Intravesical Vanilloids and Neurogenic Incontinence: Ten Years Experience

Euphorbia bicolor (Euphorbiaceae) Latex Phytochemicals Induce Long-Lasting Non-Opioid Peripheral Analgesia in a Rat Model of Inflammatory Pain

The negative side effects of opioid-based narcotics underscore the search for alternative non-opioid bioactive compounds that act on the peripheral nervous system to avoid central nervous system-mediated side effects. The transient receptor potential V1 ion channel (TRPV1) is a peripheral pain generator activated and sensitized by heat, capsaicin, and a variety of endogenous ligands. TRPV1 contributes to peripheral sensitization and hyperalgesia, in part, via triggering the release of proinflammatory peptides, such as calcitonin gene-related peptide (CGRP), both locally and at the dorsal horn of the spinal cord. Ultrapotent exogenous TRPV1 agonists, such as resiniferatoxin identified in the latex of the exotic Euphorbia resinifera, trigger hyperalgesia followed by long lasting, peripheral analgesia. The present study reports on the analgesic properties of Euphorbia bicolor, a relative of E. resinifera, native to the Southern United States. The study hypothesized that E. bicolor latex extract induces long-lasting, non-opioid peripheral analgesia in a rat model of inflammatory pain. Both inflamed and non-inflamed adult male and female rats were injected with the methanolic extract of E. bicolor latex into the hindpaw and changes in pain behaviors were reassessed at various time points up to 4 weeks. Primary sensory neuron cultures also were treated with the latex extract or vehicle for 15 min followed by stimulation with the TRPV1 agonist capsaicin. Results showed that E. bicolor latex extract evoked significant pain behaviors in both male and female rats at 20 min post-injection and lasting around 1–2 h. At 6 h post-injection, analgesia was observed in male rats that lasted up to 4 weeks, whereas in females the onset of analgesia was delayed to 72 h post-injection. In sensory neurons, latex extract significantly reduced capsaicin-evoked CGRP release. Blocking TRPV1, but not opioid receptors, attenuated the onset of analgesia and capsaicin-induced CGRP release. Latex was analyzed by mass spectrometry and eleven candidate compounds were identified and reported here. These findings indicate that phytochemicals in the E. bicolor latex induce hyperalgesia followed by peripheral, non-opioid analgesia in both male and female rats, which occurs in part via TRPV1 and may provide novel, non-opioid peripheral analgesics that warrant further examination.

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

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

Pathophysiology, Clinical Importance, and Management of Neurogenic Lower Urinary Tract Dysfunction Caused by Suprasacral Spinal Cord Injury

Management of persistent lower urinary tract dysfunction resulting from severe thoracolumbar spinal cord injury can be challenging. Severe suprasacral spinal cord injury releases the spinal cord segmental micturition reflex from supraspinal modulation and increases nerve growth factor concentration in the bladder wall, lumbosacral spinal cord, and dorsal root ganglion, which subsequently activates hypermechanosensitive C-fiber bladder wall afferents. Hyperexcitability of bladder afferents and detrusor overactivity can cause urine leaking during the storage phase. During urine voiding, the loss of supraspinal control that normally coordinates detrusor contraction with sphincter relaxation can lead to spinal cord segmental reflex-mediated simultaneous detrusor and sphincter contractions or detrusor-sphincter dyssynergia, resulting in inefficient urine voiding and high residual volume. These disease-associated changes can impact on the quality of life and life expectancy of spinal-injured animals. Here, we discuss the pathophysiology and management considerations of lower urinary tract dysfunction as the result of severe, acute, suprasacral spinal cord injury. In addition, drawing from experimental, preclinical, and clinical medicine, we introduce some treatment options for neurogenic lower urinary tract dysfunction that are designed to: (1) prevent urine leakage arising because of detrusor overactivity during bladder filling, (2) preserve upper urinary tract integrity and function by reducing intravesical pressure and subsequent vesicoureteral reflux, and (3) prevent urinary tract and systemic complications by treating and preventing urinary tract infections.

Innovative pharmacotherapies for women with overactive bladder: where are we now and what is in the pipeline?

INTRODUCTION AND HYPOTHESIS

The impressive prevalence of overactive bladder (OAB) and the relevant limitations of current treatments urge the need for novel therapeutic approaches.

METHODS

A systematic literature and web search was performed to identify investigational drugs that entered the early and late phases of clinical development for women with OAB symptoms.

