Treatment of reflex sympathetic dystrophy with topical capsaicin. Case report

[Pronounced symptom deterioration in complex regional pain syndrome type II after isolated application of a highly concentrated capsaicin patch. A case report]

Topical 8 % capsaicin is an established therapeutic option for the treatment of peripheral neuropathic pain. In accordance with the internationally accepted definition, complex regional pain syndrome (CRPS) type II is a form of neuropathic pain so that capsaicin plasters represent a treatment option. However, for the treatment of CRPS it is recommended that painful stimuli should be avoided but capsaicin induces a strong nociceptive stimulation and so its use is at present controversial. We report on the course of such an application in a patient who developed CRPS type II with intractable neuropathic pain after hallux surgery. As a result of a single treatment with capsaicin a pronounced recurrence developed with central nervous symptoms.

Final report on the safety assessment of capsicum annuum extract, capsicum annuum fruit extract, capsicum annuum resin, capsicum annuum fruit powder, capsicum frutescens fruit, capsicum frutescens fruit extract, capsicum frutescens resin, and capsaicin

Capsicum-derived ingredients function as skin-conditioning agents--miscellaneous, external analgesics, flavoring agents, or fragrance components in cosmetics. These ingredients are used in 19 cosmetic products at concentrations as high as 5%. Cosmetic-grade material may be extracted using hexane, ethanol, or vegetable oil and contain the full range of phytocompounds that are found in the Capsicum annuum or Capsicum frutescens plant (aka red chiles), including Capsaicin. Aflatoxin and N-nitroso compounds (N-nitrosodimethylamine and N-nitrosopyrrolidine) have been detected as contaminants. The ultraviolet (UV) absorption spectrum for Capsicum Annuum Fruit Extract indicates a small peak at approximately 275 nm, and a gradual increase in absorbance, beginning at approximately 400 nm. Capsicum and paprika are generally recognized as safe by the U.S. Food and Drug Administration for use in food. Hexane, chloroform, and ethyl acetate extracts of Capsicum Frutescens Fruit at 200 mg/kg resulted in death of all mice. In a short-term inhalation toxicity study using rats, no difference was found between vehicle control and a 7% Capsicum Oleoresin solution. In a 4-week feeding study, red chilli (Capsicum annuum) in the diet at concentrations up to 10% was relatively nontoxic in groups of male mice. In an 8-week feeding study using rats, intestinal exfoliation, cytoplasmic fatty vacuolation and centrilobular necrosis of hepatocytes, and aggregation of lymphocytes in the portal areas were seen at 10% Capsicum Frutescens Fruit, but not 2%. Rats fed 0.5 g/kg day-1 crude Capsicum Fruit Extract for 60 days exhibited no significant gross pathology at necropsy, but slight hyperemia of the liver and reddening of the gastric mucosa were observed. Weanling rats fed basal diets supplemented with whole red pepper at concentrations up to 5.0% for up to 8 weeks had no pathology of the large intestines, livers, and kidneys, but destruction of the taste buds and keratinization and erosion of the gastrointestinal (GI) tract were noted in groups fed 0.5% to 5.0% red pepper. The results of 9-and 12-month extension of this study showed normal large intestines and kidneys. In rabbits fed Capsicum Annuum Powder at 5 mg/kg day-1 in the diet daily for 12 months damage to the liver and spleen was noted. A rabbit skin irritation test of Capsicum Annuum Fruit Extract at concentrations ranging from 0.1% to 1.0% produced no irritation, but Capsicum Frutescens Fruit Extract induced concentration-dependent (at 25 to 500 microg/ml) cytotoxicity in a human buccal mucosa fibroblast cell line. An ethanol extract of red chili was mutagenic in Salmonella typhimurium TA98, but not in TA100, or in Escherichia coli. Other genotoxicity assays gave a similar pattern of mixed results. Adenocarcinoma of the abdomen was observed in 7/20 mice fed 100 mg red chilies per day for 12 months; no tumors were seen in control animals. Neoplastic changes in the liver and intestinal tumors were observed in rats fed red chili powder at 80 mg/kg day-1 for 30 days, intestinal and colon tumors were seen in rats fed red chili powder and 1,2-dimethyl hydrazine, but no tumors were observed in controls. In another study in rats, however, red chile pepper in the diet at the same dose decreased the number of tumors seen with 1,2-dimethylhydrazine. Other feeding studies evaluated the effect of red chili peppers on the incidence of stomach tumors produced by N-methyl-N'-nitro-N-nitrosoguanidine, finding that red pepper had a promoting effect. Capsicum Frutescens Fruit Extract promoted the carcinogenic effect of methyl(acetoxymethyl)nitrosamine (carcinogen) or benzene hexachloride (hepatocarcinogen) in inbred male and female Balb/c mice dosed orally (tongue application). Clinical findings include symptoms of cough, sneezing, and runny nose in chili factory workers. Human respiratory responses to Capsicum Oleoresin spray include burning of the throat, wheezing, dry cough, shortness of breath, gagging, gasping, inability to breathe or speak, and, rarely, cyanosis, apnea, and respiratory arrest. A trade name mixture containing 1% to 5% Capsicum Frutescens Fruit Extract induced very slight erythema in 1 of 10 volunteers patch tested for 48 h. Capsicum Frutescens Fruit Extract at 0.025% in a repeated-insult patch test using 103 subjects resulted in no