Topical capsaicin as an adjuvant analgesic

A Review on the Management of Peripheral Neuropathic Pain Following Breast Cancer

Postmastectomy pain syndrome (PMPS) is a common and debilitating form of postsurgical pain with neuropathic characteristics, presenting as burning, stabbing, or pulling sensations after mastectomy, lumpectomy, or other breast procedures. With a prevalence of 31%, the risk factors for PMPS include younger age, psychosocial factors, radiotherapy, axillary lymph node dissection, and a history of chronic pain. This review evaluates the pharmacological and surgical options for managing PMPS. Pharmacological treatment options include antidepressants, gabapentinoids, levetiracetam, capsaicin, and topical lidocaine. Procedural and surgical options include fat grafting, nerve blocks, radiofrequency ablation, peripheral nerve surgery, serratus plane block, and botulinum toxin injections. Despite the variety of therapeutic options available for patients, further randomized trials are required to conclude whether these treatments reduce the intensity of neuropathic pain in patients with PMPS. In particular, comparative studies and the inclusion of patients across a range of pain intensities will be essential to developing a treatment algorithm for PMPS. In conclusion, current management for these patients should be tailored to their individual requirements.

Capsaicin, a Phytochemical From Chili Pepper, Alleviates the Ultraviolet Irradiation-Induced Decline of Collagen in Dermal Fibroblast via Blocking the Generation of Reactive Oxygen Species

Capsaicin, a major ingredient in chili pepper, has broad pharmaceutical applications, including relieving pain, anti-inflammation, and treating psoriasis. In dermatological biology, capsaicin has been shown to prevent the ultraviolet (UV)-induced melanogenesis via TRPV1 receptor. To strengthen the roles of capsaicin in skin function, the damaged skin, triggered by exposure to UV, was reversed by capsaicin in both in vitro and in vivo models. In cultured dermal fibroblasts, the exposure to UV induced a decrease of collagen synthesis and increases expression of matrix metalloproteinases (MMPs), generation of reactive oxygen species (ROS), and phosphorylation of Erk and c-Jun, and these events subsequently led to skin damage. However, the UV-mediated damages could be reversed by pre-treatment with capsaicin in a dose-dependent manner. The effect of capsaicin in blocking the UV-mediated collagen synthesis was mediated by reducing generation of ROS in dermal fibroblasts, instead of the receptor for capsaicin. Hence, capsaicin has high potential value in applying as an agent for anti-skin aging in dermatology.

Fight fire with fire: Neurobiology of capsaicin-induced analgesia for chronic pain

Capsaicin, the pungent ingredient in chili peppers, produces intense burning pain in humans. Capsaicin selectively activates the transient receptor potential vanilloid 1 (TRPV1), which is enriched in nociceptive primary afferents, and underpins the mechanism for capsaicin-induced burning pain. Paradoxically, capsaicin has long been used as an analgesic. The development of topical patches and injectable formulations containing capsaicin has led to application in clinical settings to treat chronic pain conditions, such as neuropathic pain and the potential to treat osteoarthritis. More detailed determination of the neurobiological mechanisms of capsaicin-induced analgesia should provide the logical rationale for capsaicin therapy and help to overcome the treatment's limitations, which include individual differences in treatment outcome and procedural discomfort. Low concentrations of capsaicin induce short-term defunctionalization of nociceptor terminals. This phenomenon is reversible within hours and, hence, likely does not account for the clinical benefit. By contrast, high concentrations of capsaicin lead to long-term defunctionalization mediated by the ablation of TRPV1-expressing afferent terminals, resulting in long-lasting analgesia persisting for several months. Recent studies have shown that capsaicin-induced Ca²⁺/calpain-mediated ablation of axonal terminals is necessary to produce long-lasting analgesia in a mouse model of neuropathic pain. In combination with calpain, axonal mitochondrial dysfunction and microtubule disorganization may also contribute to the longer-term effects of capsaicin. The analgesic effects subside over time in association with the regeneration of the ablated afferent terminals. Further determination of the neurobiological mechanisms of capsaicin-induced analgesia should lead to more efficacious non-opioidergic analgesic options with fewer adverse side effects.

