Effects of capsaicin on swallowing function in stroke patients with dysphagia: A randomized controlled trial.

BACKGROUND/AIMS: Dysphagia is a common complication after acute stroke. While there are several innovative treatments being tested to improve the swallowing function of stroke patients with dysphagia, our aim is to explore the use of readily available natural capsaicin in stroke patients with dysphagia. STUDY DESIGN: A randomized, double-blind study. METHODS: Sixty-nine hospitalized stroke patients were enrolled in this study. The capsaicin intervention group received thermal tactile stimulation with supplementation of natural capsaicin and additional nectar viscosity boluses. The control group received stimulation and boluses with placebo. Swallowing function was evaluated before and after the 3-week treatment, using Volume-Viscosity Swallow Test, Eating Assessment Tool, Standardized Swallowing Assessment, and Water Swallow Test. RESULTS: The score decreases in the Eating Assessment Tool and Standardized Swallowing Assessment of the capsaicin intervention group were significantly greater than that of the placebo control group (P < .01). Among the 60 patients, the capsaicin intervention group exhibited effectiveness in a higher number of patients (n = 27, 90%) than the placebo group (n = 9, 30%, P < .001). CONCLUSIONS: Regular use of natural capsaicin could promote the recovery of swallow function in stroke patients with dysphagia. The ample availability of natural capsaicin could provide a low cost, easily accessible, and safe alternative method to address dysphagia in stoke patients.

Baby Shampoo to Relieve the Discomfort of Tear Gas and Pepper Spray Exposure: A Randomized Controlled Trial.

INTRODUCTION: Oleoresin capsicum (OC) or pepper spray, and tear gas (CS) are used by police and the military and produce severe discomfort. Some have proposed that washing with baby shampoo helps reduce this discomfort. METHODS: We conducted a prospective, randomized, controlled study to determine if baby shampoo is effective in reducing the severity and duration of these effects. Study subjects included volunteers undergoing OC or CS exposure as part of their police or military training. After standardized exposure to OC or CS all subjects were allowed to irrigate their eyes and skin ad lib with water. Those randomized to the intervention group were provided with baby shampoo for application to their head, neck, and face. Participants rated their subjective discomfort in two domains on a scale of 0-10 at 0, 3, 5, 10, and 15 minutes. We performed statistical analysis using a two-tailed Mann-Whitney Test. RESULTS: There were 58 participants. Of 40 subjects in the OC arm of the study, there were no significant differences in the ocular or respiratory discomfort at any of the time points between control (n=19) and intervention (n=21) groups. Of 18 subjects in the CS arm, there were no significant differences in the ocular or skin discomfort at any of the time points between control (n=8) and intervention (n=10) groups. CONCLUSION: Irrigation with water and baby shampoo provides no better relief from OC- or CS-induced discomfort than irrigation with water alone.

Therapeutic Applications of Capsaicin in Upper Airways.

BACKGROUND: Capsaicin (8-methyl-N-vanillyl-6-nonenamide) is the substance responsible of the irritation caused by the contact of chili peppers with the skin or mucous membranes. This protoalkaloid acts by stimulating the transient receptor potential cation channel subfamily V member 1 (TRPV1), which is mainly expressed by nociceptive fibers of peripheral sensory neurons, but is also present in the central nervous system, and in some non-neuronal cells. Following the initial, intense neuronal excitation, a brief refractory period occurs. However, repeated and massive exposures to capsaicin can impair nociceptive fiber function for weeks or months. During this lapse of time, disorders related to the hyperreactivity of peripheral nociceptors are abolished or greatly reduced. Capsaicin has been utilized to treat several diseases of upper airways. OBJECTIVE: The objective of this review was to report the latest findings on the use of Capsaicin in the treatment of upper airway diseases. RESULTS: Capsaicin effectiveness has been proved in non allergic rhinitis. Some studies suggest that this substance may be also effective in nasal polyposis and in the burning mouth syndrome. No clear evidence has been obtained about its use in allergic rhinitis. CONCLUSION: To date, the use of capsaicin to treat upper airway diseases is still limited in clinical practice. This may originate by the lack of strong, conclusive evidences of its effectiveness, by the variety of therapeutic schemes used in literature, and finally by the unpleasant effects of the exposure to capsaicin, which are only partly relieved by the pretreatment with local anesthetics.