RESULTS

Approved pharmacological therapies for OAB (antimuscarinics, beta-3 agonists, and botulinum toxin) are evolving with the development of alternative administration methods, combination strategies, and novel compounds, expected to improve effectiveness, bladder selectivity, and dose flexibility. A wealth of investigational compounds, developed with both public and companies' indoor nonclinical disease-oriented studies, entered the early and late stages of clinical development in the last decade. Most non-anticholinergic compounds in ongoing clinical trials target central and peripheral neurotransmitter receptors involved in neurological modulation of micturition, nonadrenergic-noncholinergic mechanisms, cyclic nucleotide metabolism, different subtypes of ion channels or peripheral receptors of prostaglandins, vanilloids, vitamin D3, and opioids. Fascinating advances are ongoing also in the field of genetic therapy.

CONCLUSIONS

New pharmaceutical formulations and drug combinations are expected to be available in the next decade in order to overcome the limitations of current drugs for OAB. Although proof-of-concept, patient-oriented studies yielded disappointing results for several tentative drugs, a lot of clinical research is ongoing that is expected to provide clinicians with novel therapeutic agents in the near future.

Use of vanilloids in urologic disorders

The bladder is an organ rich in vanilloid targets: dense unmyelinated c-fibers partially responsible for bladder sensation and response to noxious stimuli. Drugs such as capsaicin and resiniferatoxin (RTX) interact with the VR1 vanilloid receptor subtype to initially excite then subsequently desensitize the c-fibers. This chapter examines the literature describing the use of vanilloid receptor agonists in the treatment of the following urological disorders: neurogenic bladder (NGB), overactive bladder (OAB), and interstitial cystitis/painful bladder syndrome (IC/PBS). Review of the literature was performed using Pubmed and the following key words "capsaicin," "resiniferatoxin (RTX)," and "neurogenic bladder," "overactive bladder (OAB)," and "interstitial cystitis," "painful bladder syndrome." Articles focusing on randomized trials comparing intravesical administration of a vanilloid receptor agonist to placebo and those in English were reviewed. We conclude that capsaicin and RTX do appear to provide some acceptable treatment results in patients with neurogenic bladder, though larger studies are needed to confirm this. Although efficacy has been shown in some studies, currently the use of vanilloids cannot be recommended for routine use in patients with OAB as the need for catheterization may cause the risk to outweigh the benefit of treatment. Similarly, for the treatment of BPS, vanilloid receptor agonists lack strong evidence for efficacy or tolerability; larger studies are needed to define their role. Understanding how vanilloids are able to impact these disorders, however, may help further elucidate their underlying pathophysiological processes.

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.

Resiniferatoxin and tetrodotoxin induced NPY and TH immunoreactivity changes within the paracervical ganglion neurons supplying the urinary bladder

Both resiniferatoxin (RTX) and tetrodotoxin (TTX) have been reported to be effective in several urinary bladder dysfunction clinical trials. The aim of this study was to establish the effect of intravesical administration of RTX and TTX on neuropeptides Y (NPY) and tyrosine hydroxylase (TH) relationship in the paracervical ganglion (PCG) neurons supplying the urinary bladder in the pig. TH is an enzyme responsible for catalyzing the conversion of the amino acid L-tyrosine to dihydroxyphenylalanine (DOPA) and is used as a marker of catecholaminergic neurons. NPY augments the vasoconstrictor effects of noradrenergic neurons, and is involved in pathophysiological processes as a neuromodulator. To identify the PCG neurons supplying urinary bladder Fast Blue (FB) was injected into the bladder wall prior to intravesical RTX or TTX administration. Consequent application of immunocytochemical methods revealed that in control group 64.08 % of FB-positive PCG neurons contain NPY and 4.25 % TH. Intravesical infusion of RTX resulted upregulation of the NPY-IR neurons to 82.97 % and TH-IR to 43.78 %. Also administration of TTX induced further increase number of TH-IR neurons to 77.49 % but induced decrease number of NPY-IR neurons to 57.45 %. Both neurotoxins affect chemical coding of the PCG neural somata supplying urinary bladder, but the effects of their action are different. This results shed light on possible involvement of RTX and TTX on curing tissue, and potentially could help us to broaden our neurourological armamentarium.