Research progress of capsaicin responses to various pharmacological challenges

Capsaicin, a well known vanilloid, has shown evidence of an ample variety of biological effects which make it the target of extensive research ever since its identification. In spite of the fact that capsaicin causes health hazards in quite a few ways, yet, the verity cannot be ignored that capsaicin has several therapeutic implications. In patients with hypersensitive bladders, vesical instillation of 1 mM capsaicin markedly improved urinary frequency and urge incontinence. Again, administration of capsaicin favors an augmentation in lipid mobilization and a decrease in adipose tissue mass. Topical capsaicin cream as well decreases postsurgical neuropathic pain and is preferred by patients over a placebo among other therapies. Several in vitro studies have revealed that capsaicin results in growth arrest in some transformed cell lines. Furthermore, capsaicin has been proven to be an undeniably exciting molecule and remains a valuable drug for alleviating pain and itch. It has been recognized that capsaicinoids are the most potential agonists of capsaicin receptor (TRPV1). However, vanilloids could exert the beneficial effects not only through the receptor-dependent pathway but also through the receptor-independent one. The involvement of serotonin, neuropeptide Substance P and somatostatin in the pharmacological actions of capsaicin has been expansively investigated. Better understanding of the established TRPV1 receptor mechanism as well as exploring other possible receptor mechanism may publicize other new clinical efficacies of capsaicin. Further, clinical studies are required in several of these conditions to establish the efficacy of capsaicin.

Skin Matters: A Review of Topical Treatments for Chronic Pain. Part Two: Treatments and Applications

In Part One of this two-part series, we discussed skin physiology and anatomy as well as generalities concerning topical analgesics. This modality of therapy has lesser side effects and drug-drug interactions, and patients tolerate this form of therapy better than many oral options. Unfortunately, this modality is not used as often as it could be in chronic pain states, such as that from neuropathic pain. Part Two discusses specific therapies, local anesthetics, and other drugs, as well as how a clinician might use specific aspects of a patient's neuropathic pain presentation to help guide them in the selection of a topical agent.

Late effects of breast cancer treatment and potentials for rehabilitation

BACKGROUND

Breast cancer is the most frequent malignant disease among women world wide. Survival has been improving leading to an increasing number of breast cancer survivors, in the US estimated to about 2.6 million.

MATERIAL AND METHODS

The literature was reviewed with focus on data from the Nordic countries.

RESULTS

Local therapies such as breast cancer surgery and radiotherapy may cause persistent pain in the breast area, arm, and shoulder reported by 30-50% of patients after three to five years, lymphedema in 15-25% of patients, and restrictions of arm and shoulder movement in 35%. Physiotherapy is the standard treatment for the latter while no pain intervention trials have been published. Chemotherapy may cause infertility and premature menopause, resulting in vasomotor symptoms, sexual dysfunction, and osteoporosis, which are similar to the side effects of endocrine treatment in postmenopausal women. Awareness of cardiotoxicity is needed since anthracyclines, trastuzumab, and radiotherapy can damage the heart. Breast cancer survivors have an increased risk of a major depression and far from all receive adequate anti-depressive treatment. Other psychological symptoms include fear of recurrence, sleep disturbances, cognitive problems, fatigue, and sexual problems.

DISCUSSION

To improve rehabilitation, specific goals have to be formulated into national guidelines and high priority directed towards research into developing and testing new interventions for alleviating symptoms and side effects experienced by breast cancer survivors.

Topical capsaicin. The fire of a 'hot' medicine is reignited

IMPORTANCE OF THE FIELD

Capsaicin and its receptor, TRPV1, occupy a central place in current neurophysiological studies regarding pain transmission and have opened new avenues for understanding the role of transient receptor potential (TRP) receptors in itch processing. Substantial efforts in drug discovery are at present directed at vanilloid receptors for finding new remedies for pain and itch.

AREAS COVERED IN THIS REVIEW

We provide an overview of the major clinical indications of capsaicin, primarily targeting pain and itch of various origins, with an emphasis on the usefulness of capsaicin in treating pruritus and dermatological conditions. In particular, we cover the most relevant findings in recent years, from 2000 onward (although seminal discoveries and studies are discussed irrespective of their date of publication if deemed essential for understanding capsaicin's actions).