Capsaicin 8% patch repeat treatment plus standard of care (SOC) versus SOC alone in painful diabetic peripheral neuropathy: a randomised, 52-week, open-label, safety study.

BACKGROUND: This 52-week study evaluated the long-term safety and tolerability of capsaicin 8% w/w (179 mg) patch repeat treatment plus standard of care (SOC) versus SOC alone in painful diabetic peripheral neuropathy (PDPN). METHODS: Phase 3, multinational, open-label, randomised, controlled, 52-week safety study, conducted in Europe. Patients were randomised to capsaicin 8% patch repeat treatment (30 or 60 min; 1-7 treatments with ≥ 8-week intervals) to painful areas of the feet plus SOC, or SOC alone. The primary objective was the safety of capsaicin 8% patch repeat treatment (30 min and 60 min applications) plus SOC versus SOC alone over 52 weeks, assessed by changes in Norfolk Quality of Life-Diabetic Neuropathy (QOL-DN) total score from baseline to end of study (EOS). Secondary safety endpoints included Utah Early Neuropathy Scale (UENS) assessments and standardised testing of sensory perception and reflex function. RESULTS: Overall, 468 patients were randomised (30 min plus SOC, n = 156; 60 min plus SOC, n = 157; SOC alone, n = 155). By EoS, mean changes in Norfolk QOL-DN total score from baseline [estimated mean difference versus SOC alone; 90% CI for difference] were: 30 min plus SOC, -27.6% [-20.9; -31.7, -10.1]; 60 min plus SOC, -32.8% [-26.1; -36.8, -15.4]; SOC alone, -6.7%. Mean changes [difference versus SOC alone] in UENS total score by EoS versus baseline were: 30 min plus SOC, -2.1 [-0.9; -1.8, 0.1]; 60 min plus SOC, -3.0 [-1.7; -2.7, -0.8]; SOC alone, -1.2. No detrimental deterioration was observed in any of the Norfolk or UENS subscales by EoS with capsaicin. Also, no worsening in sensory perception testing of sharp, warm, cold and vibration stimuli was found with capsaicin by EoS. Capsaicin treatment was well tolerated and the most frequent treatment-emergent adverse events were application site pain (30 min, 28.2%; 60 min, 29.3%), burning sensation (30 min, 9.0%; 60 min, 9.6%) and application site erythema (30 min, 7.7%; 60 min, 8.9%). CONCLUSION: In patients with PDPN, capsaicin 8% patch repeat treatment plus SOC over 52 weeks was well tolerated with no negative functional or neurological effects compared with SOC alone. TRIAL REGISTRATION: ClinicalTrials.gov registration: NCT01478607 . Date of registration November 21, 2011; retrospectively registered.

Capsaicin 8 % Patch: A Review in Peripheral Neuropathic Pain.

The capsaicin 8 % patch (QUTENZA®) is an adhesive patch containing a high concentration (8 % w/w) of synthetic capsaicin, a selective agonist of transient receptor potential vanilloid 1 channel. It is approved for treatment of peripheral neuropathic pain in adults either alone or in combination with other medicinal products for pain in the EU; it is only approved to treat postherpetic neuralgia (PHN) in the USA. In patients with painful diabetic peripheral neuropathy (PDPN), a single 30-min application of the capsaicin 8 % patch significantly improved pain relief and sleep quality compared with placebo in a 12-week double-blind trial. In a 52-week, randomized trial, up to seven consecutive 30-min treatments with the capsaicin 8 % patch (≤7 treatments each at least 8 weeks apart) plus standard of care therapy was associated with sustained pain relief and no negative neurological safety consequences compared with standard of care. In two randomized trials, a single 60-min application of the capsaicin 8 % patch reduced pain scores significantly more than a low-concentration (0.04 %) capsaicin control patch in patients with PHN. Capsaicin 8 % patch treatment was noninferior to pregabalin (optimized dosage) in a randomized trial in patients with nondiabetic peripheral neuropathic pain. Results in two trials in patients with HIV-AN were equivocal, with a significant improvement in pain intensity observed in one trial, but not in the other. The capsaicin 8 % patch was associated with expected, transient, capsaicin-related application-site adverse events such as erythema and pain.