TRP channels and analgesia

Since cloning and characterizing the first nociceptive ion channel Transient Receptor Potential (TRP) Vanilloid 1 (TRPV1), other TRP channels involved in nociception have been cloned and characterized, which include TRP Vanilloid 2 (TRPV2), TRP Vanilloid 3 (TRPV3), TRP Vanilloid 4 (TRPV4), TRP Ankyrin 1 (TRPA1) and TRP Melastatin 8 (TRPM8), more recently TRP Canonical 1, 5, 6 (TRPC1, 5, 6), TRP Melastatin 2 (TRPM2) and TRP Melastatin 3 (TRPM3). These channels are predominantly expressed in C and Aδ nociceptors and transmit noxious thermal, mechanical and chemical sensitivities. TRP channels are modulated by pro-inflammatory mediators, neuropeptides and cytokines. Significant advances have been made targeting these receptors either by antagonists or agonists to treat painful conditions. In this review, we will discuss TRP channels as targets for next generation analgesics and the side effects that may ensue as a result of blocking/activating these receptors, because they are also involved in physiological functions such as release of vasoactive neuropeptides and regulation of vascular tone, maintenance of the body temperature, gastrointestinal motility, urinary bladder control, etc.

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.

The overactive bladder

Urinary urgency and the associated symptoms which comprise overactive bladder are prevalent amongst the general population and adversely affect quality of life. Disease management consists of a sequential series of options starting with behavioural and lifestyle techniques, pharmacological management (antimuscarinics) and, in severe cases, surgical treatment (urinary diversion, neuromodulation, augmentation cystoplasty and detrusor myectomy). There is increasing recognition of pathophysiological mechanisms in the urothelium, interstitial cells and afferent neurons allowing the importance of peripheral integrative interaction to be identified. The hierarchy of the central nervous system control adds additional complexity to understanding the oflower urinary tract function. Some newer methods of treatment include Botulinum toxin A intramural injections, oral beta-3 adrenergic agonists and rho-kinase inhibitors. The lack of a disease generating hypothesis, the lack of animal models for disease and the subjective nature of the central symptom (urgency) still pose considerable theoretical and scientific hurdles that need to be overcome in the treatment of this condition.

Intravesical oxybutynin in the pediatric neurogenic bladder

Pediatric neuropathic bladder dysfunction can cause irreversible renal damage and urinary incontinence. Etiologically, it is usually the consequence of a congenital neural tube defect. The majority of affected children can be successfully managed with the standard medical treatment of clean intermittent catheterization and anticholinergic (typically oxybutynin) medication. A subset of patients experience severe side effects or insufficient suppression of detrusor overactivity on oral oxybutynin. Intravesical instillations offer an effective alternative; this Review considers their indications, administration, safety and efficacy.

Capsaicin (TRPV1 Agonist) therapy for pain relief: farewell or revival?

OBJECTIVE

In this review, we explain our current understanding of the molecular basis for pain relief by capsaicin and other transient receptor potential vanilloid subfamily, member 1 (TRPV1) agonists. We summarize disease-related changes in TRPV1 expression and its implications for therapy and potential adverse effects. Last, we provide an overview of the current clinical uses of topical and injectable TRPV1 agonist preparations in both oncologic and nononcologic populations.

METHOD

Search of MEDLINE and other databases.

RESULTS

The capsaicin receptor TRPV1 is a polymodal nociceptor exhibiting a dynamic threshold of activation that could be lowered under inflammatory conditions. Consistent with this model, TRPV1 knock-out mice are devoid of post-inflammatory thermal hyperalgesia. TRPV1 desensitization of primary sensory neurons is a powerful approach to relieve symptoms of nociceptive behavior in animal models of chronic pain. However, over-the-counter capsaicin creams have shown moderate to poor analgesic efficacy. This is in part related to low dose, poor skin absorption, and compliance factors. Recently developed site-specific capsaicin therapy with high-dose patches and injectable preparations seem to be safe and reportedly provide long-lasting analgesia with rapid onset.

CONCLUSIONS

We argue that TRPV1 agonists and antagonists are not mutually exclusive but rather complimentary pharmacologic approaches for pain relief and we predict a "revival" for capsaicin and other TRPV1 agonists in the clinical management of pain associated with inflammation, metabolic imbalances (eg, diabetes), infections (HIV), and cancer, despite the current focus of the pharmaceutical industry on TRPV1 antagonists.

Evaluation of purinergic mechanism for the treatment of voiding dysfunction: a study in conscious spinal cord-injured rats

BACKGROUND

To investigate the effect of a selective P2X(3-)P2X(2/3) purinergic receptor antagonist (a-317491) on detrusor hyperreflexia in conscious chronic spinal cord-injured female rats.

