Lidocaine prevents noxious excitation of bladder afferents induced by intravesical capsaicin without interfering with the ensuing sensory desensitization: an experimental study in the rat

Epidural sustained release ropivacaine prolongs anti-allodynia and anti-hyperalgesia in developing and established neuropathic pain

Ropivacaine is a local anesthetic widely used for regional anesthesia and epidural analgesia, but its relatively short duration limits its clinical use. A novel sustained release lipid formulation of ropivacaine has been recently developed to prolong its duration. We examined the epidural anti-hypersensitivity and preemptive effects of ropivacaine in mesylate injection and sustained release suspension forms in a rat model of neuropathy produced by peripheral nerve injury. Epidural administration of ropivacaine mesylate injection specifically blocked mechanical allodynia and thermal hyperalgesia by approximately 50% with a biological half-effective duration of approximately 3 hrs. The equivalent dose of ropivacaine free-base in sustained release suspension significantly prolonged the duration of anti-allodynia and anti-hyperalgesia by approximately 2 times. Multiple daily epidural injections of ropivacaine in both the mesylate injection and sustained-release suspension forms did not induce tolerance or potentiation to anti-allodynia or anti-hyperalgesia. Moreover, the single or multiple daily administration of ropivacaine mesylate injection before surgery in particular, markedly blocked the initiation and development of neuropathic pain, increasing the biological half-effective duration from less than 4 hrs up to 1 or 2 days. The single and multiple daily epidural injection of ropivacaine sustained release suspension further delayed the biological half-lives to 2 and 3 days, respectively. Our results indicate that the epidural administration of ropivacaine effectively blocks neuropathic pain without the induction of analgesic tolerance, and significantly delays the development of neuropathy produced by peripheral nerve injury. Epidural ropivacaine sustained release suspension produces much longer blockade effects of mechanical allodynia and heat hyperalgesia, and more significantly delays the development of neuropathic pain.

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.

Differential effects of bupivacaine and tetracaine on capsaicin-induced currents in dorsal root ganglion neurons

Capsaicin opens the TRPV1 channel, a cation channel that depolarizes and activates nociceptive neurons. Following this initial activation, neurons become desensitized to subsequent applications of capsaicin as well as to other noxious stimuli, a phenomenon attributed primarily to the entry of Ca2+ ions through the open TRPV1 channel. This ability of capsaicin to desensitize nociceptors has led to its use as an analgesic in the treatment of a variety of chronic pain states. Because treatment with capsaicin is initially quite painful, local anesthetics are sometimes used to block axonal conduction in nociceptive neurons and thus minimize pain. However, local anesthetics might also block TRPV1 and prevent the Ca2+ entry required for capsaicin-induced desensitization. We have studied the direct effect of local anesthetics on currents induced by capsaicin (1 microM) in acutely isolated rat dorsal root ganglion neurons using the whole cell patch clamp technique. At the highest concentration tested (1 mM), bupivacaine only moderately inhibited the capsaicin-induced current to 55 +/- 27% of control (mean +/- S.D.; n=12, p<0.01). Tetracaine (1 mM), on the other hand, enhanced the capsaicin-induced current to 151 +/- 34% of control (mean +/- S.D.; n=7, p<0.01). These results show that local anesthetics can be used to prevent the initial pain induced by application of capsaicin without abolishing, and perhaps even enhancing, its desensitizing actions.

Management of post-operative bladder spasm

OBJECTIVE

Pain management following bladder surgery in children is often complicated by bladder spasm. The overall severity of spasm can be reduced with opioids, anticholinergic medication and sedatives, although breakthrough spasms often occur. At the Royal Children's Hospital, Melbourne, intravesical bupivacaine has been used to manage postoperative bladder spasm to good effect. The administration of intravesical bupivacaine is analysed in this prospective audit of locally applied intravesical anaesthetic and compared with other methods.

METHOD

From February to August 2003, histories of 58 patients who had intravesical bupivacaine were studied and compared with six other methods of management of postoperative bladder spasm.

CONCLUSION

Data showed that epidural anaesthesia was the most effective treatment of pain, with a pain score reduction of 6.6, compared with a reduction of 6.1 with intravesical bupivacaine, and 4.5 using intravenous morphine. However, intravesical bupivacaine was the most effective method for the relief of bladder spasm.

Intravesical therapy options for neurogenic detrusor overactivity

STUDY DESIGN

Review article.

SETTING

Neuro-Urology, Spinal Cord Injury Center, Balgrist University Hospital, Zurich, Switzerland.

