Multiple intravesical instillation of low-dose resiniferatoxin is effective in the treatment of detrusor overactivity refractory to anticholinergics

Resiniferatoxin: Nature's Precision Medicine to Silence TRPV1-Positive Afferents

Resiniferatoxin (RTX) is an ultrapotent capsaicin analog with a unique spectrum of pharmacological actions. The therapeutic window of RTX is broad, allowing for the full desensitization of pain perception and neurogenic inflammation without causing unacceptable side effects. Intravesical RTX was shown to restore continence in a subset of patients with idiopathic and neurogenic detrusor overactivity. RTX can also ablate sensory neurons as a "molecular scalpel" to achieve permanent analgesia. This targeted (intrathecal or epidural) RTX therapy holds great promise in cancer pain management. Intra-articular RTX is undergoing clinical trials to treat moderate-to-severe knee pain in patients with osteoarthritis. Similar targeted approaches may be useful in the management of post-operative pain or pain associated with severe burn injuries. The current state of this field is reviewed, from preclinical studies through veterinary medicine to clinical trials.

Interventional management and surgery of neurogenic lower urinary tract dysfunction in patients with chronic spinal cord injury: A urologist's perspective

Neurogenic lower urinary tract dysfunction (NLUTD) caused by spinal cord injury (SCI) is challenging for urologists. NLUTD not only affects the quality of life but also endangers the upper urinary tract of patients with chronic SCI. Considering that the bladder and urethral function change with time, regular follow-up of NLUTD is necessary, and any complication should be adequately treated. The first priority of bladder management in patients with chronic SCI manifesting NLUTD should be renal function preservation, followed by the normalization of lower urinary tract function. The quality of life should also be assessed. Patients who have a high risk for impaired renal function should be more frequently identified and investigated. Conservative treatment and pharmacological therapy should be started as early as possible. Intravesical or urethral injections of botulinum toxin A is an alternative treatment for refractory NLUTD. When surgical intervention is necessary, less invasive and reversible procedures should be considered first. Improving patients' quality of life and willingness to undergo bladder management is the most important aspect of treatment.

Using Botulinum Toxin A for Treatment of Interstitial Cystitis/Bladder Pain Syndrome-Possible Pathomechanisms and Practical Issues

Treatment for patients with interstitial cystitis/bladder pain syndrome (IC/BPS) is always challenging for urologists. The main mechanism of the botulinum toxin A (BoNT-A) is inhibition of muscle contraction, but the indirect sensory modulation and anti-inflammatory effect in the bladder also play important roles in treating patients with IC/BPS. Although current guidelines consider BoNT-A injection to be a standard treatment, some practical issues remain debatable. Most clinical evidence of this treatment comes from retrospective uncontrolled studies, and only two randomized placebo-control studies with limited patient numbers have been published. Although 100 U BoNT-A is effective for most patients with IC/BPS, the potential efficacy of 200 U BoNT-A has not been evaluated. Both trigone and diffuse body BoNT-A injections are effective and safe for IC/BPS, although comparison studies are lacking. For IC/BPS patients with Hunner’s lesion, the efficacy of BoNT-A injection remains controversial. Most patients with IC/BPS experience symptomatic relapse at six to nine months after a BoNT-A injection, although repeated injections exhibit a persistent therapeutic effect in long-term follow-up. Further randomized placebo-controlled studies with a larger number of patients are needed to support BoNT-A as standard treatment for patients with IC/BPS.

Potential therapeutic value of transient receptor potential channels in male urogenital system

Transient receptor potential (TRP) channels comprise a family of cation channels implicated in a variety of cellular processes including light, mechanical or chemical stimuli, temperature, pH, or osmolarity. TRP channel proteins are a diverse family of proteins that are expressed in many tissues. We debated our recent knowledge about the expression, function, and regulation of TRP channels in the different parts of the male urogenital system in health and disease. Emerging evidence suggests that dysfunction of TRP channels significantly contributes to the pathophysiology of urogenital diseases. So far, there are many efforts underway to determine if these channels can be used as drug targets to reverse declines in male urogenital function. Furthermore, developing safe and efficacious TRP channel modulators is warranted for male urogenital disorders in a clinical setting.

