24-hour micturition numbers (-1.87 and -2.08, respectively), nocturia episodes (-0.48 and -0.53, respectively), total IPSS (-9.9 and -8.8, respectively), and PPIUS scores (-0.19 and -0.24, respectively). Micturition number per 24 hours, daytime frequency, urgency, the PPIUS score, the IPSS question 4 score and IPSS QoL score improved significantly in the combination therapy group, but changes in total IPSS, nocturia episodes, and safety outcomes did not differ significantly between the groups.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Compared with treatment with an alpha-blocker alone, combination therapy comprising an anticholinergic and an alpha-blocker showed superior efficacy and its safety was similar in patients with LUTS and storage symptoms.

Acetylcholinesterase Inhibitors and Drugs Acting on Muscarinic Receptors- Potential Crosstalk of Cholinergic Mechanisms During Pharmacological Treatment

BACKGROUND

Pharmaceuticals with targets in the cholinergic transmission have been used for decades and are still fundamental treatments in many diseases and conditions today. Both the transmission and the effects of the somatomotoric and the parasympathetic nervous systems may be targeted by such treatments. Irrespective of the knowledge that the effects of neuronal signalling in the nervous systems may include a number of different receptor subtypes of both the nicotinic and the muscarinic receptors, this complexity is generally overlooked when assessing the mechanisms of action of pharmaceuticals.

METHODS

We have search of bibliographic databases for peer-reviewed research literature focused on the cholinergic system. Also, we have taken advantage of our expertise in this field to deduce the conclusions of this study.

RESULTS

Presently, the life cycle of acetylcholine, muscarinic receptors and their effects are reviewed in the major organ systems of the body. Neuronal and non-neuronal sources of acetylcholine are elucidated. Examples of pharmaceuticals, in particular cholinesterase inhibitors, affecting these systems are discussed. The review focuses on salivary glands, the respiratory tract and the lower urinary tract, since the complexity of the interplay of different muscarinic receptor subtypes is of significance for physiological, pharmacological and toxicological effects in these organs.

CONCLUSION

Most pharmaceuticals targeting muscarinic receptors are employed at such large doses that no selectivity can be expected. However, some differences in the adverse effect profile of muscarinic antagonists may still be explained by the variation of expression of muscarinic receptor subtypes in different organs. However, a complex pattern of interactions between muscarinic receptor subtypes occurs and needs to be considered when searching for selective pharmaceuticals. In the development of new entities for the treatment of for instance pesticide intoxication, the muscarinic receptor selectivity needs to be considered. Reactivators generally have a muscarinic M2 receptor acting profile. Such a blockade may engrave the situation since it may enlarge the effect of the muscarinic M3 receptor effect. This may explain why respiratory arrest is the major cause for deaths by esterase blocking.

Expressions of urothelial functional proteins in idiopathic detrusor overactivity patients refractory to antimuscarinic therapy with different urodynamic characteristics

AIMS

This study investigated the expressions of PGP9.5, P₂  X ₃ , muscarinic receptor (M3) and beta-3 adrenoreceptor (AR) in idiopathic detrusor overactivity (IDO) patients refractory to antimuscarinic treatment, and analyzed the correlation between protein expressions and clinical symptoms of IDO bladders with different urodynamic characteristics.

METHODS

Specimens of 48 IDO and 10 control patients without lower urinary tract symptoms were included. The levels of these proteins from bladder mucosa were determined by Western blotting.

RESULTS

The expression levels of β3-AR and M3 receptor were similar between IDO patients and controls. When IDO patients were divided into two subgroups, phasic DO and terminal DO, the results showed that β3-AR level in the patients with phasic DO was significantly higher than that of the controls and terminal DO (Both P < 0.05). PGP9.5 and P₂  X ₃ levels were also significantly increased in phasic DO subgroup than controls. P₂  X ₃ receptor was positively correlated with PGP9.5 and β3-AR, and negatively correlated with the first sensation of bladder filling and voided volume in phasic DO.

CONCLUSIONS

Similar expression M3 receptor and increased P₂  X ₃ levels in phasic DO, compared with the controls, indicate that dysregulation of purinergic bladder signaling may contribute to the pathogenesis of phasic DO refractory to antimuscarinics. Elevated expression of β3-AR in phasic DO but not in terminal DO patients may explain the different urodynamic characteristics of DO between the two subgroups. Our findings suggest that β3-AR agonist or P₂  X ₃ antagonist might be a good treatment choice for patients with phasic DO refractory to antimuscarinic therapy.

