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Szallasi A. Resiniferatoxin: Nature's Precision Medicine to Silence TRPV1-Positive Afferents. Int J Mol Sci 2023; 24:15042. [PMID: 37894723 PMCID: PMC10606200 DOI: 10.3390/ijms242015042] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 09/27/2023] [Accepted: 10/07/2023] [Indexed: 10/29/2023] Open
Abstract
Resiniferatoxin (RTX) is an ultrapotent capsaicin analog with a unique spectrum of pharmacological actions. The therapeutic window of RTX is broad, allowing for the full desensitization of pain perception and neurogenic inflammation without causing unacceptable side effects. Intravesical RTX was shown to restore continence in a subset of patients with idiopathic and neurogenic detrusor overactivity. RTX can also ablate sensory neurons as a "molecular scalpel" to achieve permanent analgesia. This targeted (intrathecal or epidural) RTX therapy holds great promise in cancer pain management. Intra-articular RTX is undergoing clinical trials to treat moderate-to-severe knee pain in patients with osteoarthritis. Similar targeted approaches may be useful in the management of post-operative pain or pain associated with severe burn injuries. The current state of this field is reviewed, from preclinical studies through veterinary medicine to clinical trials.
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Affiliation(s)
- Arpad Szallasi
- Department of Pathology and Experimental Cancer Research, Semmelweis University, 1083 Budapest, Hungary
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Wagner T, Roth-Daniek A, Sell A, England J, Kern KU. Capsaicin 8% patch for peripheral neuropathic pain: review of treatment best practice from 'real-world' clinical experience. Pain Manag 2014; 2:239-50. [PMID: 24654666 DOI: 10.2217/pmt.12.13] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
SUMMARY The capsaicin 8% patch is licensed in Europe for the treatment of peripheral neuropathic pain in nondiabetic adults. In controlled trials it provided pain relief for up to 3 months with a single 30- or 60-min application. In this article, a group of pain specialists from Germany and the UK share their considerable experience of real-world use of the capsaicin 8% patch. This experience comes from treating >200 patients with a variety of neuropathic pain etiologies including postherpetic neuralgia, peripheral neuropathy and cancer-related neuropathy. These patients, a slight majority of whom were female, had experienced neuropathic pain for varied lengths of time (3 months to >15 years) and the majority were receiving concomitant medications for their pain at the time of capsaicin 8% patch treatment. Observations by the group suggest that patients with positive symptoms might respond best to therapy. To optimize response to treatment, the group reports that it is important to achieve good adhesion of the patch to the skin. The experience of the group is that the capsaicin 8% patch is a tolerable treatment and local anesthetic pretreatment may not always be required. Cooling measures used after treatments were found to be the most practical and beneficial means of relieving any treatment-related discomfort. The group observed that transient, clinically important increases in blood pressure owing to treatment-related discomfort are very rare and they have seen no correlation between treatment-related discomfort or erythema and response to treatment. In the real-life clinical setting, response to capsaicin 8% patch treatment may be higher than observed in the clinical trial program. Response to retreatment also appears to be equal to that of the first treatment, even in patients treated for the fifth time. It was also observed that patients receiving capsaicin 8% patch treatment are often able to reduce their intake of concomitant pain medications. Observations from real-life use of the capsaicin 8% patch will help to maximize its therapeutic potential.