Pregabalin reduces acute inflammatory and persistent pain associated with nerve injury and cancer in rat models of orofacial pain.

AIMS: To assess the analgesic effect of pregabalin in orofacial models of acute inflammatory pain and of persistent pain associated with nerve injury and cancer, and so determine its effectiveness in controlling orofacial pains having different underlying mechanisms. METHODS: Orofacial capsaicin and formalin tests were employed in male Wistar rats to assess the influence of pregabalin (or vehicle) pretreatment in acute pain models, and the results from these experiments were analyzed by one-way analysis of variance (ANOVA) followed by Newman Keuls post-hoc test. Pregabalin (or vehicle) treatment was also tested on the facial heat hyperalgesia that was evaluated in rats receiving injection of the inflammatory irritant carrageenan into the upper lip, as well as after constriction of the infraorbital nerve (a model of trigeminal neuropathic pain), or after inoculation of tumor cells into the facial vibrissal pad; two-way repeated measures ANOVA followed by Newman-Keuls post-hoc test was used to analyze data from these experiments. RESULTS: Facial grooming induced by capsaicin was abolished by pretreatment with pregabalin at 10 and 30 mg/kg. However, pregabalin failed to modify the first phase of the formalin response, but reduced the second phase at both doses (10 and 30 mg/kg). In addition, treatment of rats with pregabalin reduced the heat hyperalgesia induced by carrageenan, as well as by nerve injury and facial cancer. CONCLUSION: Pregabalin produced a marked antinociceptive effect in rat models of facial inflammatory pain as well as in facial neuropathic and cancer pain models, suggesting that it may represent an important agent for the clinical control of orofacial pain.

Capsaicin treatment reduces nasal hyperreactivity and transient receptor potential cation channel subfamily V, receptor 1 (TRPV1) overexpression in patients with idiopathic rhinitis.

BACKGROUND: Idiopathic rhinitis (IR) is a prevalent condition for which capsaicin nasal spray is the most effective treatment. However, the mechanisms underlying IR and the therapeutic action of capsaicin remain unknown. OBJECTIVE: We sought to investigate the molecular and cellular bases of IR and the therapeutic action of capsaicin. METHODS: Fourteen patients with IR and 12 healthy control subjects (HCs) were treated with intranasal capsaicin. The therapeutic effect was assessed in patients with IR by using visual analog scale and therapeutic response evaluation scores, and nasal hyperreactivity was evaluated by means of cold dry air provocation. Nasal samples served to measure the levels of neuromediators and expression of chemosensory cation channels, protein gene product 9.5 (PGP 9.5), and the mast cell marker c-kit. The effects of capsaicin were also tested in vitro on human nasal epithelial cells and mast cells. RESULTS: Patients with IR had higher baseline transient receptor potential cation channel subfamily V, receptor 1 (TRPV1) expression in the nasal mucosa and higher concentrations of substance P (SP) in nasal secretions than HCs. Symptomatic relief was observed in 11 of 14 patients with IR after capsaicin treatment. Expression of TRPV1; transient receptor potential cation channel subfamily M, receptor 8 (TRPM8); and PGP 9.5 was only reduced in patients with IR after capsaicin treatment. Capsaicin did not alter c-KIT expression or nasal epithelial morphology in patients with IR and HCs nor did it induce apoptosis or necrosis in cultured human nasal epithelial cells and mast cells. CONCLUSION: IR features an overexpression of TRPV1 in the nasal mucosa and increased SP levels in nasal secretions. Capsaicin exerts its therapeutic action by ablating the TRPV1-SP nociceptive signaling pathway in the nasal mucosa.

