Intravesical Capsaicin for Treatment of Severe Bladder Pain: A Randomized Placebo Controlled Study

Mechanotransduction in the urothelium: ATP signalling and mechanoreceptors

The urothelium, which covers the inner surface of the bladder, is continuously exposed to a complex physical environment where it is stimulated by, and responds to, a wide range of mechanical cues. Mechanically activated ion channels endow the urothelium with functioning in the conversion of mechanical stimuli into biochemical events that influence the surface of the urothelium itself as well as suburothelial tissues, including afferent nerve fibres, interstitial cells of Cajal and detrusor smooth muscle cells, to ensure normal urinary function during the cycle of filling and voiding. However, under prolonged and abnormal loading conditions, the urothelial sensory system can become maladaptive, leading to the development of bladder dysfunction. In this review, we summarize developments in the understanding of urothelial mechanotransduction from two perspectives: first, with regard to the functions of urothelial mechanotransduction, particularly stretch-mediated ATP signalling and the regulation of urothelial surface area; and secondly, with regard to the mechanoreceptors present in the urothelium, primarily transient receptor potential channels and mechanosensitive Piezo channels, and the potential pathophysiological role of these channels in the bladder. A more thorough understanding of urothelial mechanotransduction function may inspire the development of new therapeutic strategies for lower urinary tract diseases.

Herbal Medicine for Pain Management: Efficacy and Drug Interactions

Complementary and alternative medicines such as herbal medicines are not currently part of the conventional medical system. As the popularity of and global market for herbal medicine grows among all age groups, with supporting scientific data and clinical trials, specific alternative treatments such as herbal medicine can be reclassified as a practice of conventional medicine. One of the most common conditions for which adults use herbal medicine is pain. However, herbal medicines carry safety concerns and may impact the efficacy of conventional therapies. Unfortunately, mechanisms of action are poorly understood, and their use is unregulated and often underreported to medical professionals. This review aims to compile common and available herbal medicines which can be used as an alternative to or in combination with conventional pain management approaches. Efficacy and safety are assessed through clinical studies on pain relief. Ensuing herb–drug interactions such as cytochrome modulation, additive and synergistic effects, and contraindications are discussed. While self-management has been recognized as part of the overall treatment strategy for patients suffering from chronic pain, it is important for practitioners to be able to also optimize and integrate herbal medicine and, if warranted, other complementary and alternative medicines into their care.

Local drug delivery systems for inflammatory diseases: Status quo, challenges, and opportunities

Inflammation that is not resolved in due course becomes a chronic disease. The treatment of chronic inflammatory diseases involves a long-term use of anti-inflammatory drugs such as corticosteroids and nonsteroidal anti-inflammatory drugs, often accompanied by dose-dependent side effects. Local drug delivery systems have been widely explored to reduce their off-target side effects and the medication frequency, with several products making to the market or in development over the years. However, numerous challenges remain, and drug delivery technology is underutilized in some applications. This review showcases local drug delivery systems in different inflammatory diseases, including the targets well-known to drug delivery scientists (e.g., joints, eyes, and teeth) and other applications with untapped opportunities (e.g., sinus, bladder, and colon). In each section, we start with a brief description of the disease and commonly used therapy, introduce local drug delivery systems currently on the market or in the development stage, focusing on polymeric systems, and discuss the remaining challenges and opportunities in future product development.

Suppression of adenosine A2a receptors alleviates bladder overactivity and hyperalgesia in cyclophosphamide-induced cystitis by inhibiting TRPV1

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a type of chronic bladder inflammation characterized by increased voiding frequency, urgency and pelvic pain. The sensitization of bladder afferents is widely regarded as one of the pathophysiological changes in the development of IC/BPS. There is evidence that adenosine A_2a receptors are involved in regulating the sensitization of sensory afferents. However, the effect of adenosine A_2a receptors on cystitis remains unknown. In the present study, a rat model of chronic cystitis was established by intraperitoneal injection with cyclophosphamide (CYP). Cystometry and behavioral tests were performed to investigate bladder micturition function and nociceptive pain. The rats with chronic cystitis showed symptoms of bladder overactivity, characterized by an increase in bladder voiding frequency and voiding pressure. CYP treatment significantly increased the expression of the A_2a receptor in bladder afferent fibers and dorsal root ganglion (DRG) neurons. The A_2a receptor antagonist ZM241385 prevented bladder overactivity and hyperalgesia elicited by CYP-induced cystitis. In addition, the A_2a receptor and TRPV1 were coexpressed on DRG neurons. The TRPV1 antagonist capsazepine blocked bladder overactivity induced by the A_2a receptor agonist CGS21680. In contrast, ZM241385 significantly inhibited the capsaicin-induced increase in intracellular calcium concentration in DRG neurons. These results suggest that suppression of adenosine A_2a receptors in bladder afferents alleviates bladder overactivity and hyperalgesia elicited by CYP-induced cystitis in rats by inhibiting TRPV1, indicating that the adenosine A_2a receptor in bladder afferents is a potential therapeutic target for the treatment of IC/BPS.

Interventions for treating people with symptoms of bladder pain syndrome: a network meta-analysis

BACKGROUND

Bladder pain syndrome (BPS), which includes the condition of interstitial cystitis, is a poorly understood clinical condition for which patients present with varying symptoms. Management of BPS is challenging for both patients and practitioners. At present, there is no universally accepted diagnosis and diverse causes have been proposed. This is reflected in wide-ranging treatment options, used alone or in combination, with limited evidence. A network meta-analysis (NMA) simultaneously comparing multiple treatments may help to determine the best treatment options for patients with BPS.