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Affiliation(s)
- Till Wagner
- Pain Therapy & Palliative Care Department, Medizinisches Zentrum Städteregion Aachen, Mauerfeldchen 25, 52146 Würselen, Germany
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Kern KU, Nowack W, Poole C. Treatment of neuropathic pain with the capsaicin 8% patch: is pretreatment with lidocaine necessary? Pain Pract 2013; 14:E42-50. [PMID: 24289500 PMCID: PMC4282389 DOI: 10.1111/papr.12143] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 09/16/2013] [Indexed: 11/28/2022]
Abstract
The capsaicin 8% patch can effectively treat neuropathic pain, but application can cause discomfort or a burning sensation. Until March 2013, it was recommended that patients be pretreated with a topical anesthetic, for example lidocaine, before capsaicin patch application. However, speculation existed over the need for pretreatment and its effectiveness in alleviating treatment-associated discomfort. This article compares tolerability to and efficacy of the capsaicin patch in pretreated and non-pretreated patients. All patients received a single capsaicin patch application. Pretreated patients received a lidocaine plaster before and intravenous lidocaine and metamizole infusions during capsaicin patch application. Pain levels, assessed using a Numeric Rating Scale (NRS), were used to determine tolerability and efficacy. All patients (pretreated n = 32; non-pretreated n = 26) completed 100% of the intended capsaicin patch application duration. At the time of capsaicin patch removal, 69% of pretreated and 88% of non-pretreated patients reported an NRS score increase, which returned to baseline by 6 hours post-treatment. There was no significant difference in mean NRS score between patient groups at any time during or after capsaicin patch treatment. Response was similar between patient groups; capsaicin patch treatment provided rapid and significant pain reductions that were sustained over 12 weeks. The same proportion of pretreated and non-pretreated patients reported willingness to receive retreatment with the capsaicin patch. This analysis shows that the capsaicin 8% patch is generally tolerable, and the small discomfort associated with patch application is short-lived. Lidocaine pretreatment does not have a significant effect on tolerability, efficacy, or patient willingness to receive retreatment.
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Affiliation(s)
- Kai-Uwe Kern
- Centre of Pain Medicine and Palliative Care, Wiesbaden, Germany
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4
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Green BG. Regional and Individual Differences in Cutaneous Sensitivity to Chemical Irritants: Capsaicin and Menthol. ACTA ACUST UNITED AC 2008. [DOI: 10.3109/15569529609048881] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Komai H, McDowell TS. Differential effects of bupivacaine and tetracaine on capsaicin-induced currents in dorsal root ganglion neurons. Neurosci Lett 2005; 380:21-5. [PMID: 15854744 PMCID: PMC2046220 DOI: 10.1016/j.neulet.2005.01.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Revised: 12/29/2004] [Accepted: 01/05/2005] [Indexed: 11/25/2022]
Abstract
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.
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Affiliation(s)
| | - Thomas S. McDowell
- * Corresponding author. Tel.: +1 608 265 3186 (Lab)/1 608 263 8698 (Hospital); fax: +1 608 263 0737 (Lab)/1 608 263 0575 (Hospital). E-mail address: (T.S. McDowell)
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6
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Intravesical Capsaicin Versus Resiniferatoxin In Patients With Detrusor Hyperreflexia: A Prospective Randomized Study. J Urol 2002. [DOI: 10.1097/00005392-200204000-00029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Giannantoni A, Di Stasi SM, Stephen RL, Navarra P, Scivoletto G, Mearini E, Porena M. Intravesical Capsaicin Versus Resiniferatoxin In Patients With Detrusor Hyperreflexia: A Prospective Randomized Study. J Urol 2002. [DOI: 10.1016/s0022-5347(05)65183-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Antonella Giannantoni
- From the Department of Urology, University of Perugia, Perugia, Department of Urology “Tor Vergata,” University of Rome, Institute of Pharmacology Catholic University of Rome and IRCCS S. Lucia Rehabilitation Hospital, Rome and Physion Laboratories, Medolla, Italy
| | - Savino M. Di Stasi