Combined low-dose antimuscarinics for refractory detrusor overactivity in children

INTRODUCTION AND AIMS

Behavioral therapy and bowel management are the initial and mainstay treatments for overactive bladder (OAB). Antimuscarinic agents are initiated if these measures fail or symptoms are severe. This study reported the results of treatment with a high dosage of a single drug in children with refractory detrusor overactivity (DO). After the children maintained their previous antimuscarinic medication, a second antimuscarinic drug (trospium chloride) was added as a combination therapy.

MATERIALS AND METHOD

Seventy-two children with DO were enrolled in this prospective study (Figure). They had persistent urgency and urgency urinary incontinence (UUI), even with behavioral bowel therapy, and used an optimized dosage of oxybutynine. All patients demonstrated DO at urodynamic study and started on oxybutynin and trospium chloride at the lowest weight-adjusted dose (10-20 mg/day for trospium chloride). A bladder diary was recorded for 3 days, and urodynamic studies were repeated at 3 and 6 months.

RESULTS

Sixteen children (22.2%) became dry. Thirty-three children (45.8%) attained a significant decrease in incontinence from an average of 5 to 1.3 episodes per day. A statistically significant increase of mean cystometeric bladder capacity (P = 0.006) was also observed at the 6-month follow-up. The overall success rate was 68%, since 23 children (32%) discontinued combined treatment due to persistent symptoms and/or intolerable side effects. A total of 41 children (57%) reported no side effects, 25 (34.7%) reported mild side effects, six (8.3%) reported moderate side effects, and two withdrew from the study due to their side effects.

CONCLUSIONS

The addition of low-dose trospium chloride to oxybutynine seemed to be an effective and safe treatment approach for children with DO who were refractory to high-dosage monotherapy. Different combinations with different antimuscarinics drugs could be evaluated in the future.

Is pretreatment cystometry important in predicting response to mirabegron in women with overactive bladder symptoms?

INTRODUCTION AND HYPOTHESIS

The aim of this study was to evaluate for any association between pretreatment cystometry results and outcome of treatment with mirabegron in women with overactive bladder (OAB) symptoms.

METHODS

This was a prospective observational study of women with OAB symptoms that proved refractory to conservative management. All women underwent filling and voiding subtraction cystometry prior to further treatment. Women were treated with mirabegron 50 mg once daily, and outcomes were evaluated after 6 weeks' treatment. The primary outcome measure was change in symptoms as indicated by response to the Patient Global Impression of Improvement (PGI-I) scale. The presence of detrusor overactivity (DO), the highest detrusor pressure recorded during the filling phase, the presence of urodynamic stress incontinence (USI), cystometric capacity, voided volume, maximum flow rate and detrusor pressure at maximum flow were all compared between responders and nonresponders.

RESULTS

The study population consisted of 169 women; response rate to mirabegron was 69.8 %. There was no association between the presence of DO or maximum detrusor pressure during filling and USI, cystometric capacity, maximum flow rate and detrusor pressure at maximum flow and treatment response. In a subgroup with OAB symptoms refractory to previous treatment with antimuscarinics, there was an association between the presence of DO and a positive treatment response (p = 0.02).

CONCLUSIONS

Overall, there is no association between urodynamic findings and response to treatment with mirabegron. This may reflect the fact that mirabegron's mode of action mechanisms are not measurable using cystometry. In women with refractory symptoms, however, the presence of DO is associated with a positive response to treatment.

Oral pharmacotherapy for overactive bladder in older patients: mirabegron as a potential alternative to antimuscarinics

OBJECTIVE

Overactive bladder (OAB) is a particular challenge to treat in older adults with co-morbid conditions taking multiple medications. Antimuscarinics (e.g., solifenacin, fesoterodine) and β3-adrenergic receptor agonists (mirabegron) are similarly efficacious; however, antimuscarinics may be associated with side effects that result in poor persistence and contribute to anticholinergic burden, particularly in those taking other medications with anticholinergic properties. With a mechanism of action distinct from antimuscarinics, mirabegron has a different tolerability profile and does not contribute to anticholinergic burden. The objective of this review was to compare and contrast the tolerability profiles of antimuscarinics and mirabegron in older patients to inform practice.

METHODS

Prospective trials or retrospective subgroup analyses of antimuscarinics for the treatment of OAB in older patients were identified through a search of PubMed. Tolerability data and results of subgroup analyses of mirabegron in patients aged ≥65 and ≥75 years from a pooled analysis of three trials each of 12 weeks and a 1 year trial are described.

RESULTS

Anticholinergic adverse events (AEs) including dry mouth and constipation were more frequent with antimuscarinics versus mirabegron. In patients aged ≥65 years, dry mouth occurred with a six-fold higher incidence with tolterodine extended-release (ER) 4 mg than with mirabegron 25 mg or 50 mg over 12 weeks, and a three-fold higher incidence with tolterodine ER than mirabegron 50 mg over 1 year. Mirabegron had a low incidence of central nervous system effects. A systematic review of the cardiovascular safety profile of mirabegron has not identified any clinically significant effects on blood pressure or pulse rate at therapeutic doses amongst patients aged ≥65 years.