METHODS

Six chronic spinal cord-transected female Sprague-Dawley rats (290-336 g) were used in this study. Spinal transection at the T8-T9 segmental level was performed using aseptic techniques under halothane anesthesia. Fourteen to 16 weeks after spinal transection, A-317491, a selective P2X(3-)P2X(2/3) purinergic receptor antagonist, was administered intravenously in cystometry studies at increasing doses of 0.03, 0.1, 0.3, 1, 3, 10 and 30 micromol/kg at 40-50 minute intervals. Cystometrograms (CMGs) were performed before and after the administration of each dose of the drug.

RESULTS

The continuous filling of CMGs revealed a large number of small-amplitude (> 8 cmH(2)O), non-voiding contractions (NVCs) (average, 9.7 per voiding cycle) preceding voiding contractions (mean amplitude, 31 cmH(2)O; duration, 2.5 minutes), which occurred at an interval of 539 seconds and at a pressure threshold of 5.7 cmH(2)O. When tested in a range of doses (0.03-30 micromol/kg, intravenous), A-317491 in doses between 1 and 30 micromol/kg significantly (p < 0.05) increased the interval between voids by 25%, reduced the number of NVCs by 42-62%, and increased the pressure threshold for voiding by 53-73%, but did not change the amplitude of the duration of the voiding contractions. The effects of the drug were apparent within 10 minutes following administration.

CONCLUSION

These results indicate that purinergic mechanisms, presumably involving P2X(3) or P2X(2/3) receptors on bladder C-fiber afferent nerves, play an important role in the detrusor hyperreflexia that occurs after spinal cord injury in rats.

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.

TRPs in bladder diseases

This review attempts to provide an overview of the current knowledge of TRP proteins and their possible role in bladder function and disease. At present, there are 28 transient receptor potential (TRP) channels (subdivided into 7 categories or families) which are involved in a number of functions [G.A. Hicks, TRP channels as therapeutic targets: hot property, or time to cool down? Neurogastroenterology and Motility 18, (2006) 590-594., J.D. Levine, N. Alessandri-Haber, TRP channels: targets for the relief of pain, Biochimica et Biophysica Acta 1772, (2007) 989-1003.]. Of those belonging to the group 1 subfamily, a number of TRPV, TRPM and TRPA proteins associated with osmoregulation, thermal, chemical and mechanical signaling mechanisms have been shown to be expressed within the lower urinary tract. Though the biological role of many of these channels in urinary bladder function still remains elusive, TRPV1 is by far the best characterized and is thought to be involved in a number of bladder disorders [A. Szallasi, P.M. Blumberg, Vanilloid (Capsaicin) Receptors and Mechanisms, Pharmacological Reviews 51, (1999) 150-221., I. Nagy, P. Santha, G. Jansco, L. Urban, The role of the vanilloid (capsaicin) receptor (TRPV1) in physiology and pathology, European Journal of Pharmacology 500, (2004) 351-369.].

Clinical usefulness of urodynamic assessment for maintenance of bladder function in patients with spinal cord injury

AIMS

The vast majority of spinal cord lesions cause neurogenic bladder disorders. Detrusor hyperreflexia presents a major risk factor for renal damage in these patients. We evaluated the long-term results of patients with spinal cord injury treated at our institution.

METHODS

Eighty spinal cord injury patients (60 male, 20 female; mean age 29.6 years) with at least one follow-up visit a year for a minimum of five consecutive years, were included in this retrospective analysis. Follow-up included urodynamic evaluation, sonography of the upper and lower urinary tract, urine examination, and evaluation of renal function. Treatment modifications were based on the urodynamic findings.

RESULTS

Mean follow-up was 67.3 months (range 60-103 months). At initial presentation, 51 patients performed intermittent catheterization, 7 had indwelling catheters, 10 utilized reflex voiding, 2 patients presented with a Brindley stimulator, 10 patients used abdominal straining. At the end of our study, no patient had signs of renal damage. To achieve that goal, 8 patients underwent sphincterotomy, 3 received a Brindley stimulator, 3 underwent bladder augmentation, one Kock pouch was performed, and 12 patients were treated with botulinum-A-toxin injections in the detrusor. Twenty-two patients received intravesical anticholinergic therapy. In merely three patients, treatment was not modified during the entire follow-up.

CONCLUSIONS

In the long term, treatment strategy of neurogenic bladder dysfunction in patients with spinal cord injury had to be modified in almost all patients. 18.8% underwent surgery. For protection of the upper urinary tract and maintenance of continence, regular urodynamic follow-up is warranted.