- From the Department of Urology, University of Perugia, Perugia, Department of Urology “Tor Vergata,” University of Rome, Institute of Pharmacology Catholic University of Rome and IRCCS S. Lucia Rehabilitation Hospital, Rome and Physion Laboratories, Medolla, Italy
| | - Robert L. Stephen
- From the Department of Urology, University of Perugia, Perugia, Department of Urology “Tor Vergata,” University of Rome, Institute of Pharmacology Catholic University of Rome and IRCCS S. Lucia Rehabilitation Hospital, Rome and Physion Laboratories, Medolla, Italy
| | - Pierluigi Navarra
- From the Department of Urology, University of Perugia, Perugia, Department of Urology “Tor Vergata,” University of Rome, Institute of Pharmacology Catholic University of Rome and IRCCS S. Lucia Rehabilitation Hospital, Rome and Physion Laboratories, Medolla, Italy
| | - Giorgio Scivoletto
- From the Department of Urology, University of Perugia, Perugia, Department of Urology “Tor Vergata,” University of Rome, Institute of Pharmacology Catholic University of Rome and IRCCS S. Lucia Rehabilitation Hospital, Rome and Physion Laboratories, Medolla, Italy
| | - Ettore Mearini
- From the Department of Urology, University of Perugia, Perugia, Department of Urology “Tor Vergata,” University of Rome, Institute of Pharmacology Catholic University of Rome and IRCCS S. Lucia Rehabilitation Hospital, Rome and Physion Laboratories, Medolla, Italy
| | - Massimo Porena
- From the Department of Urology, University of Perugia, Perugia, Department of Urology “Tor Vergata,” University of Rome, Institute of Pharmacology Catholic University of Rome and IRCCS S. Lucia Rehabilitation Hospital, Rome and Physion Laboratories, Medolla, Italy
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Dasgupta P, Chandiramani VA, Beckett A, Scaravilli F, Fowler CJ. The effect of intravesical capsaicin on the suburothelial innervation in patients with detrusor hyper-reflexia. BJU Int 2000; 85:238-45. [PMID: 10671875 DOI: 10.1046/j.1464-410x.2000.00427.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine the effect of intravesical capsaicin on the suburothelial innervation in patients with detrusor hyper-reflexia, in whom a single dose of intravesical capsaicin (1-2 mmol/L) increases the bladder capacity for 3-6 months. PATIENTS AND METHODS Thirteen patients with detrusor hyper-reflexia underwent cystometry and had flexible cystoscopic biopsies taken before and 6 weeks after receiving instillations of intravesical capsaicin (1 mmol/L). Similar biopsies were also obtained from a control group of 12 neurologically normal patients with microscopic haematuria and normal bladders. Frozen sections were stained using antibodies to S100 and PGP 9.5. Using computerized analysis, the mean nerve density scores were expressed as nerves/mm2 for S100-positive structures and 'red%' and 'red in frame' for PGP 9.5. RESULTS The mean (SEM) functional bladder capacity increased from 193.2 (28.17) mL before to 396.3 (41.96) mL at 6 weeks after treatment with capsaicin, in nine of the 13 patients. The mean nerve density of S100-positive structures in the control group was 83 (3.18) nerves/mm2. In hyper-reflexic patients who responded to capsaicin by improved bladder capacity, the mean nerve density of S100-positive structures was reduced from 100 (12.2) before to 66 (9.4) nerves/mm2 6 weeks after treatment. In those who did not respond to capsaicin there was no significant difference in these scores. Similarly the 'red%' and 'red in frame' reduced from 3.41 (1.06) to 1.15 (0.32) and 824.7 (246.3) to 297.9 (83.5) units, respectively, before and 6 weeks after capsaicin treatment. The difference in those not responding was not significant. CONCLUSIONS Intravesical capsaicin causes a reduction in suburothelial nerve densities in the bladder of patients with detrusor hyper-reflexia. This may explain its prolonged beneficial effect in these patients.
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Affiliation(s)
- P Dasgupta
- Departments of Uro-Neurology and Neuropathology, Institute of Neurology, Queen Square, London, UK
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Avelino A, Cruz F, Coimbra A. Intravesical resiniferatoxin desensitizes rat bladder sensory fibres without causing intense noxious excitation. A c-fos study. Eur J Pharmacol 1999; 378:17-22. [PMID: 10478560 DOI: 10.1016/s0014-2999(99)00451-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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.