WHAT THE READER WILL GAIN

Readers are offered a broad perspective on the areas of clinical application of capsaicin, emphasizing its usefulness in the treatment of neurophatic pain and pruritus of various origins.

TAKE HOME MESSAGE

Capsaicin has been proven a truly exciting molecule and remains a valuable drug for alleviating pain and itch, widely surpassing its role as a simple spicy ingredient.

NGX-4010, a high-concentration capsaicin patch, for the treatment of postherpetic neuralgia: a randomised, double-blind study

BACKGROUND

The limitations of current treatments for postherpetic neuralgia (PHN) have led to the investigation of localised, non-systemic alternatives. NGX-4010, a high-concentration (8%) capsaicin dermal patch, was developed to treat patients with neuropathic pain. We report the results of a randomised, double blind, 12-week study of the efficacy and safety of one application of NGX-4010 in patients with PHN.

METHODS

In this multicentre, double-blind, parallel-group trial, 402 patients were randomly assigned to one 60-min application of NGX-4010 (640 microg/cm(2) [8% capsaicin]) or a low-concentration capsaicin control patch (3.2 microg/cm(2) [0.04% capsaicin]). Patients were aged 18-90 years, had had postherpetic neuralgia for at least 6 months, and had an average baseline numeric pain rating scale (NPRS) score of 3 to 9. The primary efficacy endpoint was percentage change in NPRS score from baseline to weeks two to eight. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00115310.

FINDINGS

Patients who were randomly assigned to NGX-4010 (n=206) had a significantly greater reduction in pain during weeks two to eight than did patients who had the control patch (n=196). The mean changes in NPRS score were -29.6%vs -19.9% (difference -9.7%, 95% CI -15.47 to -3.95; p=0.001). 87 (42%) patients who received NGX-4010 and 63 (32%) controls had a 30% or greater reduction in mean NPRS score (odds ratio [OR] 1.56, 95% CI 1.03 to 2.37; p=0.03). The patients who had NGX-4010 had significant improvements in pain during weeks two to 12 (mean change in NPRS score -29.9%vs -20.4%, difference -9.5, -15.39 to -3.61; p=0.002). Transient blood pressure changes associated with changes in pain level were recorded on the day of treatment, and short-lasting erythema and pain at the site of application were common, self-limited, and generally mild to moderate in the NGX-4010 group and less frequent and severe in the controls.

INTERPRETATION

One 60-min application of NGX-4010 provided rapid and sustained pain relief in patients with postherpetic neuralgia. No adverse events were associated with treatment except for local reactions at the site of application and those related to treatment-associated pain.

An update on the pharmacological management of post-herpetic neuralgia and painful diabetic neuropathy

Neuropathic pain is a persistent pain condition that develops secondary to nerve injury. The two most common types of peripheral neuropathic pain are post-herpetic neuralgia (PHN) and painful diabetic neuropathy (PDN). Amitriptyline, nortriptyline, desipramine and imipramine are TCAs that have been shown to be effective for the symptomatic relief of PHN and PDN. Serotonin noradrenaline reuptake inhibitors (SNRIs) such as venlafaxine and duloxetine have been shown to be very promising for the treatment of PDN with fewer adverse effects than TCAs. Selective serotonin reuptake inhibitors (SSRIs) were shown in a number of studies to have some efficacy in relieving PDN-related pain, yet other studies of the SSRIs have demonstrated conflicting outcomes. Most of the older antiepileptic studies were performed in patients with PDN; consequently, little is known about the efficacy of these drugs in patients with PHN. Carbamazepine, phenytoin and valproic acid were shown to be effective in ameliorating PDN-related pain. Other antiepileptic agents, including lamotrigine, oxcarbazepine and topiramate, have demonstrated some beneficial effects for the treatment of PDN, although they were also found to be ineffective in some PDN studies. alpha2delta Ligands such as gabapentin and pregabalin have been proven to be effective for the treatment of PHN and PDN in a number of large placebo-controlled trials. These drugs are useful not only in relieving pain but also in improving quality of life. Although the use of opioids for the treatment of neuropathic pain is controversial, a number of studies support the efficacy and safety of opioids in the treatment of neuropathic pain. Of these, oxycodone and tramadol have been shown to be superior to placebo for the treatment of PHN and PDN. A number of small studies have shown that dextromethorphan was effective in patients with PDN but not in patients with PHN. Topical agents such as lidocaine 5% patches and topical capsaicin are useful in ameliorating pain in patients with PHN but these agents are unsatisfactory for use as a sole agent. Although a number of drug treatments are available for the symptomatic relief of neuropathic pain symptoms, these agents do not provide satisfactory relief in all patients. For these patients, other treatment alternatives such as combination drug therapy that produces pain relief via distinctly different mechanisms may be successful. The purpose of this review is to compare the efficacy and limitations of currently available pharmacological treatments for the symptomatic relief of PHN and PDN, and to discuss the potential of combination therapy in PHN and PDN.