clinically meaningful irritation or allergic contact dermatitis. One epidemiological study indicated that chili pepper consumption may be a strong risk factor for gastric cancer in populations with high intakes of chili pepper; however, other studies did not find this association. Capsaicin functions as an external analgesic, a fragrance ingredient, and as a skin-conditioning agent--miscellaneous in cosmetic products, but is not in current use. Capsaicin is not generally recognized as safe and effective by the U.S. Food and Drug Administration for fever blister and cold sore treatment, but is considered to be safe and effective as an external analgesic counterirritant. Ingested Capsaicin is rapidly absorbed from the stomach and small intestine in animal studies. Subcutaneous injection of Capsaicin in rats resulted in a rise in the blood concentration, reaching a maximum at 5 h; the highest tissue concentrations were in the kidney and lowest in the liver. In vitro percutaneous absorption of Capsaicin has been demonstrated in human, rat, mouse, rabbit, and pig skin. Enhancement of the skin permeation of naproxen (nonsteroidal anti-inflammatory agent) in the presence of Capsaicin has also been demonstrated. Pharmacological and physiological studies demonstrated that Capsaicin, which contains a vanillyl moiety, produces its sensory effects by activating a Ca2 +-permeable ion channel on sensory neurons. Capsaicin is a known activator of vanilloid receptor 1. Capsaicin-induced stimulation of prostaglandin biosynthesis has been shown using bull seminal vesicles and rheumatoid arthritis synoviocytes. Capsaicin inhibits protein synthesis in Vero kidney cells and human neuroblastoma SHSY-5Y cells in vitro, and inhibits growth of E. coli, Pseudomonas solanacearum, and Bacillus subtilis bacterial cultures, but not Saccharomyces cerevisiae. Oral LD50 values as low as 161.2 mg/kg (rats) and 118.8 mg/kg (mice) have been reported for Capsaicin in acute oral toxicity studies, with hemorrhage of the gastric fundus observed in some of the animals that died. Intravenous, intraperitoneal, and subcutaneous LD50 values were lower. In subchronic oral toxicity studies using mice, Capsaicin produced statistically significant differences in the growth rate and liver/body weight increases. Capsaicin is an ocular irritant in mice, rats, and rabbits. Dose-related edema was observed in animals receiving Capsaicin injections into the hindpaw (rats) or application to the ear (mice). In guinea pigs, dinitrochlorobenzene contact dermatitis was enhanced in the presence of Capsaicin, injected subcutaneously, whereas dermal application inhibited sensitization in mice. Immune system effects have been observed in neonatal rats injected subcutaneously with Capsaicin. Capsaicin produced mixed results in S. typhimurium micronucleus and sister-chromatid exchange genotoxicity assays. Positive results for Capsaicin were reported in DNA damage assays. Carcinogenic, cocarcinogenic, anticarcinogenic, antitumorigenic, tumor promotion, and anti-tumor promotion effects of Capsaicin have been reported in animal studies. Except for a significant reduction in crown-rump length in day 18 rats injected subcutaneously with Capsaicin (50 mg/kg) on gestation days 14, 16, 18, or 20, no reproductive or developmental toxicity was noted. In pregnant mice dosed subcutaneously with Capsaicin, depletion of substance P in the spinal cord and peripheral nerves of pregnant females and fetuses was noted. In clinical tests, nerve degeneration of intracutaneous nerve fibers and a decrease in pain sensation induced by heat and mechanical stimuli were evident in subjects injected intradermally with Capsaicin. An increase in mean inspiratory flow was reported for eight normal subjects who inhaled nebulized 10(-7) M Capsaicin. The results of provocative and predictive tests involving human subjects indicated that Capsaicin is a skin irritant. Overall, studies suggested that these ingredients can be irritating at low concentrations. Although the genotoxicity, carcinogenicity, and tumor promotion potential of Capsaicin have been demonstrated, so have opposite effects. Skin irritation and other tumor-promoting effects of Capsaicin appear to be mediated through interaction with the same vanilloid receptor. Given this mechanism of action and the observation that many tumor promoters are irritating to the skin, the Panel considered it likely that a potent tumor promoter may also be a moderate to severe skin irritant. Thus, a limitation on Capsaicin content that would significantly reduce its skin irritation potential is expected to, in effect, lessen any concerns relating to tumor promotion potential. Because Capsaicin enhanced the penetration of an anti-inflammatory agent through human skin, the Panel recommends that care should be exercised in using ingredients that contain Capsaicin in cosmetic products. The Panel advised industry that the total polychlorinated biphenyl (PCB)/pesticide contamination should be limited to not more than 40 ppm, with not more than 10 ppm for any specific residue, and agreed on the following limitations for other impurities: arsenic (3 mg/kg max), heavy metals (0.002% max), and lead (5 mg/kg max). Industry was also advised that aflatoxin should not be present in these ingredients (the Panel adopted < or =15 ppb as corresponding to "negative" aflatoxin content), and that ingredients derived from Capsicum annuum and Capsicum Frutescens Plant species should not be used in products where N-nitroso compounds may be formed. (ABSTRACT TRUNCATED)