The anti-inflammatory effect of diclofenac is considerably augmented by topical capsaicinoids-containing patch in carrageenan-induced paw oedema of rat.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most used drugs in musculoskeletal disorders, but their systemic adverse effects limit their therapeutic benefit in local inflammation. On the other hand, topical preparations of capsaicinoids are widely used for musculoskeletal disorders as a complementary therapy. In this study, the effects of both topical capsaicinoids-containing patch and local subcutaneous capsaicin application on the anti-inflammatory action of NSAID were examined. Carrageenan-induced paw oedema of rats was used as the inflammation model. The volume and weight of the paw oedema and plasma extravasation in the paw were determined after carrageenan injection. The systemic application of diclofenac (3 mg/kg), which is an NSAID, significantly decreased the volume and weight of the paw oedema. Topical capsaicinoids-containing patch application or local capsaicin injection (2, 10, 20 µg/paw) alone did not cause any effect on oedema volume and weight. However, the combination of diclofenac with topical capsaicinoids-containing patch significantly increased the effectiveness of diclofenac on inflammation. Evans blue content of the paws that represents plasma extravasation was decreased by capsaicinoids-containing patch with and without diclofenac and diclofenac combination with the lowest dose of capsaicin injection. The results of this study indicate that topical application of capsaicinoids-containing patch enhances the anti-inflammatory effect of diclofenac and its beneficial effect may not purely relate to its capsaicin content. In the treatment of local inflammatory disorders, the combination of NSAID with topical capsaicinoids-containing patch could increase the anti-inflammatory efficiency of drug without systemic side effects.

The capsaicin 8% patch for neuropathic pain in clinical practice: a retrospective analysis.

OBJECTIVE: To investigate the response of patients with peripheral neuropathic pain (PNP) to capsaicin 8% patch treatment in a clinical setting. DESIGN: Retrospective analysis. SETTING: The Clinic for Pain Therapy and Palliative Medicine at the Medical Centre for the region of Aachen, Germany. SUBJECTS: Patients diagnosed with PNP who attended the clinic for capsaicin 8% patch treatment between January 13, 2010 and February 7, 2011. OUTCOME MEASURES: Pain intensity was assessed using the Numeric Pain Rating Scale (NPRS) at baseline and following each capsaicin 8% patch treatment. Changes in prescribed concomitant neuropathic pain (NP) medications and response duration were recorded. RESULTS: Overall, 68 patients with PNP conditions, including facial neuropathy (severe trigeminal neuralgia in V2), polyneuropathy, post-herpetic neuralgia, and mononeuropathies, received 96 treatments with the capsaicin 8% patch. The 53 patients with a follow-up of ≥8 weeks demonstrated a 48.4% mean reduction in NPRS score from baseline to Weeks 1-8. Among the 37 responders (those exhibiting ≥30% reduction in NPRS score from baseline to Weeks 1-8), the median time to re-treatment was 125 days. Following treatment, there was a significant (P < 0.001) 54% reduction in the mean number of prescribed concomitant NP medications taken by patients. CONCLUSIONS: This analysis demonstrates that in clinical practice, the capsaicin 8% patch provides rapid and sustained pain reductions in patients with a variety of PNP conditions and a significant reduction in prescribed concomitant NP medications. The capsaicin 8% patch can be a valuable addition to the NP treatment armory for certain patients.

Amygdala activity contributes to the dissociative effect of cannabis on pain perception.