OBJECTIVES

To conduct a network meta-analysis to assess the effects of interventions for treating people with symptoms of bladder pain syndrome (BPS).

SEARCH METHODS

We searched the Cochrane Incontinence Specialised Register, which contains trials identified from the Cochrane Central Register of Controlled Trials (CENTRAL, in the Cochrane Library), MEDLINE, MEDLINE In-Process, MEDLINE Epub Ahead of Print, ClinicalTrials.gov, the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) and handsearched journals and conference proceedings (searched 11 May 2018) and the reference lists of relevant articles. We conducted a further search on 5 June 2019, which yielded four small studies that were screened for eligibility but were not incorporated into the review.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs of interventions for treating adults with BPS. All types of interventions (including conservative, pharmacological and surgical) were eligible.

DATA COLLECTION AND ANALYSIS

We assessed the risk of bias of included studies using Cochrane's 'Risk of bias' tool. Primary outcomes were the number of people cured or improved, pain, frequency and nocturia. For each outcome, random-effects NMA models were fitted using WinBUGS 1.4. We monitored median odds ratios (ORs) for binary outcomes and mean differences (MDs) for continuous outcomes with 95% credible intervals (Crls). We compared results of the NMA with direct evidence from pairwise meta-analysis of head-to-head trials. We used the CINeMA tool to assess the certainty of evidence for selected treatment categories.

MAIN RESULTS

We included 81 RCTs involving 4674 people with a median of 38 participants (range 10 to 369) per RCT. Most trials compared treatment against control; few trials compared two active treatments. There were 65 different active treatments, and some comparisons were informed by direct evidence from only one trial. To simplify, treatments were grouped into 31 treatment categories by mode of action. Most studies were judged to have unclear or high risk of bias for most domains, particularly for selection and detection bias. Overall, the NMA suggested that six (proportion cured/improved), one (pain), one (frequency) and zero (nocturia) treatment categories were effective compared with control, but there was great uncertainty around estimates of effect. Due to the large number of intervention comparisons in this review, we focus on three interventions: antidepressants, pentosan polysulfate (PPS) and neuromuscular blockade. We selected these interventions on the basis that they are given 'strong recommendations' in the EAU Guidelines for management of BPS (EAU Guidelines 2019). We found very low-certainty evidence suggesting that antidepressants were associated with greater likelihood of cure or improvement compared with control (OR 5.91, 95% CrI 1.12 to 37.56), but it was uncertain whether they reduced pain (MD -1.27, 95% CrI -3.25 to 0.71; low-certainty evidence), daytime frequency (MD -2.41, 95% CrI -6.85 to 2.05; very low-certainty evidence) or nocturia (MD 0.01, 95% CrI -2.53 to 2.50; very low-certainty evidence). There was no evidence that PPS had improved cure/improvement rates (OR 0.14, 95% CrI 0.40 to 3.35; very low-certainty evidence) or reduced pain (MD 0.42, 95% CrI -1.04 to 1.91; low-certainty evidence), frequency (MD -0.37, 95% CrI -5.00 to 3.44; very low-certainty evidence) or nocturia (MD -1.20, 95% CrI -3.62 to 1.28; very low-certainty evidence). There was evidence that neuromuscular blockade resulted in greater cure or improvement (OR 5.80, 95% CrI 2.08 to 18.30) but no evidence that it improved pain (MD -0.33, 95% CrI -1.71 to 1.03), frequency (MD -0.91, 95% CrI -3.24, 1.29) or nocturia (MD -0.04, 95% CrI -1.35 to 1.27). The certainty of this evidence was always very low.

AUTHORS' CONCLUSIONS

We are uncertain whether some treatments may be effective in treating patients with BPS because the certainty of evidence was generally low or very low. Data were available for a relatively large number of trials, but most had small sample sizes and effects of treatments often could not be estimated with precision. An NMA was successfully conducted, but limited numbers of small trials for each treatment category hampered our ability to fully exploit the advantages of this analysis. Larger, more focused trials are needed to improve the current evidence base.

Role of neurogenic inflammation in local communication in the visceral mucosa

Intense research has focused on the involvement of the nervous system in regard to cellular mechanisms underlying neurogenic inflammation in the pelvic viscera. Evidence supports the neural release of inflammatory factors, trophic factors, and neuropeptides in the initiation of inflammation. However, more recently, non-neuronal cells including epithelia, endothelial, mast cells, and paraneurons are likely important participants in nervous system functions. For example, the urinary bladder urothelial cells are emerging as key elements in the detection and transmission of both physiological and nociceptive stimuli in the lower urinary tract. There is mounting evidence that these cells are involved in sensory mechanisms and can release mediators. Further, localization of afferent nerves next to the urothelium suggests these cells may be targets for transmitters released from bladder nerves and that chemicals released by urothelial cells may alter afferent excitability. Modifications of this type of communication in a number of pathological conditions can result in altered release of epithelial-derived mediators, which can activate local sensory nerves. Taken together, these and other findings highlighted in this review suggest that neurogenic inflammation involves complex anatomical and physiological interactions among a number of cell types in the bladder wall. The specific factors and pathways that mediate inflammatory responses in both acute and chronic conditions are not well understood and need to be further examined. Elucidation of mechanisms impacting on these pathways may provide insights into the pathology of various types of disorders involving the pelvic viscera.