CONCLUSIONS

Mirabegron has a more favorable tolerability profile than antimuscarinics amongst older patients and may provide an improved benefit-to-risk ratio and therefore be considered as an alternative to antimuscarinics for older patients.

OnabotulinumtoxinA Treatment for Overactive Bladder in the Elderly: Practical Points and Future Prospects

Overactive bladder (OAB) increases with age. OAB in the elderly may be associated with increased risks of falls, fractures and mortality. Degeneration of the central nervous system in the elderly is proposed as one of the pathogenic factors for OAB. Recently, onabotulinumtoxinA (BoNT-A) 100 U has been demonstrated to be well tolerated, and it significantly improves all OAB symptoms and health-related quality of life in patients who are inadequately managed with anticholinergics. However, an increased risk of a large post-void residual volume and a lower long-term success rate were noted in frail elderly patients. Careful patient selection for BoNT-A injection treatment is important in elderly OAB patients. Patients who are frail, are elderly, have comorbidity or have a post-void residual volume >100 mL should be monitored carefully after BoNT-A injection treatment to prevent urinary retention and subsequent urinary tract infection. Use of liposomes to carry BoNT-A across the urothelial barrier decreases urgency-frequency episodes without compromising detrusor contractility and might avoid urinary tract infection. This treatment might prevent undesired detrusor underactivity after BoNT-A injection treatment, especially in elderly patients who have low detrusor contractility. For treatment of OAB in the elderly, clinicians should be aware of the balance between therapeutic efficacy and safety.

Neural control of micturition in humans: a working model

Results from functional brain scanning have shown that neural control of the bladder involves many different regions. Yet, many aspects of this complex system can be simplified to a working model in which a few forebrain circuits, acting mainly on the midbrain periaqueductal grey (PAG), advance or delay the triggering of the voiding reflex and generate bladder sensations according to the volume of urine in the bladder, the safety of voiding and the emotional and social propriety of doing so. Understanding these circuits seems to offer a route to treatment of conditions, such as urgency incontinence or overactive bladder, in patients without overt neurological disease. Two of these circuits include, respectively, the medial prefrontal cortex and the parahippocampal complex, as well as the PAG. These circuits belong to a well-known network that is active at rest and deactivated when attention is required. Another circuit, comprising the insula and the midcingulate or dorsal anterior cingulate cortex, is activated by bladder filling and belongs to a salience network that generates sensations such as the desire to void. Behavioural treatments of urgency incontinence lead to changes in brain function that support the working model and suggest the mechanism of this type of treatment.

Therapeutic Potential of Human Chorionic Gonadotropin Against Overactive Bladder

Overactive bladder (OAB) is a common form of urinary incontinence, resulting from spontaneous and random contractions of the urinary bladder. The affected individuals have an uncontrollable urge to urinate and experience incontinence and nocturia, which can greatly reduce the quality of daily life. There are several drugs for the treatment, and all of them have serious side effects. The following findings suggested that human chorionic gonadotropin (hCG) has a therapeutic potential that is worth investigating for the treatment of OAB. The finding are (1) human detrusor muscle contains hCG receptors, (2) detrusor muscle becomes quiescent during pregnancy, (3) hCG can inhibit detrusor muscle contractions induced by cholinergic stimulation in rats, and (4) hCG can mimic the anticholinergic drug on detrusor muscle contractions.

[The ice water test and bladder cooling reflex. Physiology, pathophysiology and clinical importance]

BACKGROUND

Urodynamic studies are utilised for identification and follow-up of functional disorders of the lower urinary tract. Provocation tests are used to determine disorders which could not be revealed in standard cystometry. The ice water test is a simple test to identify neurogenic bladder dysfunction and to screen the integrity of the upper motor neuron in neurogenic bladder dysfunction.

OBJECTIVES

Development and significance of the ice water test is presented in this review against the background of physiology and pathophysiology of the lower urinary tract.

MATERIALS AND METHODS

A systematic review of PubMed and ScienceDirect databases was performed in April 2015. No language or time limitation was applied. The following key words and Medical Subject Heading terms were used to identify relevant studies: "ice water test", "bladder cooling reflex", "micturition" and "neuronal control". Review articles and bibliographies of other relevant studies identified were hand searched to find additional studies.

RESULTS

The ice water test is performed by rapid instillation of 4-8 °C cold fluid into the urinary bladder. Hereby, afferent C fibers are activated by cold receptors in the bladder leading to the bladder cooling reflex. It is a spinal reflex which causes an involuntarily contraction of the urinary bladder. The test is normally positive in young infants during the first 4 years of life and become negative with maturation of the central nervous system afterwards by inhibition of the reflex. The damage of the upper motor neuron causes the recurrence of the reflex in the adulthood and indicates spinal and cerebral lesions.