OBJECTIVES

This review considers intravesical treatment options of neurogenic detrusor overactivity and discusses the underlying mechanism of action, clinical safety and efficacy, and the future trends.

METHODS

The available literature was reviewed using medline services.

RESULTS

Oral anticholinergic drugs are widely used to treat detrusor overactivity, but they are ineffective in some patients or cause systemic side effects such as blurred vision or dry mouth. As an alternative, topical therapy strategies have been suggested to achieve a profound inhibition of the overactive detrusor and to avoid high systemic drug levels. Currently available intravesical treatment options either act on the afferent arc of the reflex such as local anaesthetics or vanilloids or on the efferent cholinergic transmission to the detrusor muscle such as intravesical oxybutynin or botulinum toxin. Although an established and effective therapy, intravesical oxybutynin is not widely used. Evidence for clinical significance of intravesical atropine and local anaesthetic is missing. Intravesical capsaicin has been shown to improve clinical and urodynamic parameters, but cause pain in some patients. The intravesical instillation of resiniferatoxin and the injection of botulinum-A toxin into the detrusor muscle are promising new options; however, randomised placebo-controlled studies to prove their safety and efficacy are still missing.

CONCLUSION

Intravesical treatment strategies in patients with neurogenic detrusor overactivity may provide alternatives to established therapies such as oral anticholinergics. The selectivity of the intravesical treatment and the reduction or even the absence of side effects are major advantages of this topical approach.

Change of vanilloid receptor 1 following neuromodulation in rats with spinal cord injury

BACKGROUND

Neuromodulation has been used to treat voiding dysfunction caused by spinal cord injury (SCI). However, the underlying mechanism of this technique is not well understood. Recently, vanilloid receptor 1 (VR1) has been recognized as a capsaicin receptor and an agent for noxious stimuli. The purposes of this study were to evaluate whether development of bladder hyperreflexia after SCI involves VR1 upregulation and whether VR1 is involved in the process of neuromodulation.

MATERIALS AND METHODS

Sprague-Dawley rats (n = 20) were divided into five groups: sham control (n = 4); 3 days after SCI (n = 4); 7 days after SCI (n = 4); 14 days after SCI (n = 4), and 14 days after SCI with neurostimulation (n = 4). Bilateral electrode wires were implanted into S1 dorsal foramina and electrical stimulation was performed 8 h/day for 2 weeks. Spinal segments of L6, S1, and dorsal root ganglia were removed and cut into sections. The intensity of VR1 staining was evaluated by image analysis.

RESULTS

VR1-positive staining was confined to the superficial dorsal horn of the spinal cord. The staining was weak in the sham group (1/luminosity: 0.0050 +/- 0.0006), but the staining intensity was significantly increased in three SCI groups (3 days, 7 days, and 14 days) when compared with that in the sham group (P < 0.05). After neuromodulation, the staining intensity was reduced.

CONCLUSIONS

VR1 expression in the spinal cord is up-regulated after SCI. Sacral nerve root stimulation can down-regulate the VR1 expression.

Vanilloid receptor and detrusor instability

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

[Reiterated intravesical instillation of capsaicin in neurogenic detrusor hyperreflexia: a 5-years experience of 100 instillations]

INTRODUCTION

Capsaicin is a topic and specific C-fiber afferent neurotoxic. After spinal-cord injury, C-fiber afferent proliferate in the bladder mucosae and are involving in detrusor hyperreflexia

AIM OF THE STUDY

To investigate middle-term efficacy and tolerance of intravesical instillation of capsaïcin in spinal-cord injured patients presenting severe urinary incontinence refractory to usual therapy due to detrusor hyperreflexia.

METHODS

Thirty patients receveid a first intravesical instillation of 1mMol/L Capsaïcin solution in 30% alcohol. The efficacy (voiding diary, pads, quality of life, maximum cystometric capacity, maximum detrusor pressure, first and normal desire to void) and tolerance were evaluated before, 1 month and 3 months after each instillation, completed by anual cystoscopy. In patients who responded favorably to this instillation, repeated instillations were proposed when symptoms recurred.

RESULTS

25 patients (83.3%) were improved after the initial instillation (decrease of incontinence-frequency-urgency, best quality of life, rise on maximal cystometric capacity), since the 15(th) day and for 3.2 months. 76 reiterative instillations were performed in 22 patients (2 to 9 instillations per patient). 91.2% of them remained successfull, during an average period of 4.2 months. It does not appear loss of benefits after iterative instillations. Transient and moderate adverse effects followed 86% and 79% of the first and reiterated instillation (exacerbation of incontinence, supra-pubic pain). Two patients have presented a begnin and transient inflammatory cystitis after reiterated instillation.