Physical agents used in the management of chronic pain by physical therapists

Evidence supporting the use of specific physical agents in the management of chronic pain conditions is not definitive; it is largely incomplete and sometimes contradictory. However, the use of agents in chronic pain management programs is common. Within the broad use of physical agents, they are rarely the sole modality of treatment. A 1995 American Physical Therapy Association position statement asserts that "Without documentation which justifies the necessity of the exclusive use of physical agents/modalities, the use of physical agents/modalities, in the absence of other skilled therapeutic or educational intervention, should not be considered physical therapy". Physical agents may serve as useful adjunctive modalities of pain relief or to enhance the effectiveness of other elements in therapy geared toward resolution of movement impairments and restoration of physical function. Given that a conclusive aggregate of findings is unlikely to exist for all permutations of patient conditions, combined with interacting therapeutic modalities, an evidence-based approach to pain management is not always possible or beneficial to the patient. In the face of inconclusive evidence, a theory-based approach may help determine if the therapeutic effect ofa given physical agent has the possibility of being a useful clinical tool in the context of treating a particular patient's mechanism of pain generation. Until controlled efficacy findings are definitive, careful individual patient response monitoring of thoughtful theoretical application of adjunctive physical agents may be a prudent approach to the management of chronic pain.

Treatment of complex regional pain syndrome type I of the hand with a series of intravenous regional sympathetic blocks with guanethidine and lidocaine

The aim of this study was to evaluate the efficacy of guanethidine and lidocaine in the treatment of complex regional pain syndrome (CRPS) type I of the hand. Seventeen patients, aged between 33 and 72 years, suffering from CRPS type I of the hand received two series of intravenous regional sympathetic block (Bier's block) sessions with guanethidine and lidocaine according to the following therapeutic protocol: (1) 5 sessions (once every second day) composed of intravenous regional administration of 15 mg guanethidine and 1 mg lidocaine/kg body weight each and (2) 20 sessions (twice a week) composed of intravenous regional administration of 10 mg guanethidine and 1 mg lidocaine/kg body weight each. Complete disappearance of pain and return of the normal function and movement of the extremity were achieved. No side effects were observed. The above-described therapeutic protocol method resulted in excellent pain relief and full restoration of both function and range of movement of the affected extremity in 17 patients suffering from CRPS type I of the hand.