Topical amitriptyline and ketamine in neuropathic pain syndromes: an open-label study

Twenty eight subjects with refractory, moderate to severe peripheral neuropathic pain participated in an open label prospective trial examining perceived analgesic effect, patient satisfaction, and safety of topical amitriptyline 2%/ketamine 1% cream. Outcome measures included an 11-point numerical rating scale for pain intensity (NRS-PI), a 5-point satisfaction scale, blood chemistry screen, drug and metabolite levels, urinalyses, electrocardiogram (ECG), and physical examination. Adverse events were monitored. Twenty-one subjects completed the trial. At 6 months, subjects reported an average long-term reduction in pain of 34% (standard deviation [SD] = 37%); 5 subjects (25%) achieved 50% or greater reduction in pain and 1 subject (5%) achieved 100% reduction in pain. At 12 months, the average reduction in pain was 37% (SD = 40%); 7 subjects (40%) achieved 50% or greater pain reduction. At the end of the study, 89% of subjects rated their satisfaction as 3/5 or greater and 2 subjects (10%) were pain free. Minimal adverse events were reported and there were no serious medication related adverse events. Blood levels revealed minimal systemic absorption. In conclusion, topical 2% amitriptyline/ 1% ketamine cream was associated with long-term reduction (6-12 months) in perceived pain, moderate to complete satisfaction, and was well tolerated in treatment of neuropathic pain. There was no significant systemic absorption of amitriptyline or ketamine.

PERSPECTIVE

This study demonstrates that topical 2% amitriptyline/1% ketamine, given over 6-12 months, is associated with long-term perceived analgesic effectiveness in treatment of neuropathic pain. Antidepressants and ketamine both produce multiple pharmacologic effects that may contribute to peripheral analgesia; such actions include block of peripheral N-methyl-D-aspartate receptors, local anesthetic properties, and interactions with adenosine systems.

The pharmacotherapy of chronic pain: a review

The past two decades have contributed a large body of preclinical work that has assisted in our understanding of the underlying pathophysiological mechanisms that cause chronic pain. In this context, it has been recognized that effective treatment of pain is a priority and that treatment often involves the use of one or a combination of agents with analgesic action. The current review presents an evidence-based approach to the pharmacotherapy of chronic pain. Medline searches were done for all agents used as conventional treatment in chronic pain. Published papers up to June 2005 were included. The search strategy included randomized, controlled trials, and where available, systematic reviews and meta-analyses. Further references were found in reference sections of papers located using the above search strategy. Agents for which there were no controlled trials supporting efficacy in treatment of chronic pain were not included in the present review, except in cases where preclinical science was compelling, or where initial human work has been positive and where it was thought the reader would be interested in the scientific evidence to date.

Topical agents for the treatment of chronic pain

Unlike systemic analgesics, topical analgesics exert their analgesic activity locally and without significant systemic absorption. This is in contrast to transdermal analgesics, which require systemic absorption for clinical benefit. The mechanism of action of a particular topical analgesic is unique to the specific medication being used as a topical analgesic. Topical analgesics have been studied in an increasing number of painful clinical conditions, and the results of some of these studies are summarized in this article. The potential role of topical analgesics acting peripherally in affecting the central processing of pain as well as painful states considered to be "central," not "peripheral," also are reviewed.

