Urodynamic effects of intravesical resiniferatoxin in humans: preliminary results in stable and unstable detrusor

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.

Molecular Surgery Concept from Bench to Bedside: A Focus on TRPV1+ Pain-Sensing Neurons

"Molecular neurosurgery" is emerging as a new medical concept, and is the combination of two partners: (i) a molecular neurosurgery agent, and (ii) the cognate receptor whose activation results in the selective elimination of a specific subset of neurons in which this receptor is endogenously expressed. In general, a molecular surgery agent is a selective and potent ligand, and the target is a specific cell type whose elimination is desired through the molecular surgery procedure. These target cells have the highest innate sensitivity to the molecular surgery agent usually due to the highest receptor density being in their plasma membrane. The interaction between the ligand and its receptor evokes an overactivity of the receptor. If the receptor is a ligand-activated non-selective cation channel, the overactivity of receptor leads to excess Ca²⁺ and Na⁺ influx into the cell and finally cell death. One of the best known examples of such an interaction is the effect of ultrapotent vanilloids on TRPV1-expressing pain-sensing neurons. One intrathecal resiniferatoxin (RTX) dose allows for the receptor-mediated removal of TRPV1+ neurons from the peripheral nervous system. The TRPV1 receptor-mediated ion influx induces necrotic processes, but only in pain-sensing neurons, and usually within an hour. Besides that, target-specific apoptotic processes are also induced. Thus, as a nano-surgery scalpel, RTX removes the neurons responsible for generating pain and inflammation from the peripheral nervous system providing an option in clinical management for the treatment of morphine-insensitive pain conditions. In the future, the molecular surgery concept can also be exploited in cancer research for selectively targeting the specific tumor cell.

Bladder cancer and urothelial impairment: the role of TRPV1 as potential drug target

Urothelium, in addition to its primary function of barrier, is now understood to act as a complex system of cell communication that exhibits specialized sensory properties in the regulation of physiological or pathological stimuli. Furthermore, it has been hypothesized that bladder inflammation and neoplastic cell growth, the two most representative pathological conditions of the lower urinary tract, may arise from a primary defective urothelial lining. Transient receptor potential vanilloid channel 1 (TRPV1), a receptor widely distributed in lower urinary tract structures and involved in the physiological micturition reflex, was described to have a pathophysiological role in inflammatory conditions and in the genesis and development of urothelial cancer. In our opinion new compounds, such as curcumin, the major component of turmeric Curcuma longa, reported to potentiate the effects of the chemotherapeutic agents used in the management of recurrent urothelial cancer in vitro and also identified as one of several compounds to own the vanillyl structure required to work like a TRPV1 agonist, could be thought as complementary in the clinical management of both the recurrences and the inflammatory effects caused by the endoscopic resection or intravesical chemotherapy administration or could be combined with adjuvant agents to potentiate their antitumoral effect.

Standard Pharmacological Treatment and New Therapies for Overactive Bladder

The prevalence of overactive bladder (OAB) in adult males varies from 10.2% to 17.4%, and in females from 7.7 to 31.3. 16.5% of the adult population presents symptoms consistent with OAB; of these, 37.2% are actually affected. The OAB has a significant effect on the quality of life. Initial treatment includes behavioral therapy, physiotherapy and antimuscarinic drugs. In patients where behavioral modifications fail, treatment is associated with antimuscarinics. The antimuscarinic agents used to treat OAB showed some efficacy, but adverse events too, such as dry mouth, constipation, headache and blurred vision. In selected cases unresponsive to antimuscarinic therapy, it is possible to use second-line treatments represented by sacral neuromodulation and botulinum toxin type A both for idiopathic detrusor overactivity, where it is still an experimental treatment, and for neurogenic cases with 2011 FDA approval. Surgical options represent the last choice for selected cases.

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.

Transcutaneous electrical stimulation of urinary bladder in patients with spinal cord injuries

INTRODUCTION

The treatment of neurogenic dysfunctions of micturition, both surgical and conservative, aims primarily to protect upper urinary tract function. This goal can be achieved by lowering intravesical pressure and increasing urinary bladder capacity in the urine collection phase or by facilitating bladder emptying.

OBJECTIVE

The objective of this paper was to assess the outcome of transcutaneous stimulation of the urinary bladder in the treatment of neurogenic disorders of micturition.

MATERIALS AND METHODS

The effect of urinary bladder stimulation was assessed in 22 patients (4 females, 18 males) with spinal injuries (19 with injuries to the lumbo-sacral spine and 3 with cervical spine injuries) treated at the Department of Rehabilitation of the Military Hospital in Bydgoszcz, Poland, in 2006 and 2007. The treatment consisted of 30 procedures of transcutaneous electrical stimulation of the urinary bladder. A pulsed sinusoid current was used with a pulse duration of 200 ms, break duration of 1,000 ms, intensity of 15-20 mA, frequency of 50 Hz, and duration of stimulation of 15 min. A urodynamic study was carried out in each patient at baseline and on completion of the electrical stimulation therapy (immediately and after 2 months).

RESULTS

Electrical stimulation of the neurogenic urinary bladder produced increases in the cystometric bladder capacity and reduction in the amount of residual urine (72% of patients), with reduction of intravesical pressure at peak urine flow (59% of the patients). The dynamic aspects of micturition also improved with increased peak voiding velocity in 77.3% of the patients. More than half of the patients (57%) still had elevated intravesical pressures during micturition that posed a risk to the function of the upper urinary tract despite significant decreases following the stimulation therapy. Micturition, which was absent at baseline, was restored in three patients. No local complications were observed.

CONCLUSIONS

Transcutaneous electrical stimulation of the urinary bladder in patients with neurogenic bladder dysfunction improves lower urinary tract function. Urodynamic studies executed 2 months after finishing TES show persistent results.

Resiniferatoxin and botulinum toxin type A for treatment of lower urinary tract symptoms

Resiniferatoxin (RTX) and botulinum toxin subtype A (BTX-A) are increasingly viewed as potential treatments for lower urinary tract symptoms (LUTS) refractory to conventional therapy. RTX, a capsaicin analogue devoid of severe pungent properties, acts by desensitizing the transient receptor potential vanilloid type 1 (TRPV1) receptor and inactivating C-fibers. BTX-A cleaves soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins in afferent and efferent nerve endings, therefore impeding the fusion of synaptic vesicles with the neuronal membrane necessary for the release of neurotransmitters. In patients with neurogenic and idiopathic detrusor overactivity, RTX and BTX-A have been shown to increase the volume to first detrusor contraction, increase bladder capacity, and improve urinary incontinence and quality of life. Recent data also suggest a role for these neurotoxins in treating urgency, the primary symptom in overactive bladder (OAB) syndrome. Furthermore, experimental data strongly support the use of both neurotoxins in the treatment of pain and frequency in patients with interstitial cystitis/painful bladder syndrome (IC/PBS), although the results from available clinical trials for this use are still inconclusive. In spite of promising results overall, it should be made clear that the administration of these neurotoxins is still considered an experimental procedure and that more clinical studies are necessary before a license for their use will be issued by health authorities.