DISCUSSION-CONCLUSION

Intravesical instillation of capsaïcin are an effective treatment for incontinence and associated symptoms caused by neurogenic detrusor hyperactivity. Propositions to improve immediate tolerance are debated.

The effects of intravesical lidocaine on bladder dynamics of children with myelomeningocele

PURPOSE

Other studies have suggested that intravesical lidocaine may temporarily improve bladder dynamics but details of these effects and their application to children have not been examined. We evaluated the effects of intravesical lidocaine on bladder urodynamics of children with myelomeningocele and tried to correlate these effects with subsequent clinical response to oral oxybutynin.

MATERIALS AND METHODS

Charts of children with myelomeningocele who had undergone urodynamic examinations from 1992 to 1998 were reviewed retrospectively. In children with uninhibited contractions or poor compliance 150 to 300 mg. lidocaine were instilled for 8 minutes and cystometry was repeated. Changes in bladder capacity and compliance, number of uninhibited contractions and bladder volume at which pressure of 40 cm. H2O was reached were recorded before and after the lidocaine instillation. Clinical response to subsequent treatment with oral oxybutynin was assessed from chart review.

RESULTS

A total of 48 urodynamic studies in 22 girls and 20 boys with a mean age plus or minus standard deviation of 8.3 +/- 5.7 years and myelomeningocele were evaluable. After instillation of lidocaine, urodynamics showed increased bladder capacity in 70.8% of studies (34 of 48), with an average increase in volume of 66% (p <0.05). No change or decreased bladder capacity occurred in 29.2% of studies. Bladder compliance improved in 61.7% of the studies (29 of 47, p <0.05) and worsened in 38.3%. Bladder volume at which the pressure of 40 cm. H2O was reached increased in 77.8% of studies (14 of 18, p <0.05). After lidocaine the number of uninhibited contractions decreased by 3.2 in 56.8% of studies (21 of 37, p <0.05). Correlation of lidocaine induced changes in bladder capacity, compliance and number of uninhibited contractions with improvement on oral oxybutynin was 70.6%, 64.3% and 66.7%, respectively.

CONCLUSIONS

Intravesical lidocaine can improve bladder capacity and compliance and decrease the number of uninhibited contractions in many children with neurogenic bladder caused by myelomeningocele. These observations suggest that intravesical lidocaine has effects on the neurogenic bladder that improve bladder dynamics. Although intravesical lidocaine testing may not reliably predict clinical response to oral oxybutynin at the prescribed dosages, a possible therapeutic role for intravesical lidocaine or similar agents should be explored further.

The effects of intravesical lidocaine on bladder dynamics of children with myelomeningocele

PURPOSE

Other studies have suggested that intravesical lidocaine may temporarily improve bladder dynamics but details of these effects and their application to children have not been examined. We evaluated the effects of intravesical lidocaine on bladder urodynamics of children with myelomeningocele and tried to correlate these effects with subsequent clinical response to oral oxybutynin.

MATERIALS AND METHODS

Charts of children with myelomeningocele who had undergone urodynamic examinations from 1992 to 1998 were reviewed retrospectively. In children with uninhibited contractions or poor compliance 150 to 300 mg. lidocaine were instilled for 8 minutes and cystometry was repeated. Changes in bladder capacity and compliance, number of uninhibited contractions and bladder volume at which pressure of 40 cm. H2O was reached were recorded before and after the lidocaine instillation. Clinical response to subsequent treatment with oral oxybutynin was assessed from chart review.

RESULTS

A total of 48 urodynamic studies in 22 girls and 20 boys with a mean age plus or minus standard deviation of 8.3 +/- 5.7 years and myelomeningocele were evaluable. After instillation of lidocaine, urodynamics showed increased bladder capacity in 70.8% of studies (34 of 48), with an average increase in volume of 66% (p <0.05). No change or decreased bladder capacity occurred in 29.2% of studies. Bladder compliance improved in 61.7% of the studies (29 of 47, p <0.05) and worsened in 38.3%. Bladder volume at which the pressure of 40 cm. H2O was reached increased in 77.8% of studies (14 of 18, p <0.05). After lidocaine the number of uninhibited contractions decreased by 3.2 in 56.8% of studies (21 of 37, p <0.05). Correlation of lidocaine induced changes in bladder capacity, compliance and number of uninhibited contractions with improvement on oral oxybutynin was 70.6%, 64.3% and 66.7%, respectively.