Receptors, channels, and signalling in the urothelial sensory system in the bladder

The storage and periodic elimination of urine, termed micturition, requires a complex neural control system to coordinate the activities of the urinary bladder, urethra, and urethral sphincters. At the level of the lumbosacral spinal cord, lower urinary tract reflex mechanisms are modulated by supraspinal controls with mechanosensory input from the urothelium, resulting in regulation of bladder contractile activity. The specific identity of the mechanical sensor is not yet known, but considerable interest exists in the contribution of transient receptor potential (TRP) channels to the mechanosensory functions of the urothelium. The sensory, transduction, and signalling properties of the urothelium can influence adjacent urinary bladder tissues including the suburothelial nerve plexus, interstitial cells of Cajal, and detrusor smooth muscle cells. Diverse stimuli, including those that activate TRP channels expressed by the urothelium, can influence urothelial release of chemical mediators (such as ATP). Changes to the urothelium are associated with a number of bladder pathologies that underlie urinary bladder dysfunction. Urothelial receptor and/or ion channel expression and the release of signalling molecules (such as ATP and nitric oxide) can be altered with bladder disease, neural injury, target organ inflammation, or psychogenic stress. Urothelial receptors and channels represent novel targets for potential therapies that are intended to modulate micturition function or bladder sensation.

Bladder afferent hyperexcitability in bladder pain syndrome/interstitial cystitis

Bladder pain syndrome/interstitial cystitis is a disease with lower urinary tract symptoms, such as bladder pain and urinary frequency, which results in seriously impaired quality of life of patients. The extreme pain and urinary frequency are often difficult to treat. Although the etiology of bladder pain syndrome/interstitial cystitis is still not known, there is increasing evidence showing that afferent hyperexcitability as a result of neurogenic bladder inflammation and urothelial dysfunction is important to the pathophysiological basis of symptom development. Further investigation of the pathophysiology will lead to the effective treatment of patients with bladder pain syndrome/interstitial cystitis.

Neural control of the lower urinary tract

This article summarizes anatomical, neurophysiological, pharmacological, and brain imaging studies in humans and animals that have provided insights into the neural circuitry and neurotransmitter mechanisms controlling the lower urinary tract. The functions of the lower urinary tract to store and periodically eliminate urine are regulated by a complex neural control system in the brain, spinal cord, and peripheral autonomic ganglia that coordinates the activity of smooth and striated muscles of the bladder and urethral outlet. The neural control of micturition is organized as a hierarchical system in which spinal storage mechanisms are in turn regulated by circuitry in the rostral brain stem that initiates reflex voiding. Input from the forebrain triggers voluntary voiding by modulating the brain stem circuitry. Many neural circuits controlling the lower urinary tract exhibit switch-like patterns of activity that turn on and off in an all-or-none manner. The major component of the micturition switching circuit is a spinobulbospinal parasympathetic reflex pathway that has essential connections in the periaqueductal gray and pontine micturition center. A computer model of this circuit that mimics the switching functions of the bladder and urethra at the onset of micturition is described. Micturition occurs involuntarily in infants and young children until the age of 3 to 5 years, after which it is regulated voluntarily. Diseases or injuries of the nervous system in adults can cause the re-emergence of involuntary micturition, leading to urinary incontinence. Neuroplasticity underlying these developmental and pathological changes in voiding function is discussed.

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.

Neural mechanisms underlying lower urinary tract dysfunction

This article summarizes anatomical, neurophysiological, and pharmacological studies in humans and animals to provide insights into the neural circuitry and neurotransmitter mechanisms controlling the lower urinary tract and alterations in these mechanisms in lower urinary tract dysfunction. The functions of the lower urinary tract, to store and periodically release urine, are dependent on the activity of smooth and striated muscles in the bladder, urethra, and external urethral sphincter. During urine storage, the outlet is closed and the bladder smooth muscle is quiescent. When bladder volume reaches the micturition threshold, activation of a micturition center in the dorsolateral pons (the pontine micturition center) induces a bladder contraction and a reciprocal relaxation of the urethra, leading to bladder emptying. During voiding, sacral parasympathetic (pelvic) nerves provide an excitatory input (cholinergic and purinergic) to the bladder and inhibitory input (nitrergic) to the urethra. These peripheral systems are integrated by excitatory and inhibitory regulation at the levels of the spinal cord and the brain. Therefore, injury or diseases of the nervous system, as well as disorders of the peripheral organs, can produce lower urinary tract dysfunction, leading to lower urinary tract symptoms, including both storage and voiding symptoms, and pelvic pain. Neuroplasticity underlying pathological changes in lower urinary tract function is discussed.

Effects of combination treatment of intravesical resiniferatoxin instillation and hydrodistention in patients with refractory painful bladder syndrome/interstitial cystitis: a pilot study

PURPOSE

Painful bladder syndrome/interstitial cystitis (PBS/IC) is a disabling disease of the urinary bladder, and its etiology and treatment are not yet established. Current medications used in the treatment of PBS/IC have shown limited efficacy. This prospective study investigated the efficacy of intravesical resiniferatoxin (RTX) in PBS/IC refractory to medical treatment.

METHODS

Patients with proven PBS/IC refractory to traditional medical treatment were enrolled. By randomized trial, a total of 18 consecutive patients were divided into two groups: treatment with hydrodistention and intravesical RTX (group 1) or treatment with hydrodistension only (group 2). We assessed bladder pain by use of a visual analogue pain scale, the maximal urine flow rate, post-void residual urine volume, and a voiding diary before and 3 months after treatment.