DISCUSSION

The ice water test is utilised to identify lesions of the upper motor neuron. However, in the case of detrusor acontractility the test will always be negative and can not be utilized to distinguish between neurogenic or muscular causes. Furthermore, the test is also positive in a small percentage of cases of non-neurogenic diseases, e.g. in prostate-related bladder outlet obstruction or idiopathic overactive bladder. Although no clear explanation exists, a positive ice water test could be the first sign of an otherwise asymptomatic neurological disease.

CONCLUSIONS

Due to the simple procedure, the ice water test is a reliable possibility to identify neurologic bladder hyperactivity subsequent to standard cystometry.

[Physiopathology of overactive bladder syndrome]

The pathophysiology of OAB is complex, multifactorial and still largely unknown. Several pathophysiological mechanisms have been highlighted that may play a different role in different patient groups. There are now experimental evidences that support both the myogenic and neurogenic hypothesis, but in recent years the "integrative" hypothesis has been gaining more and more acceptance, where a disruption in the multiple interactions between different cell types (neurons, urothelium, interstitial cells, myocytes) and network functions represent a central element of lower urinary tract dysfunctions. Of utmost importance, a disorder in the urothelial sensory function and in the urothelial/suburothelial non-neural cholinergic system, favored by age and comorbidities, appears to be crucial for the development of the OAB. Neuroplastic and detrusor changes in OAB are broadly similar to those observed in bladders exposed to outlet obstruction, neuropathies, inflammation or aging, and may be driven by a common urothelial dysfunction. Several signaling substances and their receptors were found to be involved in central pathways of bidirectional communication between the different cell types in the bladder, and were shown to be modified in several animal models of OAB as well as in human models, indicating new potential therapeutic targets.

Investigating detrusor muscle concentrations of oxybutynin after intravesical delivery in an ex vivo porcine model

Intravesical oxybutynin is highly effective in the treatment of overactive bladder. Traditionally the mechanism of action was explained by antagonism of muscarinic receptors located in the detrusor, however evidence now suggests antimuscarinics may elicit their effect by modifying afferent pathways in the mucosal region. This study aimed to investigate the bladder wall distribution of oxybutynin in an ex vivo setting providing tissue - layer specific concentrations of drug achieved after intravesical delivery. Whole ex vivo porcine bladders were intravesically instilled with 0.167 mg mL(-1) oxybutynin solution. After 60 min, tissue samples were excised, serially sectioned parallel to the urothelial surface and extracted drug quantified. Drug distribution into the urothelium, lamina propria and detrusor was determined. Oxybutynin permeated into the bladder wall at a higher rate than other drugs previously investigated (apparent transurothelial Kp = 1.36 × 10(-5) cm s(-1) ). After 60 min intravesical instillation, concentrations achieved in the urothelium (298.69 μg g(-1) ) and lamina propria (43.65 μg g(-1) ) but not the detrusor (0.93 μg g(-1) ) were greater than reported IC50 values for oxybutynin. This work adds to the increasing body of evidence suggesting antimuscarinics elicit their effects via mechanisms other than direct inhibition of detrusor contraction.

Role of Nicotinic Acetylcholine Receptor α3 and α7 Subunits in Detrusor Overactivity Induced by Partial Bladder Outlet Obstruction in Rats

Purpose:

To investigate the role of α3 and α7 nicotinic acetylcholine receptor subunits (nAChRs) in the bladder, using a rat model with detrusor overactivity induced by partial bladder outlet obstruction (BOO).

Methods:

Forty Sprague-Dawley rats were used: 10 were sham-operated (control group) and 30 were observed for 3 weeks after partial BOO. BOO-induced rats were further divided into 3 groups: Two groups of 10 rats each received intravesicular infusions with hexamethonium (HM group; n=10) or methyllycaconitine (MLC group; n=10), which are antagonists for α3 and α7 nAChRs, respectively. The remaining BOO-induced rats received only saline infusion (BOO group; n=10). Based on the contraction interval measurements using cystometrogram, the contraction pressure and nonvoiding bladder contractions were compared between the control and the three BOO-induced groups. Immunofluorescent staining and Western blotting were used to analyze α3 and α7 nAChRs levels.

Results:

The contraction interval of the MLC group was higher than that of the BOO group (P<0.05). Nonvoiding bladder contraction almost disappeared in the HM and MLC groups. Contraction pressure increased in the BOO group (P<0.05) compared with the control group and decreased in the HM and MLC groups compared with the BOO group (P<0.05). Immunofluorescence staining showed that the α3 nAChR signals increased in the urothelium, and the α7 nAChR signals increased in the urothelium and detrusor muscle of the BOO group compared with the control group. Western blot analysis showed that both α3 and α7 nAChR levels increased in the BOO group (P<0.05).