Cannabis is reported to be remarkably effective for the relief of otherwise intractable pain. However, the bases for pain relief afforded by this psychotropic agent are debatable. Nonetheless, the frontal-limbic distribution of cannabinoid receptors in the brain suggests that cannabis may target preferentially the affective qualities of pain. This central mechanism of action may be relevant to cannabinoid analgesia in humans, but has yet to be demonstrated. Here, we employed functional magnetic resonance imaging to investigate the effects of delta-9-tetrahydrocannabinol (THC), a naturally occurring cannabinoid, on brain activity related to cutaneous ongoing pain and hyperalgesia that were temporarily induced by capsaicin in healthy volunteers. On average, THC reduced the reported unpleasantness, but not the intensity of ongoing pain and hyperalgesia: the specific analgesic effect on hyperalgesia was substantiated by diminished activity in the anterior mid cingulate cortex. In individuals, the drug-induced reduction in the unpleasantness of hyperalgesia was positively correlated with right amygdala activity. THC also reduced functional connectivity between the amygdala and primary sensorimotor areas during the ongoing-pain state. Critically, the reduction in sensory-limbic functional connectivity was positively correlated with the difference in drug effects on the unpleasantness and the intensity of ongoing pain. Peripheral mechanisms alone cannot account for the dissociative effects of THC on the pain that was observed. Instead, the data reveal that amygdala activity contributes to interindividual response to cannabinoid analgesia, and suggest that dissociative effects of THC in the brain are relevant to pain relief in humans.

Capsaicin.

Questions from patients about analgesic pharmacotherapy and responses from the authors are presented to help educate patients and make them more effective self-advocates. The topics addressed in this issue are postherpetic neuralgia and capsaicin and a discussion about symptoms, causes, and treatments is presented.

Disparate changes in the expression of transient receptor potential vanilloid type 1 receptor mRNA and protein in dorsal root ganglion neurons following local capsaicin treatment of the sciatic nerve in the rat.

In situ hybridization, quantitative reverse transcription polymerase chain reaction (RT-PCR), immunohistochemistry, and Western blot analysis were applied to study the changes in expression of the major nociceptive ion channel transient receptor potential vanilloid type 1 receptor (TRPV1) after the perineural application of capsaicin or nerve transection. In control rats, quantitative morphometric and statistical analyses of TRPV1 protein and mRNA expression in L5 dorsal root ganglion cells revealed distinct populations of small (type C) and small-to-medium (type B) neurons, which showed very high and moderate levels of TRPV1, whereas larger (type A) neurons mostly did not express this receptor. After either transection or capsaicin treatment of the sciatic nerve, immunohistochemistry and Western blotting demonstrated a massive (up to 80%) decrease in the proportion of TRPV1-immunoreactive neurons and TRPV1 protein at all postoperative survival times. In situ hybridization indicated marked decreases (up to 85%) in the proportion of neurons that expressed TRPV1 mRNA after sciatic nerve transection. In contrast, although perineural treatment with capsaicin resulted in similar substantial decreases in the proportions of type B and C neurons of the L5 dorsal root ganglia 3 days postoperatively, a clear-cut tendency to recovery was observed thereafter. Hence, the proportions of both type B and C neurons expressing TRPV1 mRNA reached up to 70% of the control levels at 30 days postoperatively. In accord with these findings, quantitative RT-PCR revealed a marked and significant recovery in TRPV1 mRNA after perineural capsaicin but not after nerve transection. These observations suggest the involvement of distinct cellular mechanisms in the regulation of the TRPV1 mRNA expression of damaged neurons, specifically triggered by the nature of the injury. The present findings imply that the antinociceptive and anti-inflammatory effects of perineurally applied capsaicin involve distinct changes in neuronal TRPV1 mRNA expression and long-lasting alterations in (post)translational regulation.

TRPV1 and TRPA1 stimulation induces MUC5B secretion in the human nasal airway in vivo.