Anticholinergic drugs versus other medications for overactive bladder syndrome in adults

BACKGROUND

Overactive bladder syndrome is defined as "urgency with or without urge incontinence, usually with frequency and nocturia". It is a common condition with significant economic and quality of life implications. While the condition's pathophysiology remains to be fully elucidated, pharmacotherapy is the main treatment option. Despite uncertainty as to drug treatment of choice, anticholinergics are increasingly being used in primary and secondary care settings. This review compares anticholinergic drugs with other types or classes of drugs for treating overactive bladder syndromes.

OBJECTIVES

To compare anticholinergic drugs with other types or classes of drugs for treating overactive bladder symptoms.

SEARCH STRATEGY

We searched the Cochrane Incontinence Group Specialised Trials Register (searched 20 December 2006) and the reference lists of relevant articles. No language or other limits were imposed.

SELECTION CRITERIA

All randomised and quasi-randomised controlled trials comparing anticholinergic drugs with other drugs for the treatment of overactive bladder symptoms. At least one arm of the study used an anticholinergic drug and at least one other arm used a non-anticholinergic drug.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed the identified studies for eligibility and methodological quality and independently extracted data from the included studies. Data analysis was performed using RevMan software (version 4.2.8).

MAIN RESULTS

Twelve trials were included in the review. There were seven crossover trials and five parallel group studies. For the comparisons between anticholinergic drugs with tricyclic antidepressants, alpha adrenergic agonists, afferent nerve inhibitors, and calcium channel blocker a single trial was identified for each. Nine trials compared flavoxate with anticholinergics. There was no evidence of a difference in cure rates between anticholinergics and flavoxate. Adverse effects were more frequent in anticholinergic groups versus flavoxate groups (RR 2.28 95% CI 1.45 to 3.56). There was no strong evidence to favour either anticholinergic drugs or the comparators.

AUTHORS' CONCLUSIONS

Many of the drugs considered in trials in this review are no longer used in clinical practice (and this includes the most commonly tested - flavoxate). There is inadequate evidence as to determine whether any of the available drugs are better or worse than anticholinergic medications. Larger randomised controlled trials in clinical settings are required to further establish the role of these medications in the management of overactive bladder syndrome.

The challenge of overactive bladder therapy: alternative to antimuscarinic agents

Contemporary, the management of overactive bladder (OAB), a medical condition characterized by urgency, with or without urge urinary incontinence, frequency and nocturia, in absence of genitourinary pathologies or metabolic factors that could explain these symptoms, is complex, and a wide range of conservative treatments has been offered, including bladder training, biofeedback, behavioral changes, oral or intravesical anticholinergic agents, S3 sacral neuromodulation and peripheral electrical stimulation. Clinical efficacy of these treatments remains an open issue and several experimental and clinical studies were carried out in the last years improving the results of medical treatment. Here we review the pathophysiology of micturition reflex, the current therapies for OAB and the rationale for alternative treatments. Furthermore we critically address the potential use of medications targeting the central nervous system (CNS) and the primary sensory nerves of the bladder wall, we review the use of agonists of nociceptin/orphanin protein (NOP) receptor and finally we report the results obtained by intradetrusor injection of botulinum toxin.

Anticholinergic drugs versus other medications for overactive bladder syndrome in adults

BACKGROUND

Overactive bladder syndrome is defined as "urgency with or without urge incontinence, usually with frequency and nocturia". It is a common condition with significant economic and quality of life implications. While the condition's pathophysiology remains to be fully elucidated, pharmacotherapy is the main treatment option. Despite uncertainty as to drug treatment of choice, anticholinergics are increasingly being used in primary and secondary care settings. This review compares anticholinergic drugs with other types or classes of drugs for treating overactive bladder syndromes.

OBJECTIVES

To compare anticholinergic drugs with other types or classes of drugs for treating overactive bladder symptoms.

SEARCH STRATEGY

We searched the Cochrane Incontinence Group Specialised Trials Register (searched 20 December 2006) and the reference lists of relevant articles. No language or other limits were imposed.

SELECTION CRITERIA

All randomised and quasi-randomised controlled trials comparing anticholinergic drugs with other drugs for the treatment of overactive bladder symptoms. At least one arm of the study used an anticholinergic drug and at least one other arm used a non-anticholinergic drug.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed the identified studies for eligibility and methodological quality and independently extracted data from the included studies. Data analysis was performed using RevMan software (version 4.2.8).

MAIN RESULTS

Thirteen trials were included in the review. There were eight crossover trials and five parallel group studies. For the comparisons between anticholinergic drugs with tricyclic antidepressants, alpha adrenergic agonists, afferent nerve inhibitors, and calcium channel blocker a single trial was identified for each. Ten trials compared flavoxate with anticholinergics. There was no evidence of a difference in cure rates between anticholinergics and flavoxate. Adverse effects were more frequent in anticholinergic groups versus flavoxate groups (RR 2.28 95% CI 1.45 to 3.56). There was no strong evidence to favour either anticholinergic drugs or the comparators.

AUTHORS' CONCLUSIONS

Many of the drugs considered in trials in this review are no longer used in clinical practice (and this includes the most commonly tested - flavoxate). There is inadequate no evidence as to whether any of the available is better or worse than anticholinergic medications. Larger randomised controlled trials in clinical settings are required to further establish the role of these other medications in the management of overactive bladder syndrome.

Bladder sensory desensitization decreases urinary urgency

Background

Bladder desensitization has been investigated as an alternative treatment for refractory detrusor overactivity. Most open and controlled clinical trials conducted with intravesical RTX showed that desensitization delays the appearance of involuntary detrusor contractions during bladder filling and decreases the number of episodes of urgency incontinence.

Urgency is being recognised as the fundamental symptom of overactive bladder (OAB), a symptomatic complex which recent epidemiological studies have shown to affect more than 10% of the Western population. As anti-muscarinic drugs, the first line treatment for OAB, are far from being able to fully control urgency, the opportunity to test other therapeutic approaches is created. The present work was, therefore, designed as an exploratory investigation to evaluate the effect of bladder desensitization on urinary urgency.

Methods

Twenty-three OAB patients with refractory urgency entered, after given informed consent, a 30 days run-in period in which medications influencing the bladder function were interrupted. At the end of this period patients filled a seven-day voiding chart where they scored, using a 0–4 scale, the bladder sensations felt before each voiding. Then, patients were instilled with 100 ml of 10% ethanol in saline (vehicle solution) and 30 days later a second seven-day voiding chart was collected. Finally, patients were instilled with 100 ml of 50 nM RTX in 10% ethanol in saline. At 1 and 3 months additional voiding charts were collected.

At the end of the vehicle and 3 months period patients were asked to give their subjective impression about the outcome of the treatment and about the willingness to repeat the previous instillation.

Results

At the end of the run-in period the mean number of episodes of urgency per week was 71 ± 12 (mean ± SEM). After vehicle instillation, the mean number of episodes of urgency was 56 ± 11, but only 4 patients (17%) considered that their urinary condition had improved enough to repeat the treatment. At 1 and 3 months after RTX the number of episodes of urgency decreased to 39 ± 9 (p = 0.002) and 37 ± 6 (p = 0.02), respectively (p indicates statistical differences against vehicle). The percentage of patients with subjective improvement after RTX and willing to repeat the instillation at a later occasion was 69%.