Conclusions:

Alpha3 and α7 nAChRs are associated with detrusor overactivity induced by BOO. Furthermore, nAChR antagonists could help in clinically improving detrusor overactivity.

Management of nocturia in the female

Nocturia is a common but overlooked lower urinary tract symptom that substantially reduces patient health and quality of life. Though traditionally viewed as occurring predominantly in males, nocturia has been found to be equally as prevalent in females. The recent emphasis on the importance of nocturia has resulted in a surge of research studies, providing a foundation for current and future management decisions. In this review, we describe the current recommendations for the female patient in light of the most recently published studies, including a unique interest in predicting treatment response.

Understanding clinic options for overactive bladder

Overactive bladder (OAB) is a symptom complex of urinary frequency, nocturia and urgency with or without urgency incontinence that adversely impacts patient's quality of life. Conservative management begins in the outpatient clinic, often with significant improvement and patient satisfaction. In this review we will discuss the evaluation of OAB and review treatment options focusing on behavioral modification, medical therapy, and neuromodulation. These treatment options are offered in a stepwise fashion, remembering that more than one may be needed and can be used concomitantly.

Rationale for the use of prostaglandins and phosphodiesterase inhibitors in the treatment of functional bladder disorders

In this paper a general discussion of the available data on the role of prostaglandin (PG) and phosphodiesterase is discussed. Functional studies would be a next step to understand the functional meaning of the data described in this paper. The data presented are a basis for further research on selective modulation of the EP1 and EP2 receptor which could be a therapeutic target in functional bladder disorders such as OAB. PDE inhibitors are closer to clinical use, as these drugs have been studied and registered for other indications such as erectile dysfunction in men. Therefore, in vivo studies in human subjects can be conducted on short term. However, from a scientific point of view, it is very important to unravel the exact site of action and role of PDE inhibition with in vitro and in vivo studies as is the case with PG. In this way, a combination of drugs targeting different mechanisms involved in bladder physiology such as PG, cGMP, cAMP, and muscarinic receptors, could reduce side effects and improve efficacy.

Non-Hormonal treatment of BPH/BOO

OBJECTIVES

To review the use of non-hormonal pharmacotherapies in the treatment of lower urinary tract symptoms (LUTS) due to presumed benign prostatic hyperplasia (BPH).

MATERIALS AND METHODS

A search of the PUBMED database was conducted for the terms BPH, LUTS, bladder outlet obstruction, alpha-adrenoceptor blockers, anti-muscarinics, and phosphodiesterase-5-inhibitors.

RESULTS

Medical therapy has long been established as the accepted standard of care in the treatment of male LUTS. The aim of treatment is improvement in symptoms and quality of life whilst minimizing adverse effects. The agents most widely used as 1(st) line therapy are alpha-blockers (AB), as a standalone or in combination with 2 other classes of drug; 5-α reductase inhibitors and anti-muscarinics. AB have rapid efficacy, improving symptoms and flow rate in a matter of days, these effects are then maintained over time. AB do not impact on prostate size and do not prevent acute urinary retention or the need for surgery. Anti-mucarinics, alone or in combination with an AB are safe and efficacious in the treatment of bothersome storage symptoms associated with LUTS/BPH. Phosphodiesterase-5 inhibitors are an emerging treatment option that improve LUTS without improving flow rates.

CONCLUSIONS

AB are the most well-established pharmacotherapy in the management of men with LUTS/BPH. The emergence of different classes of agent offers the opportunity to target underlying pathophysiologies driving symptoms and better individualize treatment.

[Effect of distigmine at 5 mg daily in patients with detrusor underactivity]

PURPOSE

Since distigmine can cause the serious side effect of cholinergic crisis, its dosage regimen has been reduced to 5 mg/day for patients with difficulty in urination due to detrusor underactivity. Therefore, the efficacy and safety of add-on therapy with distigmine at 5 mg daily were examined in patients with persistent urination problems due to detrusor underactivity despite administration of alpha1-blockers.

PATIENTS AND METHODS

The subjects were 39 patients with underactive bladder (18 men and 21 women with an average age of 75 years) who showed no improvement of difficulty in urination or had a residual urine volume > or = 50 ml despite the administration of alpha1-blockers for more than 4 weeks. They received treatment with distigmine (5 mg daily after breakfast) in addition to their alpha1-blockers for 8 weeks. The international prostate symptom score (IPSS), quality-of-life (QOL) score, residual urine volume, blood pressure, and biochemistry tests were investigated before and after addition of distigmine.