AIM: Nasal transient receptor potential vanilloid 1 (TRPV1) stimulation with capsaicin produces serous and mucinous secretion in the human nasal airway. The primary aim of this study was to examine topical effects of various TRP ion channel agonists on symptoms and secretion of specific mucins: mucin 5 subtype AC (MUC5AC) and B (MUC5B). METHODS: Healthy individuals were subjected to nasal challenges with TRPV1 agonists (capsaicin, olvanil and anandamide), TRP ankyrin 1 (TRPA1) agonists (cinnamaldehyde and mustard oil) and a TRP melastatin 8 (TRPM8) agonist (menthol). Symptoms were monitored, and nasal lavages were analysed for MUC5AC and MUC5B, i.e. specific mucins associated with airway diseases. In separate groups of healthy subjects, nasal biopsies and brush samples were analysed for TRPV1 and MUC5B, using immunohistochemistry and RT-qPCR. Finally, calcium responses and ciliary beat frequency were measured on isolated ciliated epithelial cells. RESULTS: All TRP agonists induced nasal pain or smart. Capsaicin, olvanil and mustard oil also produced rhinorrhea. Lavage fluids obtained after challenge with capsaicin and mustard oil indicated increased levels of MUC5B, whereas MUC5AC was unaffected. MUC5B and TRPV1 immunoreactivities were primarily localized to submucosal glands and peptidergic nerve fibres, respectively. Although trpv1 transcripts were detected in nasal brush samples, functional responses to capsaicin could not be induced in isolated ciliated epithelial cells. CONCLUSION: Agonists of TRPV1 and TRPA1 induced MUC5B release in the human nasal airways in vivo. These findings may be of relevance with regard to the regulation of mucin production under physiological and pathophysiological conditions.

Topical therapies for osteoarthritis.

This review discusses the pharmacology, analgesic efficacy, safety and tolerability of topical NSAIDs, salicylates and capsaicin for the management of osteoarthritis (OA) pain. Topical therapies present a valuable therapeutic option for OA pain management, with substantial evidence supporting the efficacy and safety of topical NSAIDs, but less robust support for capsaicin and salicylates. We define topical therapies as those intended to act locally, in contrast to transdermal therapies intended to act systemically. Oral therapies for patients with mild to moderate OA pain include paracetamol (acetaminophen) and NSAIDs. Paracetamol has only weak efficacy at therapeutic doses and is hepatotoxic at doses >3.25 g/day. NSAIDs have demonstrated efficacy in patients with OA, but are associated with dose-, duration- and age-dependent risks of gastrointestinal, cardiovascular, renal, haematological and hepatic adverse events (AEs), as well as clinically meaningful drug interactions. To minimize AE risks, treatment guidelines for OA suggest minimizing NSAID exposure by prescribing the lowest effective dose for the shortest duration of time. Systemic NSAID exposure may also be limited by prescribing topical NSAIDs, particularly in patients with OA pain limited to a few superficial joints. Topical NSAIDs have been available in Europe for decades and were introduced to provide localized analgesia with minimal systemic NSAID exposure. Guidelines of the American Academy of Orthopaedic Surgeons, European League Against Rheumatism (EULAR), Osteoarthritis Research Society International, and National Institute for Health and Clinical Excellence (NICE) state that topical NSAIDs may be considered for patients with mild to moderate OA of the knee or hand, particularly in patients with few affected joints and/or a history of sensitivity to oral NSAIDs. In fact, the EULAR and NICE guidelines state that topical NSAIDs should be considered before oral therapies. Clinical trials of topical NSAIDs, most notably formulations of diclofenac and ketoprofen, have shown efficacy significantly superior to placebo and similar to oral NSAIDs. Most topical NSAIDs (piroxicam being the exception) have shown improved safety and tolerability compared with oral NSAIDs. Topical salicylates and capsaicin are available in the US without a prescription, but neither has shown substantial efficacy in clinical trials, and both have potential to cause serious AEs. Accidental poisonings have been reported with salicylates, and concerns exist that capsaicin-induced nerve desensitization is not fully reversible and that its autonomic nerve effects may increase the risk of skin ulcers in diabetic patients.

Antihyperalgesic effects of clomipramine and tramadol in a model of posttraumatic trigeminal neuropathic pain in mice.