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Affiliation(s)
- A Avelino
- Institute of Histology and Embryology, Faculty of Medicine of Oporto, IBMC of University of Oporto, Porto, Portugal
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Abstract
Pains arising from the viscera constitute a large portion of clinically treated pains. They are characterized by poor localization; immobility with tonic increases in muscle tone; and vigorous but nonspecific changes in autonomic function, such as changes in respiration, heart rate, and blood pressure. Tissue-damaging stimuli do not reliably produce visceral pain, so the study of visceral nociception in nonhuman animals requires identification of appropriate stimuli and responses. This article defines "noxious" visceral stimuli as those that produce pain in humans, result in aversive behaviors in animals, and evoke responses that are inhibited by manipulations known to be analgesic in humans. To be valid, the measured responses must be reliable, inhibited by known analgesics, and not inhibited by nonanalgesics. Using these criteria as measures of validity, the author examined several visceral pain models. The writhing test (application of intraperitoneal irritants) failed to meet these criteria; however, responses to small bowel distension, colonic-rectal distension, artificial ureteral calculosis, urinary tract distension, and the intravesical application of irritants met most, if not all, of the criteria. Other models, such as responses to biliary system distension, to reproductive organ stimulation, to the focal application of algesic agents onto various viscera, and to ischemic stimuli, met some of these criteria. This information should assist readers in decisions related to the use of visceral pain models.
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Affiliation(s)
- T.J. Ness
- Department of Anesthesiology, University of Alabama at Birmingham, Alabama, USA
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11
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Cruz F. 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. Int Urogynecol J 1998; 9:214-20. [PMID: 9795827 DOI: 10.1007/bf01901607] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
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.
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Affiliation(s)
- F Cruz
- Department of Urology, Hospital São João, Oporto, Portugal
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Dasgupta P, Fowler CJ, Stephen RL. Electromotive drug administration of lidocaine to anesthetize the bladder before intravesical capsaicin. J Urol 1998; 159:1857-61. [PMID: 9598475 DOI: 10.1016/s0022-5347(01)63176-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
PURPOSE The discomfort caused by intravesical capsaicin during instillation may restrict its use in some patients. We studied the effectiveness of using electromotive drug administration (EMDA) of lidocaine to anesthetize the bladder before capsaicin. MATERIALS AND METHODS EMDA of lidocaine and epinephrine was performed in 8 patients with detrusor hyperreflexia using catheters, electrodes and an electrical current generator (20 mA., 15 minutes) followed immediately by intravesical capsaicin (2 mmol./l.) for 30 minutes under urodynamic monitoring. The patients scored suprapubic pain at 5 minutes and at the end of the capsaicin instillations on a scale of 0 to 10. Of the 8 patients 5 had had previous capsaicin treatments and the scores were compared to previous scores when intravesical lidocaine without EMDA had been used as local anesthesia before capsaicin. RESULTS The pain scores during capsaicin instillations after EMDA of lidocaine were much lower than those during capsaicin instillations after lidocaine alone. EMDA virtually eliminated the hyperreflexic contractions of the bladder occurring during capsaicin instillations, thus reducing the risk of urethral leakage, and prevented autonomic dysreflexia that had previously occurred in 1 patient. CONCLUSIONS EMDA of lidocaine is an effective means of reducing pain during subsequent intravesical capsaicin, which makes the use of capsaicin in the treatment of detrusor hyperreflexia more acceptable.