Intravesical glucidic capsaicin versus glucidic solvent in neurogenic detrusor overactivity: a double blind controlled randomized study

AIMS

Many studies report the use of alcoholic capsaicin instillation to treat neurogenic detrusor overactivity (NDO) in spinal cord injured (SCI) and multiple sclerosis (MS) patients. However, poor tolerability due to the irritative effect of the ethanol solvent limits its use. Our study aimed to evaluate the efficacy and tolerability of a new formulation of capsaicin in a glucidic solution in a multicenter clinical trial.

MATERIALS AND METHODS

Thirty-three patients (26MS/7SCI) suffering from urinary incontinence due to refractory NDO were prospectively enrolled in a double-blind placebo controlled study and randomized to capsaicin group (CG, N = 17) or solvent group (SG, N = 16). They respectively received an intravesical instillation of 100 ml capsaicin diluted in glucidic solvent (CG) or glucidic solvent alone (SG). Efficacy (voiding chart, maximum cystometric capacity (MCC)) and tolerability were evaluated on days 0 (D0), 30 and 90.

RESULTS

On D0, groups were homogeneous. On D30, significant improvement of overactive bladder syndrome and an increase in MCC were shown in CG, whereas there were no improvement in SG. No significant improvement was shown on D90 in both groups. There were no significant differences between groups regarding prevalence, duration, or intensity of side effects, except for short duration pubic pain during instillation more often reported in CG (58.8%) than in SG (12.5%) (P < 0.01).

CONCLUSION

This placebo controlled study using glucidic capsaicin confirms its short-term efficacy in NDO patients. Global tolerance of glucidic capsaicin appeared satisfactory. Long-term efficacy and tolerance of repeated glucidic capsaicin instillations need to be evaluated.

New Frontiers in Intravesical Therapies and Drug Delivery

OBJECTIVES

The intravesical route permits site-specific delivery of drugs with a reduced side-effect profile as compared to oral delivery systems, either by avoiding first-pass metabolism or by obtaining a local effect. We investigated mechanisms related to urothelium permeability and new physical and chemical developments in intravesical drug delivery that potentially permit successful treatment of several bladder dysfunction.

METHODS

A literature review.

RESULTS

Pharmacologic agents increasing urothelial permeability and useful for clinical purposes have been described, such as dimethylsulfoxide, protamine sulphate, chitosan, and nystatin. Among physical approaches, electromotive drug administration appears to be more effective than intravesical passive diffusion in delivering drugs through the urothelium into deeper layers of the bladder. Experimental and clinical reports demonstrated that electric current significantly increases the transport of local anaesthetics, mytomicin C, oxybutynin, resiniferatoxin, epinephrine, and dexamethasone. Among new chemical approaches, cell-penetrating peptides posses the ability to translocate macromolecular drugs across membranes of urothelial cells. The therapeutic benefits of sustained delivery afforded by thermosensitive hydrogel, which forms a depot for hydrophilic and hydrophobic drugs, have been demonstrated by delivering anti-inflammatory drugs. Liposomes improve the aqueous solubility of several hydrophobic drugs such as taxol, amphotericin, and capsaicin.

CONCLUSIONS

Electromotive drug administration, new in situ delivery systems, and bioadhesive liposomes may make it possible to extend intravesical therapy and drug administration to many bladder diseases. Research to expand knowledge of the chemical and physical properties of the bladder and processes regulating drug transport across biologic membranes is needed to make this a reality.

Daily intravesical instillation of 1 mg nociceptin/orphanin FQ for the control of neurogenic detrusor overactivity: a multicenter, placebo controlled, randomized exploratory study

PURPOSE

We studied the feasibility, safety and efficacy of daily intravesical instillation of 1 mg of the endogenous peptide nociceptin/orphanin FQ in a selected group of patients who perform clean intermittent self-catheterization for neurogenic detrusor overactivity incontinence.

MATERIALS AND METHODS

A total of 18 patients with neurogenic detrusor overactivity incontinence and on clean intermittent self-catheterization were prospectively randomized to receive 1 mg nociceptin/orphanin FQ in 10 cc saline (9) or placebo (saline) solution (9) at the first morning catheterization for 10 days. All patients completed a voiding diary using a frequency/volume chart according to International Continence Society guidelines, and reported daily incontinence frequency. Mean changes in incontinence episode frequency and voiding diary mean bladder capacity from baseline throughout treatment were the primary outcome variables. Urodynamic parameters (cystomanometric bladder capacity, maximum bladder pressure) were also recorded at baseline and during the study.