Characterization of muscarinic and P2X receptors in the urothelium and detrusor muscle of the rat bladder

Muscarinic and purinergic (P2X) receptors play critical roles in bladder urothelium under physiological and pathological conditions. Aim of present study was to characterize these receptors in rat bladder urothelium and detrusor muscle using selective radioligands of [N-methyl-(3)H]scopolamine methyl chloride ([(3)H]NMS) and αβ-methylene ATP [2,8-(3)H]tetrasodium salt ([(3)H]αβ-MeATP). Similar binding parameters for each radioligand were observed in urothelium and detrusor muscle. Pretreatment with N-(2-chloroethyl)-4-piperidinyl diphenylacetate (4-DAMP mustard) mustard revealed co-existence of M2 and M3 receptors, with the number of M2 receptors being larger in the urothelium and detrusor muscle. Intravesical administration of imidafenacin and Dpr-P-4 (N → O) (active metabolite of propiverine) displayed significant binding of muscarinic receptors in the urothelium and detrusor muscle. The treatment with cyclophosphamide (CYP) or resiniferatoxin (RTX) resulted in a significant decrease in maximal number of binding sites (Bmax) for [(3)H]NMS and/or [(3)H]αβ-MeATP in the urothelium and detrusor muscle. These results demonstrated that 1) pharmacological characteristics of muscarinic and P2X receptors in rat bladder urothelium were similar to those in the detrusor muscle, 2) that densities of these receptors were significantly altered by pretreatments with CYP and RTX, and 3) that these receptors may be pharmacologically affected by imidafenacin and Dpr-P-4 (N → O) which are excreted in the urine.

[Therapy of overactive bladder (OAB)]

Overactive bladder (OAB) is a symptom complex which is present in approximately 17% of the European population. It is observed in the presence or absence of incontinence (wet or dry) and is associated with a high degree of psychological stress as well as high costs for the healthcare system. Myogenic, urothelial and neurogenic factors lead to frequently unknown changes of muscular, neural and connective tissue. For the definition, etiology and diagnostics of the disease the previous continuing medical education (CME) article "Diagnosis of overactive bladder (OAB)" should be consulted. In recent years some improvements have been made in OAB-related research, in terms of pathophysiological models and new pharmacological approaches with the development of new therapeutic agents. Besides classical substances, recently approved agents are increasingly being used for the therapy of OAB. Furthermore, non-pharmaceutical approaches and surgical techniques still play an important role in the therapy of OAB.

TRP channels in lower urinary tract dysfunction

Lower urinary tract dysfunction (LUTd) represents a major healthcare problem. Although it is mostly not lethal, associated social disturbance, medical costs, loss of productivity and especially diminished quality of life should not be underestimated. Although more than 15% of people suffer from a form of LUTd to some extent, pathophysiology often remains obscure. In the past 20 years, transient receptor potential (TRP) channels have become increasingly important in this field of research. These intriguing ion channels are believed to be the main molecular sensors that generate bladder sensation. Therefore, they are intensely pursued as new drug targets for both curative and symptomatic treatment of different forms of LUTd. TRPV1 was the first of its class to be investigated. Actually, even before this channel was cloned, it had already been targeted in the bladder, with clinical trials of intravesical capsaicin instillations. Several other polymodally gated TRP channels, particularly TRPM8, TRPA1 and TRPV4, also appear to play a prominent role in bladder (patho)physiology. With this review, we provide a brief overview of current knowledge on the role of these TRP channels in LUTd and their potential as molecular targets for treatment.

New therapies in the treatment of overactive bladder

INTRODUCTION

Overactive bladder (OAB) is a common condition which affects both men and women across many age groups with significant impact on quality of life. There is currently an armamentarium of treatment options available ranging from conservative, medical therapy to radical surgeries. Increasing understanding of OAB is resulting in the rapid development of new therapies today.