Vanilloid receptor ligands: hopes and realities for the future

Neurons possessing C-fibers transmit nociceptive information into the central nervous system and participate in various reflex responses. These neurons carry receptors that bind capsaicin, recently identified as the vanilloid VR1 receptor. Excitation of these cells by capsaicin is followed by a lasting refractory state, termed desensitisation, in which the neurons fail to respond to a variety of noxious stimuli. Desensitisation to capsaicin has a clear therapeutic potential in relieving neuropathic pain and ameliorating urinary bladder overactivity, just to cite 2 important examples. Vanilloids may also be beneficial in the treatment of benign prostate hyperplasia (BPH). Since the majority of elderly patients have neuropathic pain co-existent with urinary incontinence and/or BPH, a drug that ameliorates pain and improves urinary symptoms at the same time promises to be of great clinical value in geriatric medicine. In fact, capsaicin has already been shown to have a role in the treatment of conditions that can arise in the elderly, including herpes zoster-related neuropathic pain, diabetic neuropathy, postmastectomy pain, uraemic itching associated with renal failure, and urinary incontinence. The potent VR1 agonist resiniferatoxin, now in phase II clinical trials, appears to be superior to capsaicin in terms of its tolerability profile. Recent discoveries enhance the therapeutic potential of vanilloids. The recognition that VR1 also functions as a principal receptor for protons and eicosanoids implies that VR1 antagonists may be of value in the treatment of inflammatory hyperalgesia and pain. Animal experimentation has already lent support to this assumption. The discovery of VR1-expressing cells in the brain as well as in non-neural tissues such as the kidney and urothelium places VR1 in a much broader perspective than peripheral pain perception, and is hoped to identify further, yet unsuspected, indications for vanilloid therapy. The realisation that VR1 and cannabinoid CB1 receptors have overlapping ligand recognition properties may also have far-reaching implications for vanilloid therapy. In fact, arvanil, a combined agonist of VR1 and CB1 receptors, has already proved to be a powerful analgesic drug in the mouse. From academic molecular biology laboratories to industrial drug discovery centres to the clinics, there is a steady flow of new data, forcing us to constantly revise the ways we are thinking about vanilloid receptor ligands and their hopes and realities for the future. This review covers the most promising current trends in vanilloid research with special emphasis on geriatric medicine.

Evidence for local inflammation in complex regional pain syndrome type 1

BACKGROUND

The pathophysiology of complex regional pain syndrome type 1 (CRPS 1) is still a matter of debate. Peripheral afferent, efferent and central mechanisms are supposed. Based on clinical signs and symptoms (e.g. oedema, local temperature changes and chronic pain) local inflammation is suspected.

AIM

To determine the involvement of neuropetides, cytokines and eicosanoids as locally formed mediators of inflammation.

METHODS

In this study, nine patients with proven CRPS 1 were included. Disease activity and impairment was determined by means of a Visual Analogue Scale, the McGill Pain Questionnaire, the difference in volume and temperature between involved and uninvolved extremities, and the reduction in active range of motion of the involved extremity. Venous blood was sampled from and suction blisters made on the involved and uninvolved extremities for measurement of cytokines interleukin (IL)-6, II-1beta and tumour necrosis factor-alpha (TNF-alpha), the neuropetides NPY and CRGP, and prostaglandin E2

RESULTS

The patients included in this study did have a moderate to serious disease activity and impairment. In plasma, no changes of mediators of inflammation were observed. In blister fluid, however, significantly higher levels of IL-6 and TNF-alpha in the involved extremity were observed in comparison with the uninvolved extremity.

CONCLUSIONS

This is the first time that involvement of mediators of inflammation in CRPS 1 has been so clearly and directly demonstrated. This observation opens new approaches for the succesful use and development of immunosuppressives in CRPS 1.