RESULTS

The median age of the 18 patients was 55.8±6.9 years, and the median duration of symptoms before diagnosis was 3.6±1.6 years. Frequency, functional bladder capacity, and score on a 5-point pain scale were significantly improved at 3-month after treatment in both groups. Intravesical RTX instillation plus hydrodistention, compared with hydrodistention only, did not have a significant effect on the voiding symptoms or uroflowmetry of the patients but significantly improved scores on the pain scale.

CONCLUSIONS

Intravesical RTX instillation plus hydrodistention was effective in relieving pain but was not effective in improving lower urinary tract symptoms. Further larger studies are needed to clarify the efficacy of combination treatment of intravesical RTX instillation and hydrodistention.

An investigation of the safety and pharmacokinetics of the novel TRPV1 antagonist XEN-D0501 in healthy subjects

AIMS

XEN-D0501, a novel TRPV1 antagonist, is being developed to treat overactive bladder. This study investigated the safety and pharmacokinetics of repeat-dose XEN-D0501 in healthy subjects.

METHODS

The study was conducted in two parts. Part 1 was a double-blind, randomized, placebo-controlled, two-way crossover study in three cohorts of 12 young male subjects. Each subject received XEN-D0501 and placebo (in random order) twice daily for 13 days, with a final single dose on day 14. Doses of 1, 2.5 and 5 mg XEN-D0501 were investigated. Part 2 was an open-label, randomized, two-way crossover study in male and female subjects (45 to 65 years). Subjects received single doses of 5 mg XEN-D0501 under fasted and fed conditions in random order. Blood sampling and safety assessments were conducted throughout the study.

RESULTS

XEN-D0501 was rapidly absorbed (t_max generally 0.5–4 h post dose). XEN-D0501 exposure increased less than proportionally to dose over the range studied and exhibited minimal accumulation with twice daily dosing. Food had no clinically relevant effects on the pharmacokinetics of XEN-D0501. There were no severe or serious adverse events and all doses were well tolerated. A dose-related increase in body temperature was seen with XEN-D0501 which attenuated over time. Differences from placebo in mean maximum core body temperatures were 0.22°C, 0.5°C and 0.74°C following 1 mg, 2.5 mg and 5 mg twice daily XEN-D0501. The observed increase in body temperature was not considered to be of clinical concern.

CONCLUSIONS

XEN-D0501 appeared safe and well tolerated at doses up to 5 mg twice daily for 14 days in healthy subjects.

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.

Afferent mechanism in the urinary tract

Much of the current research on lower urinary tract dysfunction is focused on afferent mechanisms. The main goals are to define and modulate the signaling pathways by which afferent information is generated and conveyed to the central nervous system. Alterations in bladder afferent mechanisms are a potential source of voiding dysfunction and an emerging source of drug targets. Even some established drug therapies such as muscarinic receptor antagonists, as well as emerging therapies such as botulinum toxin type-A, may act partly through afferent mechanisms. This review presents up-to-date findings on the localization of afferent fiber types within the bladder wall, afferent receptors and transmitters, and how these may communicate with the urothelium, interstitial cells, and detrusor smooth muscle to regulate micturition in normal and pathological bladders. Peripheral and central mechanisms of afferent sensitization and myogenic mechanisms that lead to detrusor overactivity, overactive bladder symptoms, and urgency sensations are also covered as well as new therapeutic approaches and new and established methods of measuring afferent activity.

Intravesical drug delivery: Challenges, current status, opportunities and novel strategies

The urinary bladder has certain unique anatomical features which enable it to form an effective barrier to toxic substances diffusing from the urine into the blood. The barrier function is due to the epithelial surface of the urinary bladder, the urothelium, which has characteristic umbrella cells, joined by tight junctions and covered by impenetrable plaques, as well as an anti-adherent mucin layer. Diseases of the urinary bladder, such as bladder carcinomas and interstitial cystitis, cause acute damage to the bladder wall and cannot be effectively treated by systemic administration of drugs. Such conditions may benefit from intravesical drug delivery (IDD), which involves direct instillation of drug into the bladder via a catheter, to attain high local concentrations of the drug with minimal systemic effects. IDD however has its limitations, since the permeability of the urothelial layer is very low and instilled drug solutions become diluted with urine and get washed out of the bladder during voiding, necessitating repeated infusions of the drug. Permeation enhancers serve to overcome these problems to some extent by using electromotive force to enhance diffusion of the drug into the bladder wall or chemical molecules, such as chitosan, dimethylsulphoxide, to temporarily disrupt the tight packing of the urothelium. Nanotechnology can be integrated with IDD to devise drug-encapsulated nanoparticles that can greatly improve chemical interactions with the urothelium and enhance penetration of drugs into the bladder wall. Nanocarriers such as liposomes, gelatin nanoparticles, polymeric nanoparticles and magnetic particles, have been found to enhance local drug concentrations in the bladder as well as target diseased cells. Intravesical drug carriers can be further improved by using mucoadhesive biomaterials which are strongly adhered to the urothelial cell lining, thus preventing the carrier from being washed away during urine voiding. This increases the residence time of the drug at the target site and enables sustained delivery of the drug over a prolonged time span. Polymeric hydrogels, such as the temperature sensitive PEG-PLGA-PEG polymer, have been used to develop in situ gelling systems to deliver drugs into the bladder cavity. Recent advances and future prospects of biodegradable nanocarriers and in situ gels as drug delivery agents for intravesical drug delivery are reviewed in this paper.