RESULTS

After four and eight weeks of distigmine administration, all items of the IPSS and QOL score, as well as the residual urine volume, showed a significant decrease. In contrast, the pressure and pulse rate were unchanged. Serum creatinine showed a slight but significant decreased. As adverse events, frequent defecation, fecal incontinence, diarrhea, frequent urination and poor physical condition were recognized in 4 patients, but there was no serious event.

CONCLUSION

For difficulty in urination due to detrusor underactivity, the combination of an alpha1-blocker with distigmine at 5 mg daily showed early efficacy and good safety.

Bladder and erectile dysfunctions in the Type 2 diabetic Goto-Kakizaki rat

Despite the fact that urogenito-sexual complications significantly impact the quality of life of diabetic patients, a robust in vivo experimental model is lacking. Bladder and erectile function in the Type 2 diabetic Goto-Kakizaki (GK) rat and responses to standard-of-care treatments for each disorder have been assessed. GK rats (n = 25, 18-wk-old, GK/Par colony) and age-matched Wistar rats (n = 23), characterized for their metabolic parameters, were used. Bladder function was assessed by cystometry in conscious rats treated by intravenous solifenacin (1 mg/kg). Subsequently, erectile function was assessed under anesthesia following electrical stimulation of the cavernous nerve in presence of intravenous sildenafil (0.3 mg/kg). GK rats displayed detrusor overactivity with a significant increase in frequency/amplitude of nonvoiding contractions during the filling phase, together with an increase in bladder capacity, intercontraction interval, voided volume, and maximal pressure of voiding contraction. Solifenacin significantly decreased parameters characterizing voiding contractions without modifying voiding efficiency. Erectile function in GK rats was markedly impaired and remained so after sildenafil treatment despite a significant improvement. GK rats display both bladder and erectile dysfunctions and respond at least partially to standard-of-care treatments for each disorder, thus representing a suitable model to investigate the pathophysiology and assess the efficacy of new therapeutic agents for Type 2 diabetes-associated bladder and erectile complications.

Purinergic and muscarinic modulation of ATP release from the urothelium and its paracrine actions

The urothelium is a newly recognized sensory structure that detects bladder fullness. Pivotal to this sensory role is the release of ATP from the urothelium. However, the routes for urothelial ATP release, its modulation by receptor-mediated pathways, and the autocrine/paracrine role of ATP are poorly understood, especially in native tissue. We examined the action of key neurotransmitters: purinergic and muscarinic agonists on ATP release and its paracrine effect. Guinea pig and human urothelial mucosa were mounted in a perfusion trough; superfusate ATP was measured using a luciferin-luciferase assay, and tissue contractions were recorded with a tension transducer. Intracellular Ca²⁺ was measured in isolated urothelial cells with fura-2. The P2Y agonist UTP but not the P2X agonist α,β-methylene-ATP generated ATP release. The muscarinic agonist carbachol and the M₂-preferential agonist oxotremorine also generated ATP release, which was antagonized by the M₂-specific agent methoctramine. Agonist-evoked ATP release was accompanied by mucosal contractions. Urothelial ATP release was differentially mediated by intracellular Ca²⁺ release, cAMP, exocytosis, or connexins. Urothelium-attached smooth muscle exhibited spontaneous contractions that were augmented by subthreshold concentrations of carbachol, which had little direct effect on smooth muscle. This activity was attenuated by desensitizing P2X receptors on smooth muscle. Urothelial ATP release was increased in aging bladders. Purinergic and muscarinic agents produced similar effects in human urothelial tissue. This is the first demonstration of specific modulation of urothelial ATP release in native tissue by purinergic and muscarinic neurotransmitters via distinct mechanisms. Released ATP produces paracrine effects on underlying tissues. This process is altered during aging and has relevance to human bladder pathologies.

Evaluation of fesoterodine fumarate for the treatment of an overactive bladder

INTRODUCTION

Fesoterodine fumarate is an approved drug for overactive bladder. The aim of this study is to review the preclinical and most up to date clinical data on fesoterodine, with a special emphasis on its unique pharmacokinetic features and its implications on safety and tolerability in various patient populations.

AREAS COVERED

In this review, the authors extensively reviewed available literature via PubMed search regarding fesoterodine, covering its mechanism of action, pharmacodynamics and pharmacokinetics, clinical efficacy, safety, and tolerability.

EXPERT OPINION

Fesoterodine is an anti-muscarinic agent with a unique pharmacokinetic profile. It is a prodrug that is rapidly metabolized to its active form by nonspecific plasma esterases. Its metabolism is independent of the cytochrome P450 enzyme system. This along with its dual excretion pathways and minimal central nervous system penetration leads to less variability in drug exposure and allowance of administration in those with mild to moderate renal and hepatic insufficiency and in the geriatric population.