Neuroimmune alterations in the complex regional pain syndrome

This review focuses on some clinical aspects of the complex regional pain syndrome, such as oedema, local temperature changes and chronic pain, as a result of supposed neurogenic inflammation. Involvement of the immune system could imply the subsequent release of neuropeptides, pro-inflammatory cytokines and eicosanoids, which in turn leads to a complex cross-talk of primary and secondary generated mediators of inflammation. The development and application of drugs that act through selective receptor antagonism or enzymatic synthesis inhibition to prevent further stimulation of this cascade that could inevitably lead to chronicity of this disease are extensively discussed.

Complex regional pain syndrome type I treated with topical capsaicin: a case report

This report describes the case of a multitrauma patient who underwent an amputation of the left arm and had a complicated left crural fracture with a delayed union. He was treated in an inpatient setting for preprosthetic training for a myoelectric prosthesis and to regain walking abilities. After consolidation of the crural fracture, complex regional pain syndrome type I (CRPS I) developed in the left foreleg, which hindered mobilization. Topical capsaicin .075% was prescribed and a stress-loading mobilization schema was instituted. No other treatment modalities directed at CRPS I were added. After 6 weeks, no signs or symptoms of CRPS I were present and capsaicin was discontinued. Capsaicin is a well-accepted and documented treatment modality in neuropathic pain states such as postherpetic neuralgia. However, it has rarely been described in CRPS I. Capsaicin is discussed within the framework of recent insights in the neurobiology of nociception, and it is concluded that it may provide a theory-driven treatment for CRPS I, especially in the acute stage, that facilitates physical therapy and prevents peripheral and spinal sensitization.

Complex Regional Pain Syndromes: guidelines for therapy

This report aims to present an orderly approach to the treatment of Chronic Regional Pain Syndrome (CRPS) types I and II through an algorithm. The central theme is functional restoration: a coordinated but progressive approach that introduces each of the treatment modalities needed to achieve both remission and rehabilitation. Reaching objective and measurable rehabilitation goals is an essential element. Specific exercise therapy to reestablish function after musculoskeletal injury is central to this functional restoration. Its application to CRPS is more contingent on varying rates of progress that characterize the restoration of function in patients with CRPS. Also, the various modalities that may be used, including analgesia by pharmacologic means or regional anesthesia or the use of neuromodulation, behavioral management, and the qualitatively different approaches that are unique to the management of children with CRPS, are provided only to facilitate functional improvement in a stepwise but methodical manner. Patients with CRPS need an individual approach that requires extreme flexibility. This distinguishes the management of these conditions from other well-described medical conditions having a known pathophysiology. In particular, the special biopsychosocial factors that are critical to achieving a successful outcome are emphasized. This algorithm is a departure from the contemporary heterogeneous approach to treatment of patients with CRPS. The underlying principles are motivation, mobilization, and desensitization facilitated by the relief of pain and the use of pharmacologic and interventional procedures to treat specific signs and symptoms. Self-management techniques are emphasized, and functional rehabilitation is the key to the success of this algorithm.

Review of the effectiveness of capsaicin for painful cutaneous disorders and neural dysfunction

BACKGROUND

Topical capsaicin is known to be a safe and effective pain management adjunct for rheumatoid arthritis, osteoarthritis, neuralgias, and diabetic neuropathy. However, studies and case reports in the literature have indicated that other conditions may also benefit from capsaicin: painful or itching cutaneous disorders from operations, injuries, or tumors; neural dysfunction; or inflammation of the airways and urinary tract.

METHODS

To determine the effectiveness of capsaicin for painful cutaneous disorders and neural dysfunction, the authors analyzed data from 33 reports (MEDLINE search of 1966-96) on the efficacy of capsaicin. Outcome measures consisted of the response rate and degree of pain relief. Results from placebo-controlled trials were pooled when possible; effect of treatment was estimated by the method of DerSimonian and Laird.

RESULTS

Pain relief for postmastectomy syndrome and cluster headache was greater with capsaicin than with placebo; also, psoriasis and pruritus responded better to capsaicin. Uncontrolled studies and case reports have indicated that pain or dysfunction was less at the end of capsaicin therapy for neck pain, loin pain/hematuria syndrome, oral mucositis, rhinopathy, reflex sympathetic dystrophy syndrome, detrusor hyperreflexia, and cutaneous pain due to tumor of the skin.