Afferent nerve regulation of bladder function in health and disease

The afferent innervation of the urinary bladder consists primarily of small myelinated (Adelta) and unmyelinated (C-fiber) axons that respond to chemical and mechanical stimuli. Immunochemical studies indicate that bladder afferent neurons synthesize several putative neurotransmitters, including neuropeptides, glutamic acid, aspartic acid, and nitric oxide. The afferent neurons also express various types of receptors and ion channels, including transient receptor potential channels, purinergic, muscarinic, endothelin, neurotrophic factor, and estrogen receptors. Patch-clamp recordings in dissociated bladder afferent neurons and recordings of bladder afferent nerve activity have revealed that activation of many of these receptors enhances neuronal excitability. Afferent nerves can respond to chemicals present in urine as well as chemicals released in the bladder wall from nerves, smooth muscle, inflammatory cells, and epithelial cells lining the bladder lumen. Pathological conditions alter the chemical and electrical properties of bladder afferent pathways, leading to urinary urgency, increased voiding frequency, nocturia, urinary incontinence, and pain. Neurotrophic factors have been implicated in the pathophysiological mechanisms underlying the sensitization of bladder afferent nerves. Neurotoxins such as capsaicin, resiniferatoxin, and botulinum neurotoxin that target sensory nerves are useful in treating disorders of the lower urinary tract.

Excitatory and inhibitory urinary bladder reflexes induced by stimulation of cervicovaginal capsaicin-sensitive sensory fibers in rats

We have investigated the effect of intravaginal application of capsaicin on micturition reflex in female rats. Urinary bladder contractility was measured by transurethral pressure recording at isovolumetric and subthreshold conditions in anaesthetized rats. The intravaginal application of capsaicin (15 microg/50 microl rat) induced reproducible bladder phasic contractions, without desensitization upon repeated applications, that were blocked by intravenous atropine (1 mg/kg) or hexamethonium (5 mg/kg) and prevented by removal of paracervical ganglia or systemic capsaicin pretreatment (125 mg/kg, s.c.). The inhibition of sympathetic transmission by guanethidine (30 mg/kg, s.c.) produced significant increase of the bladder reflex contractions activated by intravaginal capsaicin. Intravenous administration of the TRPV1 antagonist, capsazepine (3 mg/kg), significantly reduced the excitatory reflex response to capsaicin. Intravaginal administration of capsaicin (15 microg/50 microl), during distension-induced reflex bladder contractions, produced a transient block of reflexes, unaffected by guanethidine pretreatment. In conclusion, the stimulation of capsaicin-sensitive sensory nerve endings in the rat cervix-vagina induced a dual excitatory or inhibitory bladder response in anaesthetized female rats depending on the degree of bladder distension.

Intravesical treatments for painful bladder syndrome/ interstitial cystitis

BACKGROUND

Painful Bladder Syndrome/Interstitial Cystitis (PBS/IC) occurs predominantly in women. It is a poorly-understood condition with symptoms of bladder pain, urinary frequency, urgency and nocturia. Treatments for PBS/IC include dietary/lifestyle interventions, oral medication, intravesical instillations and, in some cases, surgery. Success rates are generally modest and there is little consensus as to the best form of treatment for this condition.

OBJECTIVES

To assess the effectiveness of intravesical treatment for PBS/IC.

SEARCH STRATEGY

We searched the Cochrane Incontinence Group specialised trials register (30 May 2006) as well as reference lists of all selected trials. Recognised researchers in the field were contacted for any additional relevant material.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials were included in the review if they had recruited participants with a clinical diagnosis of PBS/IC and if at least one arm of the trial was treatment with an intravesical preparation. Outcome measures were pre-determined, the primary ones being the effect on pain and bladder capacity. Others included symptomatic response to treatment, quality-of-life assessment, economic factors and adverse events.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial eligibility and quality, then extracted relevant data from the studies.

MAIN RESULTS

Nine eligible trials were identified - six parallel group, one incomplete cross-over and two cross-over trials - with a total of 616 participants. Six trials compared an 'active' instillation with placebo instillation, two compared different types of instillation, and one was a comparison of an instillation plus bladder training versus bladder training alone. Altogether, the review included trials of six different types of intravesical instillation: Resiniferatoxin, Dimethyl sulfoxide, BCG, pentosanpolysulphate, oxybutin, and alkalinisation of urine pH. Confidence intervals were generally wide. Resiniferatoxin was not associated with sustained differences in the review outcomes reported but pain during instillation and withdrawal from treatment was significantly more common. The data available about Dimethyl sulfoxide (DMSO) were very limited but with no apparent differences from placebo. Groups treated with BCG tended to report less pain and fewer general symptoms. Although adverse events were commonly reported, these were no more common after BCG than after placebo instillation. The few data about Pentosanpolysulphate tended to favour the actively treated, but with wide confidence intervals; there was little information about adverse events. Oxybutinin instillation was associated with increased bladder capacity, reduced frequency, improved quality of life scores and fewer drop-outs. Alkalinisation of urine pH did not make any clear difference, but with potentially wide confidence intervals.

AUTHORS' CONCLUSIONS

Overall, the evidence base for treating PBS/IC using intravesical preparations is limited and the potential for meta-analysis reduced by variation in the outcome measures used. The quality of trial reports was mixed and in some cases this precluded any meaningful data extraction. BCG and oxybutin are reasonably well-tolerated and evidence is most promising for these. Resiniferatoxin showed no evidence of effect for most outcomes and caused pain, which reduced treatment compliance. There is little evidence for the other treatments included in this review. Randomised controlled trials are still needed and study design should incorporate outcomes that are most relevant to these with PBS/IC and should be standardised.