Conclusion

In OAB patients with refractory urgency bladder desensitization should be further investigated as an alternative to the standard management. Additionally, the specific effect of RTX on TRPV1 receptors suggests that urothelium and sub-urothelial C-fibers play an important role to the generation of urgency sensation.

Intravesical resiniferatoxin for the treatment of women with idiopathic detrusor overactivity and urgency incontinence: A single dose, 4 weeks, double-blind, randomized, placebo controlled trial

AIMS

To assess the hypothesis that resiniferatoxin (RTX) can be useful in women with urgency incontinence and idiopathic detrusor overactivity (IDO), we conducted a prospective, double-blind, randomized, placebo-controlled, parallel trial comparing the effects of RTX and placebo.

MATERIALS AND METHODS

Fifty-eight patients were randomly assigned to receive a single intravesical dose of 100 ml of either RTX 50 nM or placebo. Safety and efficacy were evaluated over 4 weeks. The primary efficacy endpoints were voiding symptoms evaluated through the voiding diary. Secondary efficacy endpoint was urodynamic response. Quality of life was measured by the Kings' Health Questionnaire

RESULTS

Although improving trends were seen in both groups after the instillations, no statistically significant differences were found between the groups in any of the clinical or urodynamic parameters. RTX instillations were well tolerated with few and self-limited side-effects.

CONCLUSION

A single 50 nM intravesical dose of RTX was not better than placebo for the treatment of women with IDO and urgency incontinence.

Refractory neurogenic detrusor overactivity

Refractory neurogenic detrusor overactivity refers to the clinical condition that is no longer manageable by anticholinergic therapy. This condition represents a formidable task to caregivers because the treatment of urinary incontinence and adequate protection of the upper urinary tract become extremely difficult. Treatment options for refractory neurogenic detrusor overactivity include detrusor injections of botulinum toxin and intravesical instillation of vanilloid compounds, mainly resiniferatoxin, or anticholinergic drugs. If these options fail, bladder augmentation or sacral anterior root stimulation offers excellent outcomes, although at much higher costs and risks to the patients.

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.

Urodynamic effect of intravesical resiniferatoxin in patients with neurogenic detrusor overactivity of spinal origin: results of a double-blind randomized placebo-controlled trial

OBJECTIVES

To access by a placebo-controlled randomized clinical trial the effect of intravesical resiniferatoxin on the urodynamic parameters of patients with neurogenic detrusor overactivity (NDO) of spinal origin.

METHODS

Twenty eight patients with spinal NDO were randomised to receive intravesically 50 nM resiniferatoxin dissolved in 10% ethanol in saline (RTX group) or only the vehicle solution (placebo group). Filling cystometries were obtained in each patient at 1 month and 1 week before and at 1 and 3 months after treatment. In a visual analog scale patients were asked to estimate the discomfort induced by treatment. Patients were also persuaded to fill a micturition chart during the 3 days preceding each cystometry.

RESULTS

The RTX and placebo groups were homogeneous in what respects the volume to first involuntary detrusor contraction (FDC, 143+/-95 ml and 115+/-58 ml, respectively, p=0.3) and maximal cystometric capacity (MCC, 189+/-99 ml and 198+/-111 ml, respectively, p=0.8). At the end of the study, mean FDC and MCC in the RTX group, 184+/-93 ml and 314+/-135 ml, respectively were significantly higher than in the placebo group, 115+/-61 ml (p=0.03) and 204+/-92 ml (p=0.02). In the visual analogue scale discomfort caused by treatment was similar. Only 10 patients in the RTX group and 6 patients in the placebo group completed adequately the micturition chart. Mean frequency and urinary incontinence decreased significantly only in the RTX group.

CONCLUSIONS

Intravesical RTX is effective in increasing bladder capacity in spinal NDO patients. Such increment might contribute to decrease urinary frequency and incontinence of these patients.

TRPV1 (vanilloid receptor) in the urinary tract: expression, function and clinical applications

The transient receptor potential vanilloid subfamily 1 (TRPV1) is an ion channel activated by capsaicin, heat, protons and endogenous ligands such as anandamide. It is largely expressed in the urinary tract of mammals. Structures in which the receptor expression is firmly established include sensory fibers and urothelial cells, although the presence of TRPV1 in other cell types has been reported. As in other systems, pain perception was the first role attributed to TRPV1 in the urinary tract. However, it is now increasingly clear that TRPV1 also regulates the frequency of bladder reflex contractions, either through direct excitation of sensory fibers or through urothelial-sensory fiber cross talk involving the release of neuromediators from the epithelial cells. In addition, the recent identification of the receptor in urothelial and prostatic cancer cells raise the exciting hypothesis that TRPV1 is involved in cell differentiation. Desensitization of the receptor by capsaicin and resiniferatoxin has been investigated for therapeutic purposes. For the moment, lower urinary tract dysfunctions in which some benefit was obtained include painful bladder syndrome and overactive bladder of neurogenic and non-neurogenic origin. However, desensitization may become obsolete when non-toxic, potent TRPV1 antagonists become available.

Integrated control of lower urinary tract--clinical perspective

The neural mechanisms that determine social bladder control are reviewed, with a particular emphasis on the role played by sensation in the process. Much has been learnt about the neural control of the bladder from studying patients with neurological disease and those disorders that are known to disrupt bladder storage are described. Possible approaches to treatment of the resulting incontinence are reviewed and it is acknowledged that in the future, the optimal treatment for incontinence may be determined by its precise underlying pathophysiology in each instance, for example, suprapontine causes requiring different medication to spinal causes. Although the main emphasis of urological research and development so far has been the treatment of incontinence, effective therapy for other bladder disorders such an impaired emptying or bladder pain could have an important impact on the bladder symptoms of many patients.

Sacral neuromodulation in lower urinary tract dysfunction

Vesico-urethral dysfunction is a major problem in daily medical practice due to its psychological disturbances, its social costs and its high impact on quality of life. Recently, sacral neuromodulation, namely the electrical stimulation of the sacral nerves, appears to have become an alternative for radical bladder surgery particularly in cases of idiopathic bladder overactivity. The mechanism of action is only partially understood but it seems to involve a modulation in the spinal cord due to stimulation of inhibitory interneurons. Temporary sacral nerve stimulation is the first step. It comprises the temporary application of neuromodulation as a diagnostic test to determine the best location for the implant and to control the integrity of the sacral root. If test stimulation is successful, a permanent device is implanted. This procedure is safe in experienced hands. So-called idiopathic bladder overactivity still the major indication for this technique. Patients not likely to benefit from the procedure were those with complete or almost complete spinal lesions, but incomplete spinal lesions seemed to be a potential indication. This technique is now also indicated in the case of idiopathic chronic retention and chronic pelvic pain syndrome. When selection is performed, more than three-quarters of the patients showed a clinically significant response with 50% or more reduction in the frequency of incontinent episodes, but the results vary according to the author's mode of evaluation. From the economic point of view, the initial investment in the device is amortized in the mid-term by savings related to lower urinary tract dysfunction. Finally, this technique requires an attentive follow-up and adjustments to the electric parameters so as to optimize the equilibrium between the neurological systems.