CONCLUSIONS

Capsaicin is effective for psoriasis, pruritus, and cluster headache; it is often helpful for the itching and pain of postmastectomy pain syndrome, oral mucositis, cutaneous allergy, loin pain/hematuria syndrome, neck pain, amputation stump pain, and skin tumor; and it may be beneficial for neural dysfunction (detrusor hyperreflexia, reflex sympathetic dystrophy, and rhinopathy). A universal problem for many of the studies analyzed was the absence of a "burning placebo" such as camphor.

Recurrent spontaneous hemarthrosis associated with reflex sympathetic dystrophy

Reflex sympathetic dystrophy is a mysterious entity with unclear pathogenesis. The diagnosis is largely clinical and based on signs and symptoms of pain and vasomotor dysfunction. Treatment is a challenge because the underlying mechanism remains unknown. Our patient is a 75-year-old woman 2 years after left total knee replacement who presented with her second spontaneous hemarthrosis in 3 months. After arthrocentesis, dusky discoloration, edema, hyperesthesia, and decreased range of motion of the left knee and entire distal extremity were noted. Despite analgesia and physical therapy her symptoms worsened. Radiographs of her left knee showed severe periprosthetic osteopenia and a triple phase bone scan was negative. Clinically, reflex sympathetic dystrophy was considered likely and a lumbar sympathetic block was performed. The patient improved and continued to do well after a series of blocks. This is the first reported case of recurrent atraumatic hemarthrosis associated with reflex sympathetic dystrophy.

Vanilloid receptors: new insights enhance potential as a therapeutic target

Compounds related to capsaicin and its ultrapotent analog, resiniferatoxin (RTX), collectively referred to as vanilloids, interact at a specific membrane recognition site (vanilloid receptor), expressed almost exclusively by primary sensory neurons involved in nociception and neurogenic inflammation. Desensitization to vanilloids is a promising therapeutic approach to mitigate neuropathic pain and pathological conditions (e.g. vasomotor rhinitis) in which neuropeptides released from primary sensory neurons play a major role. Capsaicin-containing preparations are already commercially available for these purposes. The use of capsaicin, however, is severely limited by its irritancy, and the synthesis of novel vanilloids with an improved pungency/desensitization ratio is an on-going objective. This review highlights the emerging evidence that the vanilloid receptor is not a single receptor but a family of receptors, and that these receptors recognize not simply RTX and capsaicin structural analogs but are broader in their ligand-binding selectivity. We further focus on ligand-induced messenger plasticity, a recently discovered mechanism underlying the analgesic actions of vanilloids. Lastly, we give a brief overview of the current clinical uses of vanilloids and their future therapeutic potential. The possibility is raised that vanilloid receptor subtype-specific drugs may be synthesized, devoid of the undesirable side-effects of capsaicin.

Preventative effect of repeated nasal applications of capsaicin in cluster headache

Preliminary studies have shown that repeated nasal applications of capsaicin prevented the occurrence of cluster headache attacks. The present study was designed to verify the difference in efficacy of treatment with nasal capsaicin, depending on the side of application. Fifty-two patients affected by episodic form were divided into 2 groups, one receiving the treatment on the same side where the attacks occurred (ipsilateral side), the other on the controlateral side. Eighteen patients with a chronic form alternately received both ipsilateral and controlateral treatments. Seventy percent of the episodic patients, treated on the ipsilateral side, showed a marked amelioration whereas no improvement was noted in the patients treated on the contralateral side. The efficacy of ipsilateral treatment was emphasized by the results obtained in chronic patients. However, in these patients, the maximum period of amelioration lasted no more than 40 days. The difference between the effects of the 2 treatments (contralateral and ipsilateral) was statistically significant in both episodic and chronic sufferers. The efficacy of repeated nasal applications of capsaicin in cluster headache is congruent with previous reports on the therapeutic effect of capsaicin in other pain syndromes (post-herpetic neuralgia, diabetic neuropathy, trigeminal neuralgia) and supports the use of the drug to produce a selective analgesia.