On the origin of bladder sensing: Tr(i)ps in urology

The mammalian TRP family consists of 28 channels that can be subdivided into 6 different classes: TRPV (vanilloid), TRPC (canonical), TRPM (Melastatin), TRPP (Polycystin), TRPML (Mucolipin), and TRPA (Ankyrin). TRP channels are activated by a diversity of physical (voltage, heat, cold, mechanical stress) or chemical (pH, osmolality) stimuli and by binding of specific ligands, enabling them to act as multifunctional sensors at the cellular level. Currently, a lot of scientific research is devoted to these channels and their role in sensing mechanisms throughout the body. In urology, there's a growing conviction that disturbances in afferent (sensory) mechanisms are highly important in the pathogenesis of functional problems. Therefore, the TRP family forms an interesting new target to focus on. In this review we attempt to summarize the existing knowledge about TRP channels in the urogenital tract. So far, TRPV1, TRPV2, TRPV4, TRPM8, and TRPA1 have been described in different parts of the urogenital tract. Although only TRPV1 (the vanilloid receptor) has been extensively studied so far, more evidence is slowly accumulating about the role of other TRP channels in the (patho)physiology of the urogenital tract.

Multiple Intravesical Instillations of Low-Dose Resiniferatoxin in the Treatment of Refractory Interstitial Cystitis

BACKGROUND

Current medications used in the treatment of interstitial cystitis (IC) have limited efficacy. This prospective study investigated the efficacy of multiple intravesical instillations of resiniferatoxin (RTX) at the concentration of 10 nM.

METHODS

Patients with proven IC previously treated with traditional medications for more than 6 months without clinical benefit were enrolled. They were excluded if bladder outlet obstruction or urinary tract infection was present. Intravesical instillation of low-dose RTX (10 nM) once weekly for 4 weeks was performed at the outpatient department. International Prostate Symptom Score (IPSS), 5-Point Pain Scale, and Quality of Life Index (QOL Index) were recorded. A videourodynamic study was done at baseline and 3 months after treatment.

RESULTS

The therapeutic results and urodynamic parameters were compared between baseline and 3 months. Thirteen patients, including 10 women and 3 men, were enrolled in this study. The mean duration of IC symptoms was 4.4 +/- 2.5 years. The mean duration of active treatment was 15.3 +/- 8.6 months. One female patient dropped out due to severe bladder pain after RTX instillation. Among the 12 patients who completed the study treatment, subjective assessment revealed that 2 had an excellent therapeutic result, 5 had an improved result and 5 remained unchanged from baseline. The overall satisfactory rate was 58.3%. IPSS, 5-Point Pain Scale, and QOL Index were significantly decreased after RTX treatment. There was no significant increase in mean functional bladder capacity or change in urodynamic parameters. No serious adverse event occurred after RTX treatment.

CONCLUSIONS

This study suggests that multiple intravesical instillations of RTX at the concentration of 10 nM are effective in relieving lower urinary tract symptoms in patients with refractory IC. The treatment is tolerable and suitable for use on an outpatient clinic basis.

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.

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.

Heat/burning sensation induced by topical application of capsaicin on perineal cutaneous area: New approach in diagnosis and treatment of chronic prostatitis/chronic pelvic pain syndrome?

OBJECTIVES

To investigate the feasibility, safety, and efficacy of perineal cutaneous application of capsaicin as a test for the diagnosis, as well as a potential therapeutic tool, in patients with chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS).

METHODS

We recruited 22 patients (mean age 34.5 years, range 19 to 56), who had been diagnosed with CP/CPPS according to the National Institutes of Health criteria, and 6 healthy control subjects. Both groups received a topical application of 5 mL capsaicin at a concentration of 10(-5) M to the perineal body skin. The patients were asked to mark on a visual analogue scale the intensity of any heat or burning sensation. All the patients had completed a National Institutes of Health Chronic Prostatitis Symptom Index before and 1 week after the test. The scores of the two groups were compared using the Mann-Whitney U test.

RESULTS

The patients with CP/CPPS reported a heat/burning sensation intensity that was statistically greater than that of the healthy controls (7.5 versus 4.3, P <0.001) and a shorter time to heat sensation onset and maximal intensity (1.5 versus 3.4 minutes, P <0.001, and 2.5 versus 7 minutes, P <0.001, respectively). Of the 22 patients, 16 reported an improvement of symptoms after 7 days and the mean National Institutes of Health Chronic Prostatitis Symptom Index score decreased from 27 to 16 (P <0.01).

CONCLUSIONS

We found a statistically significant difference in the pain visual analogue scale and interval between topical application and the onset of the heat/burning sensation between patients with CP/CPPS and healthy controls. The small sample size strongly suggests the need for additional larger and more controlled studies.

Intravesical Therapy for Overactive Bladder

Overactive bladder and urgency incontinence are common conditions generally treated with oral anticholinergic therapy. Despite the development of new antimuscarinic agents, many patients do not tolerate or fail to respond to oral therapy. Intravesical instillation therapy can provide an alternative method of managing bladder overactivity. Intravesical instillation of anticholinergics such as oxybutynin and atropine can achieve cholinergic blockade without producing systemic side effects. Botulinum A toxin injected directly into the detrusor has been shown in preliminary studies to increase bladder capacity and decrease uncontrolled bladder contractility for up to 6 months. Intravesical local anesthetics such as lidocaine and bupivacaine block the conduction of unmyelinated C fibers and when administered into the bladder, lead to an increase in functional bladder capacity. Intravesical capsaicin and resiniferatoxin also affect afferent innervation by blocking C-fiber afferents, leading to decreased bladder contractility and increased bladder capacity. Intravesical instillation therapy can provide an alternative treatment for the management of overactive bladder.