AIMS: To develop a behavioral model in mice that is capable of mimicking some distinctive symptoms of human posttraumatic trigeminal neuropathic pain such as spontaneous pain, cold allodynia, and chemical÷inflammatory hyperalgesia, and to use this model to investigate the antinociceptive effects of clomipramine and tramadol, two drugs used for the treatment of neuropathic pain. METHODS: A partial tight ligature of the right infraorbital nerve by an intraoral access or a sham procedure was performed. Fourteen days later, mice were subcutaneously injected with saline or drugs and the spontaneous nociceptive behavior, as well as the responses to topical acetone and to formalin or capsaicin injected into the ipsilateral vibrissal pad, were assessed. Data were analyzed by ANOVA. RESULTS: Neuropathic mice exhibited an increased spontaneous rubbing÷scratching of the ipsilateral vibrissal pad, together with enhanced responses to cooling (acetone) and the chemical irritants (formalin, capsaicin). Clomipramine and tramadol produced an antihyperalgesic effect on most of these nociceptive responses, but tramadol was ineffective on capsaicin-induced hyperalgesia. CONCLUSION: Nociceptive responses in this neuropathic pain model in mice exhibited a pattern consistent with the pain described by posttraumatic trigeminal neuropathic patients. The selective antihyperalgesic effect obtained with two commonly used drugs for treating neuropathic pain confirms the validity of this preclinical model.

Effect of duration of postherpetic neuralgia on efficacy analyses in a multicenter, randomized, controlled study of NGX-4010, an 8% capsaicin patch evaluated for the treatment of postherpetic neuralgia.

BACKGROUND: Postherpetic neuralgia (PHN) is a painful and difficult to treat complication of acute herpes zoster. Current treatment options provide only partial relief and are often limited by poor tolerability. We evaluated the safety and efficacy of a single 60-minute application of NGX-4010, an 8% capsaicin patch, in patients with PHN. METHODS: This multicenter, double-blind, controlled study randomized 155 patients 2:1 to receive either NGX-4010 or a 0.04% capsaicin control patch. Patients were at least 18 years old with PHN for at least 3 months, and an average Numeric Pain Rating Scale (NPRS) score of 3 to 9. The primary efficacy endpoint was the percentage change in NPRS score from baseline to weeks 2-8. RESULTS: The mean percent reduction in "average pain for the past 24 hours" NPRS scores from baseline to weeks 2-8 was greater in the NGX-4010 group (36.5%) compared with control (29.9%) although the difference was not significant (p = 0.296). PGIC analysis demonstrated that more NGX-4010 recipients considered themselves improved (much, or very much) compared with control at weeks 8 and 12, but the differences did not reach statistical significance. Post hoc analyses of patients with PHN for at least 6 months showed significantly greater reductions in "average pain for the past 24 hours" NPRS scores from baseline to weeks 2-8 in NGX-4010 patients compared to controls (37.6% versus 23.4%; p = 0.0291). PGIC analysis in this subgroup demonstrated that significantly more NGX-4010 recipients considered themselves much or very much improved compared with control at week 12 (40% versus 20%; p = 0.0403;). CONCLUSIONS: Although treatment appeared to be safe and well tolerated, a single 60-minute application of NGX-4010 failed to show efficacy in this study which included patients with PHN for less than 6 months. Large reductions in pain observed among control patients with pain for less than 6 months may have been due to spontaneous resolution of PHN, may have confounded the results of the prespecified analyses, and should be taken into account when designing PHN studies. TRIAL REGISTRATION: NCT00068081.

Capsaicin. Neuropathic pain: playing with fire....