Recent developments in transient receptor potential vanilloid receptor 1 agonist-based therapies

Capsaicin and other naturally occurring pungent molecules have been used for centuries as topical analgesics and rubefactants to treat a variety of chronically painful conditions. Recently, instillations of high-concentration capsaicin and resiniferatoxin solutions have been found to be useful for the management of persistent bladder pain or overactive bladder. However, only within the last 7 years has it been appreciated that the selective action of these compounds on a subset of sensory nerve fibres is mediated by agonist activity at a ligand-gated ion channel called the transient receptor potential vanilloid receptor 1 (TRPV1). Accordingly, this discovery has fueled intensive research and drug development efforts, mainly in a search for novel analgesic or anti-inflammatory therapies. Two different, but non-mutually exclusive, strategies are being pursued: optimisation of TRPV1 agonist-based therapies, which can functionally inactivate nociceptive nerve fibres, and identification of receptor antagonists, which would prevent nociceptive fibres from being activated by ongoing inflammatory stimuli. Available information on TRPV1 agonists in development and their biological rationale will be summarised in this review.

Botulinum Toxin Type A Injections for Treating Neurogenic Detrusor Overactivity Combined With Low-Compliance Bladder in Patients With Spinal Cord Lesions

OBJECTIVE

To evaluate botulinum toxin type A (BTX-A) for treating neurogenic detrusor overactivity in patients with spinal cord lesions, including those with abnormally low bladder compliance.

DESIGN

Nonrandomized, before-after trial (9-mo follow-up).

SETTING

Hospitalized care.

PARTICIPANTS

Ten patients with high detrusor contraction pressure and/or poor response to oxyphencyclimine with incontinence selected as a consecutive sample.

INTERVENTION

BTX-A (Botox; 300U) was injected into the detrusor muscle.

MAIN OUTCOME MEASURES

Urinary continence, functional bladder capacity, bladder compliance, detrusor contraction pressure, and volume at first reflex voiding. Measurements were taken before and 6, 16, and 36 weeks posttreatment.

RESULTS

Six weeks after treatment, complete continence was restored in 7 patients without oxyphencyclimine. Mean functional bladder capacity (P=.008), compliance (P=.012), and reflex volume (P=.045) significantly increased, whereas maximal detrusor contraction pressure significantly decreased (P<.001). Urodynamic variables remained significantly improved at 16 weeks, but values were returning toward baseline levels by 36 weeks. The procedure was generally uneventful, without any serious side effects.

CONCLUSIONS

BTX-A injections are an effective, well-tolerated treatment for neurogenic detrusor overactivity in patients with spinal cord lesions, even in patients with abnormally low bladder compliance. Patients may require repeat injections after 16 weeks to remain continent.

Newer pharmacologic options in management of overactive bladder syndrome

PURPOSE OF REVIEW

Urinary incontinence is an under-reported epidemic that currently affects an estimated 13 million people in the United States, of whom about 11 million are women, according to the National Institute of Diabetes and Digestive and Kidney Diseases (Publication No. 02-4132). Because many patients are unaware of curative options and perceive it to be an inevitable outcome of advancing age, they fail to report their symptoms and increase their risk of developing associated co-morbid disease. Failure to diagnose and treat this condition increases financial burdens on individuals, their families and health care organizations.

RECENT FINDINGS

Pharmacologic therapy of urge incontinence previously had limited treatment success because efficacious drugs were poorly tolerated, resulting in low patient compliance. Tolerance and effectiveness continue to be improved due to innovative new drugs and alternative delivery systems.

SUMMARY

The goal of this review is to update the clinician on the efficacy and the tolerability of established and investigational pharmacologic modalities of therapy.

Activation of transient receptor potential vanilloid 1 (TRPV1) by resiniferatoxin

Transient receptor potential vanilloid 1 (TRPV1) is a Ca(2+) permeable non-selective cation channel activated by physical and chemical stimuli. Resiniferatoxin (RTX), an ultrapotent agonist of TRPV1, is under investigation for treatment of urinary bladder hyper-reflexia and chronic pain conditions. Here, we have determined the characteristics of RTX-induced responses in cells expressing native and cloned rat TRPV1. Whole-cell currents increase with repeated application of submaximal concentrations of RTX until a maximal response is attained and do not deactivate even after prolonged washout. Interestingly, the rate of activation and block by capsazepine of RTX-induced currents are significantly slower than for capsaicin-induced currents. RTX-induced whole-cell currents are outwardly rectifying, but to a lesser extent than capsaicin-induced currents. RTX-induced single channel currents exhibit multiple conductance states and outward rectification. The open probability (P(o)) of RTX-induced currents is higher at all potentials as compared to capsaicin-induced currents, which showed a strong voltage-dependent decrease at negative potentials. Single-channel kinetic analyses reveal that open-time distribution of RTX-induced currents can be fitted with three exponential components at negative and positive potentials. The areas of distribution of the longer open time constants are significantly larger than capsaicin-induced currents. The closed-time distribution of RTX-induced currents can be fitted with three exponential components as compared to capsaicin-induced currents, which require four exponential components. Current-clamp experiments reveal that low concentrations of RTX caused a slow and sustained depolarization beyond threshold while generating few action potentials. Concentrations of capsaicin required for the same extent of depolarization generated a significantly greater number of action potentials. These properties of RTX may play a role in its clinical usefulness.

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

OBJECTIVE

To examine the effectiveness and tolerability of multiple intravesical instillations of 10 nmol/L resiniferatoxin in patients with detrusor overactivity (DO) refractory to anticholinergic agents, as not all these patients are successfully treated by one such instillation.

PATIENTS AND METHODS

The study included 53 patients with DO from neurogenic (NDO, 10), previous bladder outlet obstruction (BOO, 20) or idiopathic cause (IDO, 23) and who were refractory to anticholinergic agents. Patients received three to four instillations of 10 nmol/L resiniferatoxin, as outpatients. The International Prostate Symptom Score and quality-of-life index were recorded, and a video-urodynamic study conducted at baseline and 3 months after treatment. The therapeutic results and urodynamic variables were compared among patients with different causes of DO.

RESULTS

Four patients withdrew from the study after the first instillation because of urinary tract infection or severe pain on urination, leaving 49 who completed at least three instillations. The overall results were an excellent response in 17 patients (35%), improvement in 13 (27%) and failure in 19 (39%); the treatment was deemed a success (excellent or improved) in 16 of 20 with previous BOO, 11 of 19 with IDO, and only three of 10 with NDO (P = 0.011). Patients had significant improvements in the storage symptom score, total symptom score and quality-of-life index after treatment. The cystometric capacity and the postvoid residual were significantly greater and voiding efficiency significantly less after treatment. DO during the urodynamic study was absent in 12 patients after treatment.

CONCLUSIONS

Multiple intravesical instillations of 10 nmol/L resiniferatoxin are effective in treating patients with DO refractory to anticholinergics.

Bladder C-Fiber Desensitization Induces a Long-Lasting Improvement of BPH-Associated Storage LUTS: A Pilot Study

OBJECTIVES

To evaluate the effect of bladder C-fiber desensitization on BPH-associated storage LUTS.