Combination of foot stimulation and tolterodine treatment eliminates bladder overactivity in cats

AIMS

To determine whether transcutaneous foot stimulation combined with a lower dose tolterodine would inhibit bladder overactivity more effectively than either treatment alone.

METHODS

Cystometrograms were performed on α-chloralose anesthetized cats (N = 6) by infusing 0.25% acetic acid (AA) to induce bladder overactivity. Foot stimulation (5 Hz) was applied at 2 and 4 times the threshold (T) intensity in volts (i.e., 2T or 4T) for inducing toe movement to inhibit bladder overactivity. Cumulative doses of tolterodine (0.003-0.3 mg/kg, i.v.) were also administered to determine the effect of combination treatment.

RESULTS

AA irritation of the bladder significantly (P < 0.0001) reduced bladder capacity to 23.6 ± 7.1% of saline control capacity. Foot stimulation alone at 2T and 4T inhibited bladder overactivity and significantly (P < 0.0001) increased bladder capacity to 50.7 ± 6.8% and 79.0 ± 11.6% of saline control, respectively. Tolterodine alone at 0.3 mg/kg significantly (P < 0.05) increased bladder capacity to 65.6 ± 15.5% of saline control. However, when tolterodine at a threshold dose (0.3 mg/kg) was combined with foot stimulation, the bladder capacity was significantly (P < 0.05) increased to 86.2 ± 6.2% and 107.9 ± 10.6% by 2T and 4T stimulation, respectively. Complete inhibition of bladder overactivity could be achieved at a lower tolterodine dose (0.1 mg/kg) when combined with 4T stimulation (97.0 ± 11.2% of saline control). The amplitude of micturition contraction was not changed by tolterodine treatment.

CONCLUSIONS

This study suggests a novel, efficacious, non-invasive therapy by combining foot stimulation with a lower dose tolterodine to treat bladder overactivity. It also provides the first objective evidence supporting an additive therapeutic benefit of neuromodulation and antimuscarinic combination treatment.

Combined antimuscarinics for treatment of neurogenic overactive bladder

Antimuscarinic drugs are the first line pharmacotherapy for overactive bladder, but they are not always effective to achieve complete continence. Nevertheless in some patients urodynamic investigations reveal insufficient effects with continuing incontinence events even with dose optimization. The aim of this study is to evaluate the effect of association of Oxybutynin chloride, Trospium chloride and Solifenacin succinate administered orally for a minimum of 12 weeks in subjects with suprasacral spinal cord injury with urge-incontinence, urodynamic–proven neurogenic detrusor overactivity dysfunction and detrusor-external sphincter dyssynergia to improve level of continence, reduce the risks of urologic complications and enhance QOL. This study was a randomized, double blind, controlled, balanced-parallel-groups investigation of orally administed Oxybutynin in addition to Trospium chloride in the first group and Oxybutynin in addition to Solifenacin in the other group. A total of 12 patients with neurogenic detrusor overactivity and clean intermittent catheterization were allocated into two treatment groups: 5 mg tablet of Oxibutinin and 20 mg tablet of Trospium Chloride were administered respectively 3 times a day and 4 times a day in the first group (Group A). 5 mg tablet of Oxibutinin and 10 mg tablet of Solifenacin were administered respective 3 times a day and once daily in the second group (Group B). In both group of patients we found a significant decrease in incontinence episodes, with an improvement of bladder compliance, bladder capacity and volume voided. Side effects were higher in patients of group B, but in generally well tolerated. In conclusion, a combined antimuscarinic treatment might be a right option for patients affected by neurogenic bladder refractory to previous antimuscarinic monotherapy, and might slow down or delay other more invasive treatments.

The effect of indomethacin on the muscarinic induced contractions in the isolated normal guinea pig urinary bladder

Background

To investigate the effect of prostaglandin depletion by means of COX-inhibition on cholinergic enhanced spontaneous contractions.

Methods

The urethra and bladder of 9 male guinea pigs (weight 270–300 g) were removed and placed in an organ bath with Krebs’ solution. A catheter was passed through the urethra through which the intravesical pressure was measured. The muscarinic agonist arecaidine, the non-selective COX inhibitor indomethacin, and PGE₂ were subsequently added to the organ bath. The initial average frequency and amplitude of spontaneous contractions in the first 2 minutes after arecaidine application were labelled F_ini and P_ini, respectively. The steady state frequency (F_steady) and amplitude (P_steady) were defined as the average frequency and amplitude during the 5 minutes before the next wash out.

Results

Application of 1 μM PGE₂ increased the amplitude of spontaneous contractions without affecting frequency. 10 μM of indomethacin reduced amplitude but not frequency.