5% lidocaine medicated plasters are available for local treatment of neuropathic pain. Treatment is generally poorly effective but has few adverse effects, other than local erythema. Capsaicin is a natural chilli pepper extract that depletes sensory nerve endings of substance P, a pain neurotransmitter. It is authorised in the European Union for the treatment of nondiabetic neuropathic pain, in the form of cutaneous patches containing 8% capsaicin. Clinical evaluation of capsaicin patches does not include any trials versus lidocaine plasters. Eight double-blind trials have compared 8% capsaicin patches versus 0.04% capsaicin patches, 5 in postherpetic neuralgia, and 3 in HIV-related neuropathic pain. These trials are only vaguely described in the European Medicines Agency report. Taken separately, they yielded divergent results. It was only when some of the trials were pooled for analysis that any differences emerged between the two doses of capsaicin. The clinical implications are unclear, but efficacy is at best modest. Capsaicin is an irritant that frequently provokes pain and erythema at the site of patch application, and 3% of patients using the patches experienced transient arterial hypertension that the investigators attributed to this pain. Some pharmacological data suggest that repeated application of 8% capsaicin patches might provoke painful nerve damage in the long-term. Patch application and removal by a third party is delicate, due to the strong irritant potential of capsaicin. In practice, when a patient with neuropathic pain requires local treatment, in the absence of a better alternative, it is better to use lidocaine plasters, which are better tolerated and with which we have more experience.

Antinociceptive effects of citronellal in formalin-, capsaicin-, and glutamate-induced orofacial nociception in rodents and its action on nerve excitability.

AIMS: To evaluate the antinociceptive effects of citronellal (CTL) on formalin-, capsaicin-, and glutamate-induced orofacial nociception in mice and to investigate whether such effects might involve a change in neural excitability. METHODS: Male mice were pretreated with CTL (50, 100, and 200 mg/kg, ip), morphine (5 mg/kg, ip), or vehicle (distilled water plus one drop of Tween 80 0.2%) before formalin (20 microL, 2%), capsaicin (20 microL, 2.5 microg) or glutamate (40 microL, 25 microM) injection into the right vibrissa. Sciatic nerve recordings were made using the single sucrose gap technique in rats. The data obtained were analyzed by ANOVA followed by Dunnett's test for the behavioral analyses and by the Student t test for CAP evaluation. RESULTS: Pretreatment with CTL was effective in reducing nociceptive face-rubbing behavior in both phases of the formalin test, which was also naloxone-sensitive. CTL produced significantly antinociceptive effect at all doses in the capsaicin- and glutamate- tests. Rota-rod testing indicated that such results were unlikely to be provoked by motor abnormality. Recordings using the single sucrose gap technique revealed that CTL (10 mM) could reduce the excitability of the isolated sciatic nerve through a diminution of the compound action potential amplitude by about 42.4% from control recordings. CONCLUSION: These results suggest that CTL might represent an important tool for management and/or treatment of orofacial pain.

Topical therapy for osteoarthritis: clinical and pharmacologic perspectives.

Nonsteroidal anti-inflammatory drugs (NSAIDs) have shown efficacy in patients with osteoarthritis (OA) pain but are also associated with a dose-dependent risk of gastrointestinal, cardiovascular, hematologic, hepatic, and renal adverse events (AEs). Topical NSAIDs were developed to provide analgesia similar to their oral counterparts with less systemic exposure and fewer serious AEs. Topical NSAIDs have long been available in Europe for the management of OA, and guidelines of the European League Against Rheumatism and the Osteoarthritis Research Society International specify that topical NSAIDs are preferred over oral NSAIDs for patients with knee or hand OA of mild-to-moderate severity, few affected joints, and/or a history of sensitivity to oral NSAIDs. In contrast, the guidelines of the American Pain Society and American College of Rheumatology have in the past recommended topical methyl salicylate and topical capsaicin, but not topical NSAIDs. This reflects the fact that the American guidelines were written several years before the first topical NSAID was approved for use in the United States. Neither salicylates nor capsaicin have shown significant efficacy in the treatment of OA. In October 2007, diclofenac sodium 1% gel (Voltaren Gel) became the first topical NSAID for OA therapy approved in the United States following a long history of use internationally. Topical diclofenac sodium 1% gel delivers effective diclofenac concentrations in the affected joint with limited systemic exposure. Clinical trial data suggest that diclofenac sodium 1% gel provides clinically meaningful analgesia in OA patients with a low incidence of systemic AEs. This review discusses the pharmacology, clinical efficacy, and safety profiles of diclofenac sodium 1% gel, salicylates, and capsaicin for the management of hand and knee OA.