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Affiliation(s)
- P Dasgupta
- Uro-Neurology Department, Institute of Neurology, London, England
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ELECTROMOTIVE DRUG ADMINISTRATION OF LIDOCAINE TO ANESTHETIZE THE BLADDER BEFORE INTRAVESICAL CAPSAICIN. J Urol 1998. [DOI: 10.1097/00005392-199806000-00019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Avelino A, Cruz F, Coimbra A. Lidocaine prevents noxious excitation of bladder afferents induced by intravesical capsaicin without interfering with the ensuing sensory desensitization: an experimental study in the rat. J Urol 1998; 159:567-70. [PMID: 9649293 DOI: 10.1016/s0022-5347(01)63985-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
PURPOSE The effects of the local anesthetic lidocaine on the noxious excitation and subsequent desensitization of bladder sensory fibers, produced by intravesical capsaicin, were evaluated through c-fos activation in the spinal cord. MATERIALS AND METHODS Noxious excitation was demonstrated by counting Fos-immunoreactive (IR) cells occurring in the rat spinal cord 2 hours after intravesical administration of 1 mM. capsaicin, preceded or not by 2% lidocaine. Desensitization was studied by comparing the number of Fos-IR cells induced by 1% acetic acid in rats treated 24 hours before with 1 mM. intravesical capsaicin preceded or not by 2% lidocaine. RESULTS Lidocaine instilled previously markedly reduced the number of Fos-IR spinal cells responding to capsaicin-induced bladder afferent excitation. Numbers of Fos-IR cells induced by acetic acid instillation in bladders desensitized by capsaicin administrated 24 hours before were not changed by lidocaine application prior to capsaicin. CONCLUSIONS These findings suggest that local anesthetic pretreatment of the bladder with lidocaine reduces the capsaicin-induced noxious excitation of the sensory fibers without decreasing their subsequent desensitization.
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Affiliation(s)
- A Avelino
- Institute of Histology and Embryology, Faculty of Medicine of Porto, IBMC of University of Porto, Portugal
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De Ridder D, Chandiramani V, Dasgupta P, Van Poppel H, Baert L, Fowler CJ. Intravesical capsaicin as a treatment for refractory detrusor hyperreflexia: a dual center study with long-term followup. J Urol 1997; 158:2087-92. [PMID: 9366318 DOI: 10.1016/s0022-5347(01)68162-x] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
PURPOSE We described the long-term outcome of intravesical capsaicin instillations in patients with urinary incontinence and compared its efficacy in 2 similar populations of patients with multiple sclerosis in a dual center study. MATERIALS AND METHODS During 5 years 79 patients with intractable urinary incontinence have been treated with intravesical capsaicin. The majority of patients had spinal cord disease due to multiple sclerosis but 4 were neurologically normal. Cystometry was performed before and 4 to 6 weeks after intravesical instillation of 1 to 2 mmol./l. of capsaicin in 30% ethanol in saline. Instillations of vehicle (30% ethanol in saline) alone were carried out in 5 patients. RESULTS In patients with phasic detrusor hyperreflexia complete continence was achieved in 44%, satisfactory improvement occurred in 36% and treatment failed in 20%. Clinical benefit from a single instillation lasted 3 to 6 months and was repeated in some patients with similar improvement. Capsaicin was ineffective in patients with poor bladder compliance and in neurologically normal patients with sensory urgency and detrusor instability. There was no clinical or urodynamic improvement in patients treated with vehicle alone. There have been no long-term complications. CONCLUSIONS Our study shows that repeated instillations of intravesical capsaicin are effective in treatment of patients with detrusor hyperreflexia due to spinal cord disease and that effectiveness of the treatment persists at least 3 to 5 years.
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Affiliation(s)
- D De Ridder
- Department of Uro-Neurology, National Hospital for Neurology and Neurosurgery, London, United Kingdom
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16
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Abstract
Topical desensitization of the tongue was assessed during multiple bouts of exposure to capsaicin. In the first experiment subjects rated perceived irritation as 30 capsaicin stimuli (33 microM) were applied to the tongue tip in three blocks of 10, with 15 min breaks between blocks. Significant desensitization was measured at the beginning of the second and third blocks within each session. However, as stimulation continued within those blocks sensations of irritation grew toward undesensitized levels ('stimulus-induced recovery' (SIR)). Desensitization did not extend across days. The second experiment employed a 10-fold higher concentration of capsaicin (330 microM) to determine if SIR was limited to low levels of desensitization. SIR occurred as before within sessions, and the higher concentration produced desensitization across days that also exhibited recovery during the first block of stimuli on days 2 and 3. The third experiment included piperine, zingerone and citric acid as stimuli to determine if SIR was specific to capsaicin. Piperine produced SIR under conditions of both self- and cross-desensitization with capsaicin, whereas recovery failed to materialize with zingerone. Citric acid was not significantly cross-desensitized by capsaicin, so recovery could not be measured. Overall the results demonstrate that desensitization of the tongue produced by either capsaicin or piperine can be temporarily reversed if stimulation with either chemical is resumed for only a few minutes. The implications these findings may have for hypotheses about the mechanisms of capsaicin desensitization and sensitization as well as for clinical applications of capsaicin as a topical analgesic are discussed.