Intravesical resiniferatoxin for the treatment of interstitial cystitis: a randomized, double-blind, placebo controlled trial

PURPOSE

Interstitial cystitis is a painful bladder condition of unknown etiology and poorly understood pathophysiology. Current therapies have met with limited success. Vanilloid receptor agonists such as resiniferatoxin (RTX) desensitize C-fibers that transmit pain; it is hypothesized that such drugs will be effective in the treatment of interstitial cystitis and painful bladder syndrome by decreasing the pain that leads to urinary frequency and urgency.

MATERIALS AND METHODS

A randomized, double-blind, placebo controlled study was conducted in 163 patients with interstitial cystitis. Participants were randomly assigned to receive a single intravesical dose of 50 ml of either RTX 0.01 microM, 0.05 microM, 0.10 microM, or placebo. Safety and efficacy was evaluated over 12 weeks. The primary efficacy endpoint was the Global Response Assessment, a 7-point scale rating overall change in symptoms of interstitial cystitis after 4 weeks. Secondary efficacy endpoints included reduction in pain, urgency, frequency, nocturia, average void volume, and the O'Leary-Sant Symptom and Problem Indexes.

RESULTS

RTX did not improve overall symptoms, pain, urgency, frequency, nocturia, or average void volume during 12 weeks followup. RTX resulted in a dose-dependent increase in the incidence of instillation pain, but was otherwise generally well tolerated.

CONCLUSIONS

In the largest prospective, randomized clinical trial reported to date with intravesical vanilloid therapy, single administration of RTX at doses of 0.01 microM to 0.10 microM was not effective in patients with interstitial cystitis.

Treatment of interstitial cystitis

Although the symptoms of interstitial cystitis (IC)--a debilitating, chronic disease characterized by urinary urgency and frequency, and bladder and pelvic pain on bladder filling--are easily confused with those of urinary tract infections, there is an absence of an underlying infection, and antibiotic therapy is of no therapeutic benefit. Severe cases of this disorder, which affects mainly women, can have a great negative impact on the quality of life of patients because of extreme urinary frequency. The diagnosis of IC is difficult and should be based on patient history, physical examination, and cystoscopy. A large number of pharmacologic treatments have been used to treat this condition with limited success, including pentosan polysulfate, heparin, antihistamines, tricyclic antidepressants, intravesical dimethyl sulfoxide, and bacille Calmette-Guérin. Among the potentially effective new treatment modalities currently under investigation are suplatast tosilate, resiniferatoxin, botulinum toxin, and gene therapy to modulate the pain response. As knowledge of the pathogenesis of IC increases through intensified research, the ability to provide effective treatment to patients with this disease will improve.

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.

Spinal neurophysiologic correlates of the analgesic actions of intravesical dimethyl sulfoxide and capsaicin in the rat

Peripheral analgesia produced by the intravesical instillation of dimethyl sulphoxide (DMSO) and capsaicin has been used to treat visceral pain originating in the urinary bladder. The present study sought to determine the neurophysiologic consequences of the intravesical instillation of these compounds by measuring spinal neuronal responses evoked by urinary bladder distension (UBD) in the rat. Subjects were spinally transected, decerebrate female Sprague-Dawley rats. The effect of 0.5 mL of solution of 10% or 50% DMSO, 100 micromol/L capsaicin, or the same volume of saline instilled into the bladder on excitatory neuronal responses to UBD was studied by using single-unit extracellular recordings of L6-S2 dorsal horn spinal cord neurons. Fifty-six dorsal horn neurons that were excited by UBD in a graded fashion were identified. All neurons were also excited by noxious or non-noxious cutaneous stimuli. Two hours after intravesical instillation, solutions of 50% DMSO or 100 micromol/L of capsaicin produced a reduction of the slope of stimulus-response functions for neuronal activity evoked by graded UBD. These data support a local effect of intravesical 50% DMSO or capsaicin and suggest the use of this model to study novel peripheral treatment strategies for bladder pain.

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.

Metabolism of capsaicin by cytochrome P450 produces novel dehydrogenated metabolites and decreases cytotoxicity to lung and liver cells

Capsaicin is a common dietary constituent and a popular homeopathic treatment for chronic pain. Exposure to capsaicin has been shown to cause various dose-dependent acute physiological responses including the sensation of burning and pain, respiratory depression, and death. In this study, the P450-dependent metabolism of capsaicin by recombinant P450 enzymes and hepatic and lung microsomes from various species, including humans, was determined. A combination of LC/MS, LC/MS/MS, and LC/NMR was used to identify several metabolites of capsaicin that were generated by aromatic (M5 and M7) and alkyl hydroxylation (M2 and M3), O-demethylation (M6), N- (M9) and alkyl dehydrogenation (M1 and M4), and an additional ring oxygenation of M9 (M8). Dehydrogenation of capsaicin was a novel metabolic pathway and produced unique macrocyclic, diene, and imide metabolites. Metabolism of capsaicin by microsomes was inhibited by the nonselective P450 inhibitor 1-aminobenzotriazole (1-ABT). Metabolism was catalyzed by CYP1A1, 1A2, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4. Addition of GSH (2 mM) to microsomal incubations stimulated the metabolism of capsaicin and trapped several reactive electrophilic intermediates as their GSH adducts. These results suggested that reactive intermediates, which inactivated certain P450 enzymes, were produced during catalytic turnover. Comparison of the rate and types of metabolites produced from capsaicin and its analogue, nonivamide, demonstrated similar pathways in the P450-dependent metabolism of these two capsaicinoids. However, production of the dehydrogenated (M4), macrocyclic (M1), and omega-1-hydroxylated (M3) metabolites was not observed for nonivamide. These differences may be reflective of the mechanism of formation of these metabolites of capsaicin. The role of metabolism in the cytotoxicity of capsaicin and nonivamide was also assessed in cultured lung and liver cells. Lung cells were markedly more sensitive to cytotoxicity by capsaicin and nonivamide. Cytotoxicity was enhanced 5 and 40% for both compounds by 1-ABT in BEAS-2B and HepG2, respectively. These data suggested that metabolism of capsaicinoids by P450 in cells represented a detoxification mechanism (in contrast to bioactivation).