RESULTS

The 2 groups were well balanced and all patients completed the study. The urodynamic parameters recorded during the study showed an increase in cystomanometric bladder capacity and a decrease in maximum bladder pressure compared to baseline only in patients assigned to the nociceptin/orphanin FQ group. Mean daily urine leakage episodes during nociceptin/orphanin FQ treatment were 0.94 vs a pretreatment baseline of 2.18 (p < 0.05), while no significant changes were reported in the placebo group (2.06 vs 2.43 baseline). The total mean voiding diary bladder capacity increased from 171 +/- 70 to 294 +/- 107 ml in patients receiving nociceptin/orphanin FQ, while voiding diary mean bladder capacity remained unchanged in patients receiving placebo (from 182 +/- 55 to 178 +/- 23 ml). No significant problems related to feasibility of the procedure as well as significant side effects were reported by patients.

CONCLUSIONS

This study showed that intravesical nociceptin/orphanin FQ but not placebo inhibited the micturition reflex in patients with neurogenic detrusor overactivity incontinence, and demonstrated the clinical efficacy of nociceptin/orphanin FQ during 10 days of treatment. These findings support the use of nociceptin/orphanin FQ peptide receptor agonists as an innovative therapeutic approach for controlling detrusor overactivity incontinence.

The TRPV1 receptor and nociception

The capsaicin receptor TRPV1 is an emerging target for the treatment of pain with a unique expression profile in peripheral nociceptors and the ability to show polymodal activation, TRPV1 is an important integrator of responses to inflammatory mediators. Sensitization of TRPV1 during chronic pain is believed to contribute to the transduction of noxious signaling for normally innocuous stimuli and consequently the search for novel TRPV1 therapeutics is intense. The current understanding of the physiological role the receptor, as well as the potential therapeutic utility and emerging liabilities of TRPV1 modulators are discussed.

Botulinum toxin-type A in the treatment of drug-resistant neurogenic detrusor overactivity secondary to traumatic spinal cord injury

OBJECTIVE

To assess, in a prospective study, whether botulinum toxin-type A (BTX-A) injected into the detrusor muscle, can be used as a day-case treatment for drug-resistant neurogenic detrusor overactivity (NDO) in patients with spinal cord injury (SCI).

PATIENTS AND METHODS

BTX-A (Dysport, Ipsen, Luxembourg; 1000 units) was injected cystoscopically into the detrusor muscle of 37 patients with drug-resistant NDO and SCI, as a day-case procedure. The maximum cystometric capacity (MCC), maximum detrusor pressure (MDP), NDO, continence, and anticholinergic requirement were used as outcome variables. The International Consultation on Incontinence questionnaire (ICIQ) was used to assess the patient's quality of life before and after the BTX-A injection.

RESULTS

The mean follow-up was 7 months. The MCC increased from a mean of 259 to 522 mL, and the MDP decreased from a mean of 54 to 24 cmH2O. Incontinence and NDO were abolished in 82% and 76% patients, respectively. In all, 86% of the patients were able to stop or reduce anticholinergics, with a similar proportion of patients scoring favourably on the ICIQ. The mean duration of improvement was 9 months.

CONCLUSIONS

Injection with BTX-A is an effective day-case treatment that bridges the gap between oral and invasive surgical treatment of drug-resistant NDO in patients with SCI.

Pharmacotherapy for Neurogenic Detrusor Overactivity

Chancellor MB, Anderson RU, Boone TB: Pharmacotherapy for neurogenic detrusor overactivity. Am J Phys Med Rehabil 2006;85:536-545. Patients with neurogenic detrusor overactivity are a heterogeneous group with voiding dysfunction secondary to neurologic injury or disease. The neurogenic detrusor overactivity syndrome, which may include urinary frequency, urgency, and incontinence, frequently contributes to a loss of independence, or even institutionalization. Urodynamic assessment provides the best method of quantifying and classifying neurogenic detrusor overactivity dysfunction in patients with primary diagnoses as diverse as Parkinson's disease, cerebral palsy, multiple sclerosis, spinal cord injury, and spina bifida. For many patients, management of urinary symptoms includes pharmacotherapy with an anticholinergic agent. Several novel approaches to managing neurogenic detrusor overactivity, including intravesical instillation of anticholinergic agents, vanilloids, and neurotoxins, are being investigated. For most patients, however, flexible dosing with an anticholinergic agent, with clean intermittent catheterization when indicated, has been shown to reduce the risks of urologic complications, improve levels of continence, and enhance patient quality of life in both children and adults.

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.