METHODS

Twelve patients with predominant BPH-associated storage LUTS gave written informed consent to enter the study. IPSS and QoL scores, micturition chart, uroflowmetry, cystometry and post-void residual (PVR) were obtained at baseline and at 1, 3 and 6 months after a single intravesical administration of 50 nM resiniferatoxin (RTX) solution.

RESULTS

Mean IPSS score decreased from 20.1 +/- 6.0 to 10.5 +/- 4.4 at 1 month (p = 0.0001), to 10.3 +/- 4.4 at 3 months (p = 0.00001) and to 9.8 +/- 5.7 at 6 months (p < 0.00001). Mean QoL score decreased from 4.5 +/- 1 to 2.5 +/- 1 at 1 month (p = 0.0001), to 2.3 +/- 1 at 3 months (p = 0.0004) and to 2.6 +/- 1.2 at 6 months (p = 0.0003). Mean urinary frequency decreased from 15.2 +/- 8.5 to 10.8 +/- 7.3 at 1 month (p = 0.0002), to 10.2 +/- 4.9 at 3 months (p = 0.002) and to 11.7 +/- 9.2 at 6 months (p = 0.005). Urge incontinence, which was present in six cases, disappeared in 4 patients and decreased to less than half in the other two. Mean first desire to void and maximal cystometric capacity increased significantly after RTX whereas uroflowmetry and PVR were not altered.

CONCLUSIONS

Intravesical desensitization of bladder C fibres with intravesical RTX might be useful in the treatment of patients with predominant BPH associated storage LUTS.

Intravesical resiniferatoxin for patients with neurogenic detrusor overactivity

BACKGROUND

Resiniferatoxin (RTX), a substance isolated from some species of Euphobia, is a specific C-fiber neurotoxin which produces desensitization rather than excitation. At first, we performed intravesical RTX therapy on eight patients with neurogenic detrusor overactivity. After we confirmed the safety and efficacy, a Japanese RTX study group was organized and a new protocol made. The multicenter trial was performed in Japan. However, the efficacy of the treatments was different among the institutions. Therefore, we have compared the results between the first protocol and the new one at our hospital.

METHODS

The first and second protocol involved the RTX solution (30 mL of 500 nM, and 100 mL of 1 micro M, respectively) being instillated in the bladder for 30 min by almost the same procedures. Effects on bladder function were evaluated during treatment and at follow up.

RESULTS

For the first and second protocols, six out of eight patients noted symptomatic improvement while two patients did not notice any change in the degree of incontinence for one month. The mean urodynamic bladder capacity had significantly increased from 138.0 +/- 64.4 mL to 227.3 +/- 112.4 mL and 133.1 +/- 43.3 mL to 247.0 +/- 102.3 mL 1 month after RTX treatment for the first and second protocols, respectively (P < 0.05). No severe side-effects were seen in either group.

CONCLUSION

Intravesical RTX improved bladder capacity in patients with neurogenic detrusor overactivity in both protocols. The concentration of RTX did not exhibit any change in the effect and safety in our hospital. Intravesical RTX is a promising treatment for neurogenic detrusor overactivity.

Mechanisms involved in new therapies for overactive bladder

During the last few years, vanilloid substances and botulinum-A toxin were extensively investigated as new therapies for overactive bladder. Intravesical administration of capsaicin or resiniferatoxin--2 members of the vanilloid family--has been shown to increase bladder capacity and decrease urge incontinence in patients with neurogenic, as well as nonneurogenic, forms of detrusor overactivity. In addition, vanilloids have been shown also to reduce bladder pain in patients with hypersensitive disorders. Vanilloids are exogenous ligands of vanilloid receptor type 1 (VR1), an ion channel present in the membrane of type C primary afferent nerve fibers. This receptor, which plays a key role in pain perception and control of the micturition reflex, may be upregulated by nerve growth factor (NGF), a neurotrophic molecule detected in high concentrations in overactive detrusor tissue. Vanilloids, by reducing uptake of NGF through sensory neurons, may counteract VR1 upregulation. Intravesical injections of botulinum-A toxin, a neurotoxin produced by Clostridium botulinum, were shown to increase bladder capacity and to decrease urge incontinence episodes in patients with neurogenic detrusor overactivity. Botulinum-A toxin impedes the release of acetylcholine from cholinergic nerve endings at the neuromuscular junction, leading to paralysis of the detrusor smooth muscle.

Treatment options for female urinary incontinence

Contrary to the belief of some patients and physicians, urinary incontinence in women should not be accepted as a natural and inevitable part of aging. Indeed, it is a costly problem, psychologically, physically, and economically, and can have a considerable impact on a woman's quality of life. Accurate diagnosis of the type of incontinence is important to implement appropriate and successful treatment. In general, a focused medical and symptom-oriented history and physical examination is all that is needed to establish the correct diagnosis. UI, SUI, and mixed incontinence are the most common types seen in women. Most patients with urge incontinence respond to behavioral treatments, PFEs, medication, or some combination thereof. Recalcitrant cases should be referred to a specialist. Patients with SUI may respond to PFEs, but many require surgical intervention for a satisfactory outcome. The successful treatment of urinary incontinence in a woman can lead to a substantial improvement in her overall quality of life, and for the physician, can be as professionally rewarding as the successful management of various other chronic disease states.

Resiniferatoxin for detrusor instability refractory to anticholinergics

PURPOSE

We have evaluated the clinical and urodynamic effects of intravesical instillation of resiniferatoxin in patients with idiopathic detrusor instability refractory to anticholinergics.

MATERIALS AND METHODS

There were 30 women, median age 56 years old with detrusor instability for over 6 months and a history of anticholinergic use with no response or intolerable collateral effects. A 50 nM solution of resiniferatoxin was prepared for intravesical instillation. All patients were evaluated for urinary symptoms, as well as for urodynamic assessments before and 30 days after instillation. Tolerability was analyzed during the instillation.

RESULTS

A clinical improvement was observed in 30% of the patients with urinary urgency and in 33% of the patients with urge-incontinence. The mean maximum cystometric capacity before application was 303.9 +/- 78.9 and after application 341 +/- 84.6. No significant difference was observed (p = 0.585). The mean maximum amplitude of the contractions diminished from 47.86 +/- 29.64 to 38.72 +/- 30.77 (p = 0.002).

CONCLUSIONS

Resiniferatoxin, in this concentration, proved to be useful in a small percentage of patients regarding clinical detrusor instability. Maximum amplitude of the involuntary contractions was significantly reduced and in 33% patients the involuntary contractions disappeared. Further studies with different concentrations are recommended.

Intravesical capsaicin versus resiniferatoxin for the treatment of detrusor hyperreflexia in spinal cord injured patients: a double-blind, randomized, controlled study

PURPOSE

Chemical defunctionalization of C-fiber bladder afferents with intravesical vanilloids such as capsaicin (CAP) or resiniferatoxin (RTX) improves detrusor hyperreflexia in humans and animals. The little existing data comparing the efficacy and tolerance of these 2 vanilloid agents seem to favor RTX in 10% alcohol over CAP, which is usually diluted in 30% alcohol. We compared the efficacy and tolerability of the 2 vanilloid agonists in what to our knowledge is the first randomized, controlled study comparing nonalcohol CAP vs RTX in 10% alcohol in neurogenic patients with detrusor hyperreflexia.