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.

Altered urinary bladder function in mice lacking the vanilloid receptor TRPV1

In the urinary bladder, the capsaicin-gated ion channel TRPV1 is expressed both within afferent nerve terminals and within the epithelial cells that line the bladder lumen. To determine the significance of this expression pattern, we analyzed bladder function in mice lacking TRPV1. Compared with wild-type littermates, trpv1(-/-) mice had a higher frequency of low-amplitude, non-voiding bladder contractions. This alteration was accompanied by reductions in both spinal cord signaling and reflex voiding during bladder filling (under anesthesia). In vitro, stretch-evoked ATP release and membrane capacitance changes were diminished in bladders excised from trpv1(-/-) mice, as was hypoosmolality-evoked ATP release from cultured trpv1(-/-) urothelial cells. These findings indicate that TRPV1 participates in normal bladder function and is essential for normal mechanically evoked purinergic signaling by the urothelium.

Quantitative analysis of the dendrites of sacral preganglionic neurons in the cat

Quantitative analyses were performed on the dendrites and somata of 25 electrophysiologically identified preganglionic neurons (PGN) obtained from the sacral spinal cord of the cat by intracellular injection of Neurobiotin or horseradish peroxidase. Total dendritic length and surface area were measured for each dendrite. The sizes of the stem dendrites measured at their base were positively correlated with the sizes of the entire tree and numbers of end branches. Total surface area of somata and dendrites averaged 39,138 microm(2); 90.7% of that was from the dendrites. To obtain measurements of the relative contributions of PGN dendrites to specific regions of the spinal cord, the percentage of each dendrite occupying eight spinal cord regions was recorded. Sixty-three percent of the dendrites projected dorsal to their somata, whereas an average of 33.3% of dendrites were located in the white matter, most of them in the lateral and dorsolateral funiculi. The neurons within this sample formed a continuum with some neurons having a large percentage of dendrites in lamina I but little in the white matter, whereas at the other end of the continuum were cells with the reverse configuration. The intermediate neurons had dendrites in both locations. Taken together, these data indicate a heterogeneous population of PGN in the lateral band of the sacral parasympathetic nucleus.

The capsaicin analogue SDZ249-665 attenuates the hyper-reflexia and referred hyperalgesia associated with inflammation of the rat urinary bladder

This study assessed the effects of the systemically administered capsaicin analogue SDZ249-665 in an animal model of visceral pain and hyper-reflexia. The effects of prophylactic administration of SDZ249-665 (in the dose range 0.05-1 mg/kg) on the viscero-visceral hyper-reflexia (VVH) and the referred viscero-somatic hyperalgesia to mechanical stimuli (VSH) associated with turpentine inflammation of the rat urinary bladder were evaluated. SDZ249-665 attenuated both the VVH and the VSH in a dose related fashion. In the VVH model, following solvent control administration, intra-vesical turpentine administration was associated with a significant reduction in micturition threshold to 43.7% (SEM 6.3) of baseline, indicating the presence of a VVH. This effect was not observed when animals were prophylactically treated with SDZ249-665 alone. At a dose of 0.1 mg/kg the micturition threshold was 90.7% (SEM 10.2) of baseline at 1 h after intra-vesical instillation of turpentine. In the VSH model, curves were plotted of the difference in fore and hind limb withdrawal latencies from a mechanical stimulus and the area under these curves (AUCs) were compared between different treatment protocols. Intra-vesical turpentine was associated with a negative deflection of the curve (AUC -5.2x10(3) SEM 1.7) in comparison with naïve animals (AUC -0.02x10(3) SEM 0.6), indicative of a referred hyperalgesia. This was prevented, in a dose-related manner, by prophylactic administration of SDZ249-665. For example, at a dose of 0.5 mg/kg the AUC was +0.4x10(3) (SEM 0.8). These findings support previous work indicating that capsaicin sensitive neurones participate in patho-physiological events occurring following inflammation of the bladder, and provides evidence that systemically active capsaicin based compounds may be developed for use in the clinical setting.

Advancements in pharmacologic management of the overactive bladder

Continued developments in the understanding of lower urinary tract function have led to improvements in the pharmacologic manipulation of bladder dysfunction. Drug delivery changes have produced drugs that provide better efficacy and tolerability, thus improving patient compliance. Improvements in drug delivery systems have altered drug bioavailability and pharmacokinetics. Active current investigation in new agents and delivery systems for intravesical delivery has yielded intriguing early results that may substantially add to the armamentarium for the management of the overactive bladder (urgency, frequency, urge incontinence). New developments in the understanding of the neuropharmacology of the bladder, peripheral pelvic nerves, and sacral cord may provide agents with entirely new drug effects, either as primary agents or agents to be used in combination with currently available drugs. We herein review newer agents and drug delivery systems.