AREAS COVERED

The purpose of this article was to summarise the latest developments in non-neurogenic OAB treatment, discuss the evidence and results of current and new treatment modalities available through review of published data and results presented at recent international meetings.

EXPERT OPINION

The ultimate goal in OAB therapy is to provide good clinical efficacy, safe, non-invasive and easy to administer. There is definitely room for development of new therapies in OAB and current progress is encouraging.

Modulation of urinary bladder innervation: TRPV1 and botulinum toxin A

The persisting interest around neurotoxins such as vanilloids and botulinum toxin (BoNT) derives from their marked effect on detrusor overactivity refractory to conventional antimuscarinic treatments. In addition, both are administered by intravesical route. This offers three potential advantages. First, intravesical therapy is an easy way to provide high concentrations of pharmacological agents in the bladder tissue without causing unsuitable levels in other organs. Second, drugs effective on the bladder, but inappropriate for systemic administration, can be safely used as it is the case of vanilloids and BoNT. Third, the effects of one single treatment might be extremely longlasting, contributing to render these therapies highly attractive to patients despite the fact that the reasons to the prolonged effect are still incompletely understood. Attractive as it may be, intravesical pharmacological therapy should still be considered as a second-line treatment in patients refractory to conventional oral antimuscarinic therapy or who do not tolerate its systemic side effects. However, the increasing off-label use of these neurotoxins justifies a reappraisal of their pharmacological properties.

LUTS treatment: Future treatment options

Lower urinary tract symptoms (LUTS) are commonly divided into storage, voiding, and postmicturition symptoms, and may occur in both men and women. Male LUTS have historically been linked to benign prostatic hyperplasia (BPH), but are not necessarily prostate related. The focus of treatment for LUTS has thus shifted from the prostate to the bladder and other extraprostatic sites. LUTS include symptoms of the overactive bladder (OAB), which are often associated with detrusor overactivity. Treatment for LUTS suggestive of BPH has traditionally involved the use of alpha(1)-adrenoceptor (AR) antagonists; 5alpha-reductase inhibitors; and phytotherapy-however, several new therapeutic principles have shown promise. Selective beta(3)-adrenoceptor agonists and antimuscarinics are potentially useful agents for treating LUTS, particularly for storage symptoms secondary to outflow obstruction. Other agents of potential or actual importance are antagonists of P2X(3) receptors, botulinum toxin type A, endothelin (ET)-converting enzyme inhibitors, and drugs acting at vanilloid, angiotensin, and vitamin D(3) receptor sites. Drugs interfering with the nitric oxide/cGMP-cAMP pathway, Rho-kinase and COX inhibitors, as well as drugs targeting receptors and mechanisms within the CNS, are also of interest and deserving of further study for the treatment of LUTS.

Intravesikale Therapie des Overactive-bladder-Syndroms

Overactive bladder and urgency incontinence are common conditions generally treated with oral anticholinergic medication. Despite the development of new antimuscarinic substances, many patients are refractory to or cannot tolerate the oral therapy due to severe side effects. Intravesical instillation therapy can provide an alternative method to manage detrusor overactivity. Intravesical instillation of anticholinergics such as oxybutynin and trospium chloride can achieve cholinergic blockade without producing systemic side effects. Botulinum toxin type A injections into the detrusor have been shown to increase bladder capacity and to decrease detrusor overactivity for 6 or more months. Intravesical local anesthetics such as lidocaine and bupivacaine block the conduction of unmyelinated C fibers which results in an increase of functional bladder capacity. Intravesical capsaicin and resiniferatoxin also affect the afferent C fiber innervation of the bladder, leading to a decrease in detrusor overactivity and also an increased bladder capacity. The use of intravesical anticholinergics and of local anesthetic medications, both known for their short-term efficacy, is limited due to the necessity of daily intermittent catheterization. In conclusion, intravesical therapies can provide an alternative treatment for the management of overactive bladder.

Evaluation and management of refractory overactive bladder

The refractory overactive bladder patient is a complex new entity for the urologic community. We present the most current review of this difficult subject matter with an emphasis on evaluation and new treatment options such as sacral neuromodulation and botulinum toxin injection. It is hoped that in this new era of medical innovation, extirpation and reconstruction of the bladder will become historic in nature and refractory therapy can be transitioned to the office and outpatient operation rooms.