MATERIALS AND METHODS

This single center, randomized, double-blind, parallel groups study included 39 spinal cord injured adults with detrusor hyperreflexia. On day 0 patients were randomized to receive 1, 100 ml intravesical instillation of 100 nMol/l RTX diluted in 10% ethanol or 1 mmol/l CAP diluted in glucidic solvent. Efficacy (voiding chart and cystomanometry) and tolerability were evaluated during a 3-month followup.

RESULTS

On day 30 clinical and urodynamical improvement was found in 78% and 83% of patients with CAP vs 80% and 60% with RTX, respectively, without a significant difference between the 2 treated groups. The benefit remained in two-thirds of the 2 groups on day 90. There were no significant differences in regard to the incidence, nature or duration of side effects in CAP vs RTX treated patients.

CONCLUSIONS

Our results strongly argue for the importance of accounting for the role of vanilloid solute when interpreting the efficacy and tolerance of vesical vanilloid instillation in detrusor hyperreflexia cases. They suggest that a glucidic solute is a valuable solvent for vanilloid instillation.

Future research needs for the definition/diagnosis of interstitial cystitis

In Workshop 8 at the International Conference on Interstitial Cystitis (Kyoto March 2003, future research needs for the definition/diagnosis of interstitial cystitis (IC) were discussed by the participants. To structure discussions a study proposal was used. This workshop decided that research should focus on identifying and validating classification criteria for the diagnosis of IC. This might well be done in a (multi-centre) study with a control group of urge-frequency patients without pain (OAB?). However, before doing so standards should be defined as on how to perform and interpret vaginal examination, urodynamic investigation, cystoscopy under anesthesia, potassium sensitivity test, and histopathology in these patients.

Effectiveness of intravesical resiniferatoxin in treating detrusor hyper-reflexia and external sphincter dyssynergia in patients with chronic spinal cord lesions

OBJECTIVE

To investigate the therapeutic effect of resiniferatoxin in patients with chronic spinal cord lesions, as detrusor hyper-reflexia and external sphincter dyssynergia (DESD) are common phenomenon in such patients.

PATIENTS AND METHODS

Twenty patients with chronic spinal cord lesions and DESD refractory to anticholinergic treatment were enrolled in a prospective study. They were treated with 30 mL of 10 micro mol/L resiniferatoxin for 30 min. Four types of response were recorded during instillation: type 1, a sustained high-pressure detrusor contraction followed by complete acontractility; type 2, a high-pressure contraction followed by progressively lower contractions; type 3, intermittent high-pressure detrusor contractions throughout the instillation; type 4, intermittent low-pressure detrusor contractions. The changes in clinical symptoms and urodynamics at baseline, during resiniferatoxin instillation and 1 month after treatment were compared.

RESULTS

All patients had DESD and 10 had autonomic dysreflexia; 18 had urinary incontinence and 13 had difficult urination. Continence and/or difficult urination improved in 12 patients, including all five with type 1, four with type 2, two with type 3 and only one with a type 4 response. Four patients became dry during the day and eight had less urgency and fewer incontinence episodes, and a significantly increased voided volume. Of the 13 patients who complained of difficult urination, eight had an improvement either by spontaneous voiding (five) or the Crede manoeuvre to voiding (three). The mean (sd) maximum cystometric capacity increased significantly after treatment, from 102.1 (31.5) to 236.6 (88.6) mL (P < 0.001), but the detrusor pressure showed no significant change, at 55.9 (23.2) to 47.5 (28.1) cmH2O. The external urethral sphincter showed intermittent activity during reflexic detrusor contractions at baseline.

CONCLUSION

Resiniferatoxin at 10 micro mol/L has a clinical effect on two-thirds of patients with a spinal cord lesion and detrusor hyper-reflexia, but not on the DESD. The initial response to resiniferatoxin instillation might predict a favourable therapeutic outcome.

Effectiveness of intravesical resiniferatoxin for anticholinergic treatment refractory detrusor overactivity due to nonspinal cord lesions

PURPOSE

Evidence suggests that unmyelinated C fibers become predominant in the mediation of the detrusor reflex in patients with chronic spinal cord lesions and possibly in idiopathic detrusor hyperactivity. Intravesical vanilloid therapy might be effective in treating refractory detrusor overactivity due to nonspinal cord lesion. This study investigated the clinical effect of intravesical resiniferatoxin in treating detrusor overactivity of nonspinal cord lesions refractory to anticholinergics.

MATERIALS AND METHODS

A total of 41 patients received intravesical resiniferatoxin therapy with 10 ml of 100 nM resiniferatoxin in 10% ethanol solution for 40 minutes. The clinical effects on a decrease in incontinence episodes and urodynamic study were evaluated at baseline and after treatment. Clinical improvement was considered if patients became dry or had a decrease in incontinence episodes of 50%. Therapeutic results were analyzed by disease category and type of initial detrusor response.

RESULTS

Of the 41 patients 10 had neurogenic lesions, 18 had previous transurethral prostatectomy and 13 had idiopathic detrusor overactivity. There were 20 women and 21 men with a mean age of 73.6 years (range 43 to 82) and a symptom duration of 3.6 +/- 4.5 years. After resiniferatoxin treatment 21 patients had clinical improvement (51.2%) including 5 with neurogenic (50%), 11 with previous transurethral prostatectomy (61.1%) and 5 with idiopathic detrusor overactivity (38.5%). An improvement was found in 11 patients with type I initial response (84.6%), 3 patients with type II response (23%) and 7 patients with type III response (46.7%). The 21 patients with improvement had a significant increase in cystometric capacity (208 +/- 80.7 vs 287.2 +/- 118.6 ml, p = 0.001) and a significant decrease in detrusor pressure (33.6 +/- 11.1 vs 27.4 +/- 11.8 cmH(2)O, p = 0.047), but no significant difference in maximal flow rate and residual urine volume.

CONCLUSIONS

Intravesical resiniferatoxin was effective in treating refractory detrusor overactivity in 51.2% of patients with nonspinal cord lesions. Patients with detrusor overactivity due to previous bladder outlet obstruction benefited the most. Detrusor contractility decreased after resiniferatoxin treatment in the group with improvement but did not influence voiding efficiency. The initial detrusor response to resiniferatoxin treatment might predict the clinical outcome.

Recent developments in the management of detrusor overactivity

PURPOSE OF REVIEW

Detrusor overactivity is a relatively common yet embarrassing symptom complex with significant impact on quality of life. The mainstay of current pharmacological treatment involves use of muscarinic receptor antagonists, but their therapeutic efficacy is limited by their troublesome side effects resulting in the non-continuance of treatment in a significant number of patients. Therefore, the development of new drugs can proceed by targeting alternative pathways affecting detrusor overactivity. In this article, the pharmacological basis for the current therapeutic alternatives for managing detrusor overactivity and possible future developments are discussed.

RECENT FINDINGS

It is clear that far from being a passive container for urine, the urothelium is a crucial part of the bladder. Its functions are complex, dynamic and important, and only now becoming understood. The release of ATP from urothelium in response to distension and its action on P2X receptors resulting in activating both motor and sensory neurons is being increasingly recognised. In the normal bladder, muscarinic receptor stimulation produces the main part of detrusor contraction. However, in functionally abnormal bladders, a non-cholinergic activation via the purinergic receptors may occur. The central nervous mechanisms controlling the micturition reflex have also recently attracted attention.