Topical capsaicin as an adjuvant analgesic

Topical capsaicin has been studied in a variety of conditions by uncontrolled and controlled trials. It is attractive because it is a simple, safe treatment. Although these studies suggest an analgesic effect, even placebo-controlled trials have been impossible to blind due to the burning sensation induced by the capsaicin. A high placebo response rate in the controlled trials is an interesting observation and may account for the apparent salutary effect reported in the studies lacking a control. A careful scrutiny of the results of these trials to date as well as clinical experience indicate at best a modest effect with the currently available preparations with many patients failing to find relief, finding the relief unsatisfactory, or being unable to tolerate the burning sensation. Occasional patients appear to have a very good result, and these unusual cases may not be reflected by clinical trials. Topical capsaicin is generally not satisfactory as a sole therapy for chronic painful conditions, although it may serve as an adjuvant to other approaches.

Possible chemical contribution from chromic gut sutures produces disorders of pain sensation like those seen in man

Recently, it has been reported that loosely constrictive chromic gut ligatures around the sciatic nerve produce behavioral evidence of neuropathic pain in rats. It has been shown that axonal swelling after ligation results in a constriction injury associated with a decrease in the number of both large-diameter myelinated and small-diameter unmyelinated axons, but the mechanism(s) producing spontaneous pain and thermal hyperalgesia remain largely unknown. The present study systematically evaluated potential mechanisms involved in development of the behavioral changes produced by chromic gut ligatures loosely tied around the sciatic nerve. Four ligatures of either silk (4-0), plain gut (4-0), or chromic gut (4-0, 3-0, or 2-0) were placed loosely around the left sciatic nerve of male Sprague-Dawley rats. An additional group of rats had 8 x 0.5 cm sections of 4-0 chromic gut laid adjacent to the left sciatic nerve. The right sciatic nerve was exposed in all rats for sham surgery. The posture and gait of all rats was qualitatively assessed before (day 0) and for 20-30 days after surgery. Rats were tested for evidence of thermal and mechanical hyperalgesia prior to surgery, and on postoperative days 3, 5, 10, 20 and, in some groups, on day 30. Chromic gut, but not plain gut or silk, ligatures placed around or laid next to the sciatic nerve produced an alteration in the posture of rats such that most of the pressure was placed on the heel and medial aspect of the left (ligated) hind paw with the toes held together and plantar-flexed while pressure appeared to be evenly distributed on the right (sham) hind paw. As a result, a pronounced limp was evident, often with the left hind paw held in the air for prolonged periods of time during the first few days after surgery. These postural changes were most pronounced in the 2-0 and 3-0 chromic gut-treated rats. Chromic gut sutures (4-0, 3-0, or 2-0) tied loosely around the left sciatic nerve also produced a 'dose-dependent' decrease in thermal withdrawal latency that was maximal on postoperative day 3 (25%, 39%, and 41%, respectively). The magnitude of the thermal hyperalgesia declined over time such that a return to baseline was observed by postoperative day 20 in 4-0 and 3-0 chromic gut-treated rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Capsaicin: identification, nomenclature, and pharmacotherapy

OBJECTIVE

To provide a brief overview of the chemical history, analysis, nomenclature, biology, pharmacology, and pharmacotherapy of capsaicin.

DATA SOURCES

Chemical Abstracts, Biological Abstracts, and a MEDLINE search were used to identify pertinent literature; selected literature was used in this review.

DATA EXTRACTION

Original articles, reviews, and abstracts of articles were used to select material pertinent to the objectives of the review. The volume of material available prohibits comprehensive data extraction.

CONCLUSIONS

A history of the use of Capsicum spp. and the predominant active ingredient, capsaicin, the parent compound of a group of vanillyl fatty acid amides, is presented. Distinct structural differences are noted between this compound and the capsaicinoids, especially the synthetic analog nonivamide, which has appeared as an adulterant in capsaicin-labeled products. Analysis shows that although some of these synthetic analogs eventually may prove to be true natural products, conclusive evidence based on isolation and structure elucidation is still absent after decades of attempted isolation from several potential natural sources. Although the crude, dark oleoresin extract of capsicum contains over 100 distinct volatile compounds and therefore may function in many ways dissimilar to capsaicin, the oleoresin continues to be marketed in products with a high degree of variability in efficacy. Capsaicin as a pure white crystalline material, however, acts specifically by depleting stores of substance P from sensory neurons, and has been successful in the treatment of several painful conditions (e.g., rheumatoid arthritis, osteoarthritis, peripheral neuropathies.