Neuromodulatory therapies in female pelvic medicine and reconstructive surgery: biological agents

In recent years, important improvements in the management of patients with neurogenic or non-neurogenic detrusor overactivity and urge incontinence have been brought about by the introduction of vanilloids and botulinum toxins in urology. In this review we introduce the new therapeutic options, provides basic information, and summarize the results experienced so far.

Therapeutic effect of multiple resiniferatoxin intravesical instillations in patients with refractory detrusor overactivity: a randomized, double-blind, placebo controlled study

PURPOSE

Previous study has shown that multiple intravesical instillations of resiniferatoxin (Sigma) at 10 nM has therapeutic effects in patients with detrusor overactivity. To our knowledge the placebo effect of multiple instillations of low dose resiniferatoxin for neurogenic and nonneurogenic detrusor overactivity has not been investigated. In this randomized, double-blind, placebo controlled study we evaluated the therapeutic effects of this resiniferatoxin treatment.

MATERIALS AND METHODS

A total of 54 patients with detrusor overactivity refractory to anticholinergics were enrolled and randomly treated with 4 weekly intravesical instillations of 10 nM resiniferatoxin (26) or vehicle, consisting of 10% ethanol in normal saline, as the control group (28). The clinical effects of treatment on incontinence grade, incontinence episodes, general satisfaction, lower urinary tract symptoms and urodynamic parameters were assessed.

RESULTS

Three months after completing the 4 intravesical treatments the resiniferatoxin treatment group had a significantly higher percent of patients with excellent and improved results compared to the control group (19.2% vs 7.1% and 42.3% vs 14.2%, respectively, each p < 0.001). Treatment remained effective at 6 months in 13 patients (50%) in the resiniferatoxin group but in only 3 (11%) in the control group (p < 0.001). Bladder capacity was significantly increased and symptom scores significantly improved 3 months after treatment in the resiniferatoxin group but not in the control group.

CONCLUSIONS

Multiple intravesical instillations of 10 nM resiniferatoxin were effective for improving the incontinence grade in 62% of patients at 3 months, of whom 50% maintained a therapeutic effect 6 months after treatment. The therapeutic effect of resiniferatoxin was significantly superior to that of placebo.

The overactive bladder: review of current pharmacotherapy in adults. Part 2: treatment options in cases refractory to anticholinergics

In the first part of this review the potential pathophysiological factors involved in the overactive bladder were outlined, and the wide range of first-line anticholinergic pharmacotherapies available for such patients were reviewed. The second part will focus on the intravesical instillation of resiniferatoxin and injections of botulinum toxin into the bladder to treat overactive bladder and detrusor overactivity. Resiniferatoxin has been shown to increase bladder capacity and improve incontinence in patients with neurogenic and non-neurogenic detrusor overactivity. Botulinum toxin has successfully been used to treat neurogenic and idiopathic detrusor overactivity, with improvements observed in bladder capacity, decreases in detrusor pressures on filling and voiding, and increased volumes at first contraction. Further validation is required for both treatments, in the form of large randomised controlled trials, before their use can be considered routine, with particular focus on dosing required.

The Rationale of Dual Serotonin/Noradrenaline Reuptake Inhibitors in the Management of Stress Urinary Incontinence

This paper aims at evaluating the role of serotonin (5-HT) and noradrenaline in the nervous control of urinary continence. Both α1-adrenergic and 5-HT2 receptors in the Onuf's nucleus help the guarding reflex; therefore the pharmacologic agents enhancing the effects of 5-HT and noradrenaline represent a promising choice in treating stress urinary incontinence. Duloxetine, a dual 5-HT/noradrenaline reuptake inhibitor, improves the external urethral sphincter contractility while increasing the activation of 5-HT2 and α1-adrenergic receptors thanks to the high concentrations of these monoamines in the Onuf's nucleus; it also plays a significant role in the management of stress urinary incontinence.