SUMMARY

Recent research has suggested that several transmitters may modulate voiding. However, few drugs with clinical benefits have been developed so far. Present treatments for overactive bladders have significant non-compliance rates. Hopefully, future research will lead to drugs with greater therapeutic benefits and better tolerance.

The role of capsaicin-sensitive afferents in autonomic dysreflexia in patients with spinal cord injury

OBJECTIVES

To determine whether capsaicin-sensitive nerves in the bladder form the afferent limb involved in autonomic dysreflexia (AD) in patients with spinal cord injury (SCI).

PATIENTS AND METHODS

Seven men with SCI (five cervical cord, two thoracic cord) with AD and detrusor hyper-reflexia (DH) were enrolled. Under general anaesthesia, capsaicin solution (100 mL of 2 mmol/L in 10% ethanol) was instilled in the bladder and retained for 30 min. The patients were assessed by medium-fill cystometry (CMG) just before and 50 min after the capsaicin treatment. Intra-arterial blood pressure (BP) and heart rate were monitored continuously throughout the procedure; 10% ethanol was instilled before capsaicin treatment in four patients as a control. Serum catecholamines were measured during bladder filling and capsaicin treatment, and the blood ethanol concentration also measured after instillation in all patients. The CMG with concomitant monitoring of BP and heart rate was repeated 1 week, 1, 3, 6, 12 and 24 months after instillation. In two patients the instillations were repeated 5 and 12 months after the first because of recurrence of DH. Urodynamic variables assessed were maximum cystometric capacity (MCC), maximum amplitude of uninhibited detrusor contraction (UICmax), the bladder capacity at 40 cmH2O detrusor pressure (Cdp40) and a systolic BP of> 140 mmHg or diastolic BP of> 90 mmHg (C(HT)).

RESULTS

There was an increase in BP and a decrease in heart rate in all patients during bladder filling before capsaicin treatment. Instillation of capsaicin produced a significant increase in both systolic and diastolic BP and a significant decrease in heart rate. The maximum cardiovascular effects were at 5-10 min after instillation and gradually returned to baseline within 40 min. The vehicle had negligible effects on either BP or heart rate. After capsaicin treatment, the responses of BP and heart rate to bladder distension were significantly reduced. Both serum catecholamine values and the blood ethanol concentration remained within normal limits. The mean (range) follow-up after the first treatment was 15 (6-30) months. One month after treatment all seven patients became continent and their episodes of AD became negligible and well tolerable between catheterizations (for 3-4 h); the effects lasted for >or= 3 months in all. MCC was significantly increased at 4 weeks and 3 months, and UICmax significantly decreased at 4 weeks after treatment. Both mean Cdp40 and C(HT) increased 1 week, 1 and 3 months after treatment. Two patients received a second instillation, and have been continent with no symptomatic AD for 6 and 24 months. The remaining five patients have been continent with no symptomatic AD for 6-12 months.

CONCLUSION

These results indicate that intravesical capsaicin, but not the vehicle, acutely triggers AD in patients with SCI, suggesting involvement of bladder capsaicin- sensitive afferents in AD in these patients. The results also suggest that intravesical capsaicin may be a promising therapy for both AD and DH in such patients. Further long-term follow-up studies are needed to evaluate the duration of its effect.

Neurogenic inflammation of the bladder

Current evidence suggests multiple and redundant pathways through which the nervous system can initiate, amplify, and perpetuate inflammation. Many of the processes initiated by neurogenic inflammation have the capacity to recruit the participation of additional sensory nerves. These observations indicate that effective strategies for prevention or treatment of neurogenic inflammation of the bladder will entail or require intervention at multiple points. It has been observed that pain management in the future will be based on selective intervention tailored to the specific processes modulating pain perception in individual patients. It is exciting to contemplate the same approach to prevention and treatment of neurogenic bladder inflammation.

Intra-ureteric capsaicin in loin pain haematuria syndrome: efficacy and complications

OBJECTIVE

To evaluate the safety and efficacy of intra-ureteric capsaicin for loin pain haematuria syndrome (LPHS).

PATIENTS AND METHODS

In an open prospective pilot study, four middle-aged patients (three women and one man) with LPHS resistant to therapies such as splanchnic nerve block, psychological treatment or renal autotransplantation (one) were assessed. An intra-ureteric infusion of capsaicin (30 mg/100 mL of 30% alcohol in saline) for 30 min with bladder irrigation was administered under general anaesthesia, with a subsequent intravenous patient-controlled narcotic analgesic pump for pain control. Double-concentration capsaicin was used for second infusions, if necessary when the response to the earlier infusion was inadequate or incomplete.

RESULTS

The first patient had experienced reduced pain levels for the first 3 months only, with no benefit from the subsequent treatments with higher doses of capsaicin (60 mg). The second patient with recurrent pain in an autotransplanted kidney had no benefit from either a 30 or 60 mg capsaicin infusion a month apart, but developed a fibrotic stricture at the transplant pelvi-ureteric junction, requiring pyelocystoplasty. The third patient with concurrent depression had no benefit from a 30-mg infusion of capsaicin. The fourth patient experienced no pain relief from a 30 mg infusion of capsaicin but developed proteinuria secondary to mesangial proliferative glomerulonephritis, ureteric inflammation needing stenting within 7 days of treatment and subsequently nephrectomy for a nonfunctioning kidney at 3 months.

CONCLUSION

Intra-ureteric capsaicin was neither effective nor safe in LPHS; the contribution of the alcohol diluent cannot be excluded.

The effect of intravesical resiniferatoxin in patients with idiopathic detrusor instability suggests that involuntary detrusor contractions are triggered by C-fiber input

PURPOSE

We evaluated the role of bladder C-fiber input in involuntary detrusor activity in patients with idiopathic detrusor instability.

MATERIALS AND METHODS

Filling cystometry and a voiding chart were done in 13 patients with idiopathic detrusor instability. The first detrusor contraction, maximal cystometric capacity, daily frequency and the number of episodes of urinary incontinence were determined. A 50 nM. solution of resiniferatoxin, a specific C-fiber neurotoxin, was then instilled in the bladder for 30 minutes. Patients were reevaluated 30 and 90 days later.

RESULTS

Resiniferatoxin instillation delayed or suppressed involuntary detrusor contractions during filling cystometry. The mean first detrusor contraction plus or minus standard deviation increased from 170 +/- 109 ml. at baseline to 440 +/- 130 ml. (p = 0.0001) at 30 days and to 391 +/- 165 ml. (p = 0.008) at 90 days. Mean maximal cystometric capacity increased from 291 +/- 160 to 472 +/- 139 ml. (p = 0.01) at 30 days and to 413 +/- 153 ml. (p = 0.1) at 90 days. The mean number of episodes of urinary incontinence daily decreased from 4.3 +/- 2.7 to 0.9 +/- 2.7 (p = 0.001) at 30 days and to 0.7 +/- 0.9 (p = 0.009) at 90 days. Mean frequency daily also decreased from 12 +/- 3.2 to 9.7 +/- 3.2 (p = 0.003) and to 9.9 +/- 3.5 (p = 0.001) times at the same time points, respectively.