CONCLUSIONS

Intravesical lidocaine can improve bladder capacity and compliance and decrease the number of uninhibited contractions in many children with neurogenic bladder caused by myelomeningocele. These observations suggest that intravesical lidocaine has effects on the neurogenic bladder that improve bladder dynamics. Although intravesical lidocaine testing may not reliably predict clinical response to oral oxybutynin at the prescribed dosages, a possible therapeutic role for intravesical lidocaine or similar agents should be explored further.

Neuromodulation reduces urinary frequency in rats with hydrochloric acid-induced cystitis

OBJECTIVE

To evaluate the effect of sacral neuromodulation on interstitial cystitis (IC) and determine the underlying mechanism of neuromodulation in the treatment of IC. Materials and methods Twenty Sprague-Dawley rats (body weight 220-250 g) were randomly divided into four equal groups; normal controls, a sham treatment (IC induced by 0.4 mol/L HCl, + saline), a second sham treatment (HCl-induced IC + acetic acid) and a stimulated group (HCl-induced IC + acetic acid, with electrical stimulation). In the last group bilateral electrodes were implanted into the S1 dorsal foramina and electrical stimulation applied for 8 h/day for 3 weeks. Acetic acid was instilled into the bladder to induce c-fos expression. After 3 weeks the rats were perfused with 4% paraformaldehyde, spinal segments dissected out and an immunocytochemical method used to stain the segments for fos protein encoded byc-fos.

RESULTS

The mean (SEM) micturition frequency (voids/17 h) in the sham groups increased from 10.8 (2.7) to 23.4 (3.4) 3 weeks after the intravesical instillation of HCl. The micturition frequency in the stimulated group, at 16.2 (2.7), was significantly less than in the sham group (P = 0.04) after electrical stimulation for 3 weeks. There was no significant difference in the mean (SEM) number of fos-positive neurones in the L6 spinal cord segment between the stimulated and the sham + acetic acid group, at 43.6 (9.4) and 35.8 (7.8) cells/section, respectively (P = 0.32).

CONCLUSIONS

In rats with HCl-induced cystitis, electrical stimulation reduced the micturition frequency, but not by inhibiting afferent c-fibre activity.

Intravesical resiniferatoxin desensitizes rat bladder sensory fibres without causing intense noxious excitation. A c-fos study

In this study the desensitizing power of increasing concentrations of resiniferatoxin applied topically to the bladder mucosa, and the irritating properties of the most effective desensitizing dose, were determined with the aid of the spinal expression of the proto-oncogene c-fos. Desensitization was assessed by the decrease in the number of Fos-immunoreactive spinal neurons induced by the intravesical instillation of 1% acetic acid, when the latter was preceded by resiniferatoxin in concentrations between 1 and 1000 nM. Irritation, as shown by the noxious excitation of vesical sensory innervation, was measured by the c-fos response evoked by a single application of resiniferatoxin. As to the desensitizing power, resiniferatoxin produced a dose-dependent effect with a maximum at 100 nM, which decreased Fos-immunoreactive cell numbers to less than 10% of controls. No further decrease of c-fos activation occurred at 1000 nM. As to the irritating power, the saturation dose of resiniferatoxin (100 nM) produced a very weak c-fos activation in lumbosacral spinal cord segments. These data show that in an effective desensitizing concentration, resiniferatoxin is virtually devoid of nociceptive effects, in agreement with current clinical observations.

Desensitization of bladder sensory fibers by intravesical capsaicin or capsaicin analogs. A new strategy for treatment of urge incontinence in patients with spinal detrusor hyperreflexia or bladder hypersensitivity disorders

Recent experimental studies have identified a category of unmyelinated type C bladder afferent fibers in the pelvic nerves which are extremely sensitive to capsaicin. Sensory input conveyed by these fibers triggers a spinal reflex which, in chronic spinalized animals, facilitates and controls micturition. In addition, bladder C fibers were also shown to have a role in bladder pain perception. In humans capsaicin-sensitive afferent fibers also innervate the bladder and contribute to the reflexogenic control of the detrusor muscle and to bladder pain perception. Desensitization of such fibers by intravesical administration of capsaicin, presumably by blocking sensory transmission, has been shown to reduce involuntary micturition and to increase bladder capacity in patients with detrusor hyperreflexia of spinal origin, and to reduce the intensity of bladder pain in patients with bladder hypersensitivity. Very recently, resiniferatoxin, an ultrapotent capsaicin analog, was shown to have a similar clinical effect in this subset of patients. However, unlike capsaicin, resiniferatoxin did not evoke acute irritative urinary symptoms during bladder instillation.