The addition of indomethacin did not alter F_ini after the first application (p = 0.7665). However, after the second wash, F_ini was decreased (p = 0.0005). F_steady, P_steady and P_ini were not significantly different in any of the conditions. These effects of indomethacin were reversible by PGE₂ addition._.

Conclusions

Blocking PG synthesis decreased the cholinergically stimulated autonomous contractions in the isolated bladder. This suggests that PG could modify normal cholinergically evoked response. A combination of drugs inhibiting muscarinic receptors and PG function or production can then become an interesting focus of research on a treatment for overactive bladder syndrome.

Long-term safety, efficacy, and tolerability of imidafenacin in the treatment of overactive bladder: a review of the Japanese literature

Imidafenacin is an antimuscarinic agent with high affinity for the M(3) and M(1) muscarinic receptor subtypes and low affinity for the M(2) subtype, and is used to treat overactive bladder. Several animal studies have demonstrated that imidafenacin has organ selectivity for the bladder over the salivary glands, colon, heart, and brain. In Phase I studies in humans, the approximately 2.9-hour elimination half-life of imidafenacin was shorter than that of other antimuscarinics such as tolterodine and solifenacin. Imidafenacin was approved for clinical use in overactive bladder in Japan in 2007 after a randomized, double-blind, placebo-controlled Phase II study and a propiverine-controlled Phase III study conducted in Japanese patients demonstrated that imidafenacin 0.1 mg twice daily was clinically effective for treating overactive bladder and was not inferior to propiverine for reduction of episodes of incontinence, with a better safety profile than propiverine. Several short-term clinical studies have demonstrated that imidafenacin also improves sleep disorders, nocturia, and nocturia-related quality of life. In addition, it is speculated that addon therapy with imidafenacin is beneficial for men with benign prostatic hyperplasia whose overactive bladder symptoms are not controlled by alpha-1 adrenoceptor antagonists. No cognitive impairment or influence of imidafenacin on the QTc interval has been observed. Although there have been very few relevant long-term clinical studies, the available information suggests the long-term efficacy, safety, and tolerability of imidafenacin, with less frequent severe adverse events, such as dry mouth and constipation. In addition, imidafenacin can be used safely for a long time even for cognitively vulnerable elderly patients with symptoms of overactive bladder. Thus, it is highly likely that imidafenacin is safe, efficacious, and tolerable to control symptoms of overactive bladder even over the long term. However, it remains unknown if the practical effectiveness of imidafenacin is applicable to ethnic groups other than Japanese.

Coupled nitric oxide and autonomic receptor functional responses in the normal and inflamed urinary bladder of the rat

Both divisions of the autonomic nervous system are involved in regulation of urinary bladder function. Several substances, other than noradrenaline and acetylcholine, seem to play important roles in physiology and pathophysiology of lower urinary tract. In the current study, we aimed to examine if there exist interplays between nitric oxide (NO) and autonomic transmitters and if such interactions vary in different parts of the urinary bladder in healthy and cyclophosphamide (CYP)-induced cystitic rats; when administered to the animals (100 mg/kg; i.p.), the cytotoxic CYP metabolite acrolein induces bladder inflammation. In the current study a series of in vitro functional studies were performed on detrusor muscle strip preparations. Stimulation with electrical field stimulation (EFS), methacholine, adenosine 5´-triphosphate (ATP), and adrenaline evoked contractile responses in isolated bladder preparations that were significantly reduced in cyclophosphamide (CYP)-treated rats. While the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine (L-NNA; 10(-4) M) did not affect contractile responses in normal, healthy strip preparations, it significantly increased the contractile responses to EFS, methacholine and adrenaline, but not to ATP, in the bladders from the CYP-treated rats. In the CYP-treated rats, the ATP-evoked relaxatory part of its dual response (an initial contraction followed by a relaxation) was 6-fold increased in comparison with that of normal preparations, whereas the isoprenaline relaxation was halved in the CYP-treated. While L-NNA (10(-4) M) had no effect on the isoprenaline-evoked relaxations, it reduced the ATP-evoked relaxations in strip preparations from the bladder body of CYP-treated rats. Stimulation of beta(2)- and beta(3)-adrenoceptors evoked relaxations and both responses were reduced in cystitis, the latter to a larger extent. In the trigone, the reduced ATP-evoked contractile response in the inflamed strips was increased by L-NNA, while L-NNA had no effect on the ATP-evoked relaxations, neither on the relaxations in healthy nor on the larger relaxations in the inflamed trigone. The study shows that both contractile and relaxatory functions are altered in the state of inflammation. The parasympathetic nerve-mediated contractions of the body of the bladder, evoked by the release of ATP and acetylcholine, were substantially reduced in cystitis. The relaxations to beta-adrenoceptor and purinoceptor stimulation were also reduced but only the ATP-evoked relaxation involved NO.