CONCLUSIONS

C-fiber input seems to have an important role in the generation of involuntary detrusor contractions and lower urinary tract symptoms in patients with idiopathic detrusor instability. Substances that block C-fiber input may represent a new strategy for treating this bladder dysfunction.

Vanilloid (capsaicin) receptors in health and disease

The cloned vanilloid (capsaicin) receptor subtype 1 (VR1) integrates multiple noxious stimuli on peripheral terminals of primary sensory neurons. The initial excitation of these neurons is followed by a lasting refractory state, traditionally termed desensitization, that has clear therapeutic potential. Capsaicin is used to relieve neuropathic pain, uremic pruritus, and bladder overactivity. The ultrapotent vanilloid resiniferatoxin, now in phase 2 clinical trials, has improved tolerability. A less recognized human exposure to high capsaicin concentrations may occur by pepper sprays used in law enforcement. Evidence is mounting that VR1 expression is not restricted to sensory neurons. From the olfactory bulb to the cerebellum, VR1-expressing neurons are present in a number of brain nuclei, where they might be activated by anandamide. VR1 presence also was demonstrated in nonneuronal tissues. These discoveries place VR1 in a much broader perspective than pain perception and enhance the potential for unforeseen side effects, especially following prolonged vanilloid therapy. The expression of VR1 is plastic and down-regulated during vanilloid therapy, which might have a pivotal role in desensitization. Good evidence suggests altered VR1 expression in various disease states. This recognition not only may provide novel insights into pathogenesis but also may prove useful in diagnosis.

Vanilloid receptor and detrusor instability

Very recently, a membrane receptor (vanilloid receptor type 1 [VR-1]) sensitive to capsaicin or resiniferatoxin (RTX) was identified in small- and medium-sized dorsal root ganglion neurons that give rise to most unmyelinated sensory fibers. After vanilloid binding to VR-1, these neurons remain transiently desensitized; that is, less reactive to natural stimuli. It is this effect of vanilloid substances that is being investigated for its potential therapeutic utility. In the urinary bladder, VR-1-expressing fibers are extremely abundant in the mucosa and in the muscular layer. In the latter, VR-1 fibers are intimately apposed to smooth muscle cells. The demonstration, several years ago, that these fibers were involved in detrusor hyperreflexia of spinal origin and in bladder pain processing, justified the clinical application of intravesical capsaicin or RTX in humans with these bladder diseases. More recently, the experimental and clinical evidence that the same type of bladder sensory fibers were also involved in detrusor instability made a strong case for intravesical RTX assay in patients with idiopathic detrusor instability.

Vanilloid receptor ligands: hopes and realities for the future

Neurons possessing C-fibers transmit nociceptive information into the central nervous system and participate in various reflex responses. These neurons carry receptors that bind capsaicin, recently identified as the vanilloid VR1 receptor. Excitation of these cells by capsaicin is followed by a lasting refractory state, termed desensitisation, in which the neurons fail to respond to a variety of noxious stimuli. Desensitisation to capsaicin has a clear therapeutic potential in relieving neuropathic pain and ameliorating urinary bladder overactivity, just to cite 2 important examples. Vanilloids may also be beneficial in the treatment of benign prostate hyperplasia (BPH). Since the majority of elderly patients have neuropathic pain co-existent with urinary incontinence and/or BPH, a drug that ameliorates pain and improves urinary symptoms at the same time promises to be of great clinical value in geriatric medicine. In fact, capsaicin has already been shown to have a role in the treatment of conditions that can arise in the elderly, including herpes zoster-related neuropathic pain, diabetic neuropathy, postmastectomy pain, uraemic itching associated with renal failure, and urinary incontinence. The potent VR1 agonist resiniferatoxin, now in phase II clinical trials, appears to be superior to capsaicin in terms of its tolerability profile. Recent discoveries enhance the therapeutic potential of vanilloids. The recognition that VR1 also functions as a principal receptor for protons and eicosanoids implies that VR1 antagonists may be of value in the treatment of inflammatory hyperalgesia and pain. Animal experimentation has already lent support to this assumption. The discovery of VR1-expressing cells in the brain as well as in non-neural tissues such as the kidney and urothelium places VR1 in a much broader perspective than peripheral pain perception, and is hoped to identify further, yet unsuspected, indications for vanilloid therapy. The realisation that VR1 and cannabinoid CB1 receptors have overlapping ligand recognition properties may also have far-reaching implications for vanilloid therapy. In fact, arvanil, a combined agonist of VR1 and CB1 receptors, has already proved to be a powerful analgesic drug in the mouse. From academic molecular biology laboratories to industrial drug discovery centres to the clinics, there is a steady flow of new data, forcing us to constantly revise the ways we are thinking about vanilloid receptor ligands and their hopes and realities for the future. This review covers the most promising current trends in vanilloid research with special emphasis on geriatric medicine.

Urodynamic and clinical evidence of acute inhibitory effects of intravesical nociceptin/orphanin FQ on detrusor overactivity in humans: a pilot study

PURPOSE

Management of neurogenic incontinence is complex and available treatments are not satisfactory. Nociceptin/orphanin FQ, a recently discovered neuropeptide, has been reported to inhibit the voiding reflex in the rat. These experimental results prompted us to investigate the urodynamic and clinical effects of intravesical instillation of nociceptin/orphanin FQ in humans.

MATERIAL AND METHODS

Our study involved 5 normal subjects (group 1) with a mean age of 40.4 years (range 21 to 54) and 9 patients (group 2) 40.4 years (24 to 54). All patients in group 2 presented with detrusor hyperreflexia refractory to standard therapy. They were invited to undergo a filling cystometrogram with saline solution and after 30 minutes, a new one with a solution containing 1 microM. nociceptin/orphanin FQ. The urodynamic parameters that were recorded included bladder capacity, volume threshold for the appearance of detrusor hyperreflexia and maximum bladder pressure. Clinical and urodynamic followup was performed after 15 days. The data were statistically analyzed with 1-way analysis of variance followed by the Dunnett test for multiple comparison considered statistically significant with p <0.05.

RESULTS

Intravesical instillation of 1 microM. nociceptin/orphanin FQ in group 1 did not produce significant functional changes. This infusion in group 2 produced a statistically significant increase in mean bladder capacity and volume threshold for the appearance of detrusor hyperreflexia from 164 plus or minus standard deviation (SD) 84 to 301 +/- 118 and 93 plus or minus SD 41 to 231 +/- 104 ml. (p <0.05, respectively). Mean maximum bladder pressure decreased from 79 plus or minus SD 25 to 54 +/- 44 cm. water but was not statistically significant (p = 0.19). After 15 days an absence of clinical improvement was noticed in group 2, and the urodynamic control did not show any significant changes compared to the values before nociceptin/orphanin FQ treatment. No severe symptomatic reactions were observed during infusion of 1 microM. nociceptin/orphanin FQ.

CONCLUSIONS

Our results demonstrate that nociceptin/orphanin FQ is able to elicit a robust inhibitory effect on voiding reflex in group 2 but not 1. The ideal dosage, route of administration of nociceptin/orphanin FQ and treatment interval are not yet established.