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Affiliation(s)
- B G Green
- Monell Chemical Senses Center, Philadelphia, PA 19104-3308, USA
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Craft RM, Cohen SM, Porreca F. Long-lasting desensitization of bladder afferents following intravesical resiniferatoxin and capsaicin in the rat. Pain 1995; 61:317-323. [PMID: 7659443 DOI: 10.1016/0304-3959(94)00193-i] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The present study was conducted to determine whether long-lasting desensitization of bladder afferents could be achieved using a single local application of the capsaicin (CAP)-like irritant resiniferatoxin (RTX), and to compare the effects of RTX and CAP on behavioral and histological endpoints. While rats were anesthetized, vehicle (VEH), RTX (10-100 nmol) or CAP (10-100 mumol) was instilled in the bladder (intravesical, i.ves.) via a cannula surgically implanted into the bladder dome. Beginning 1 week after treatment, once per week for 4 weeks, rats were tested behaviorally for desensitization to i.ves. RTX (10 nmol) using the abdominal lick test. Rats pretreated with low doses of RTX and CAP were partially desensitized at week 1; desensitization diminished over weeks 2-3. In contrast, rats pretreated with high doses of RTX or CAP were more completely desensitized at week 1, and desensitization did not diminish by week 4. Separate groups of rats tested 8 weeks after treatment showed substantial recovery. Rats pretreated with RTX but tested only with VEH for the first 3 weeks showed desensitization at week 4 approximately equivalent to that of RTX-treated rats tested with RTX every week. Sensitivity of corneal afferents to RTX (1.0 microgram/ml) at week 4 was not different between VEH- and RTX- or CAP-treated rats. Gross and histological examination of bladder tissue indicated that both RTX and CAP produced inflammation, which diminished in a dose- and time-dependent manner (1-8 weeks post-treatment).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- R M Craft
- Department of Pharmacology, University of Arizona Health Sciences Center, Tucson, AZ 85724 USA Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE 68198 USA
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Craft RM, Porreca F. Temporal parameters of desensitization to intravesical resiniferatoxin in the rat. Physiol Behav 1994; 56:479-85. [PMID: 7972397 DOI: 10.1016/0031-9384(94)90290-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Temporal factors affecting desensitization of bladder sensory afferents to the capsaicin-like irritant resiniferatoxin (RTX) were studied, to determine optimal treatment parameters for clinical application of such substances. Four days after implantation of a chronic cannula into the bladder dome, vehicle or RTX (0.1-10 nmol) was injected into the bladders of awake, freely moving rats four times at 60-min intervals for exposure durations of 5, 15, or 45 min, or at intervals of 15, 60, or 120 min (duration 5 min). The first RTX injection dose-dependently increased time spent engaged in abdominal licking. Regardless of exposure interval and duration, time spent licking increased to a lesser extent with each subsequent injection, indicating desensitization of sensory afferents. Magnitude and duration of desensitization were dose dependent for all exposure regimens, and there were few differences between groups. Desensitization at 24 h was also greater in rats exposed four times compared to rats exposed once. Following four exposures to RTX, nearly complete recovery occurred within 7-14 days, in a dose-dependent manner. Thus, magnitude and duration of desensitization to locally administered RTX depend primarily on dose and number of exposures to RTX; duration of exposure and interval between exposures within the ranges studied were less important determinants.
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Affiliation(s)
- R M Craft
- Department of Pharmacology, University of Arizona Health Sciences Center, Tucson 85724
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