Use of Herbal Therapies to Relieve Pain: A Review of Efficacy and Adverse Effects

To find holistic treatment with effective pain relief and few side effects, Americans spend billions of dollars annually on complementary and alternative medicine, including herbal therapies. Despite extensive use, the lack of regulatory scrutiny of these herbal supplements contributes to the paucity of reliable clinical data assessing their efficacy and safety. This review summarizes the existing studies investigating the efficacy of herbal therapies as a treatment for pain. Possible side effects, potential drug-herb interactions, and information about common herbal therapies are also summarized. MEDLINE, AMED, and the Cochrane Library databases were searched for the period from January 1966 to June 2005. Uses, dosages, routes of administration, and side effects were summarized. Strength of empirical evidence also was evaluated. This review found few well-controlled clinical studies. Furthermore, these studies documented limited efficacy of herbal therapies to treat pain. The information presented here may be used to further educate nurses and patients on the use of herbal therapies as well as direct future research efforts.

Pharmacologic management of neuropathic pain

The mechanisms underlying the pathogenesis of neuropathic pain are complex but are gradually coming to light. Agents that have been found effective in a variety of neuropathic pain conditions include drugs that act to modulate (a) sodium or calcium channels, (b) N-methyl-D-aspartate receptors, (c) norepinephrine or serotonin reuptake, (d) opioid receptors, and (e) other cellular processes. Clinical trials have primarily evaluated these treatments for postherpetic neuralgia and painful diabetic neuropathy, the two most common types of neuropathic pain. Nonetheless, the identification of effective treatment regimens remains challenging, often because multiple mechanisms may be operating in a given patient giving rise to the same symptom. Alternatively, a single mechanism may be responsible for multiple symptoms. Currently available diagnostic tools are inadequate to determine the best treatment using a mechanism-based model. Clinically, drug treatment of neuropathic pain is often a matter of treatment trials. This article presents a summary of available clinical information on first-line and lesser-known treatments for neuropathic pain.

Surgical treatment of superficial peroneal neuroma

BACKGROUND

Several techniques have been described for the surgical treatment of symptomatic superficial peroneal neuromas, including transection of the nerve with burial in muscle or bone to prevent recurrence.

METHODS

We compared in 27 consecutive patients the results of transection and burial of the proximal peroneal nerve stump into muscle (group A) with results of transection and burial of the proximal stump into bone (group B).

RESULTS

The perceived pain relief and improvement in mean pain score were significantly higher (p < .05) in group B than in group A. In addition, four patients in group A required revision neurotomy compared to none in group B.

CONCLUSION

For symptomatic superficial peroneal neuromas, transection with transposition of the proximal nerve stump into bone provides superior results compared with those of neurotomy with transposition of the proximal stump into muscle.

Targeted peripheral analgesics therapy for neuropathic pain

The term targeted peripheral analgesics has been suggested to describe analgesics with a mechanism of action that appears to be primarily through reducing pain transmission within the peripheral nervous system. Key differences between targeted peripheral (topical) and systemic analgesics and the difference between topical and transdermal analgesics are discussed in this article. A review of the clinical conditions, which have been reported to respond to targeted peripheral analgesics, also is described in detail.

[Reduction of chronic pain for non-postherpetic peripheral neuropathies after topical treatment with a lidocaine patch]

INTRODUCTION

To clarify whether the therapeutic indication for a lidocaine patch to treat postherpetic neuralgia can be extended to include other focal peripheral neuropathic pain syndromes, we performed a subgroup analysis of a placebo-controlled, double-blind randomized study.

METHODS

The study included 16 patients with focal peripheral painful neuropathies of non-herpetic origin, pain intensity > or =40 mm (VAS), and a stable pain medication. The patients received either the lidocaine patch 5% for 1 week or a placebo patch for 12 h daily according to a crossover design. Persistent pain, mechanical allodynia, and adverse events were assessed daily by the patients. Additionally, the pain perception test, the list of physical complaints, the depression test, and the health-related quality of life (SF-36) were used. Of the enrolled patients, 12 were statistically analyzed.

RESULTS

Persistent pain was reduced by the lidocaine patch almost significantly and allodynia was reduced significantly in comparison to the placebo patch. Scores for physical complaints improved significantly with the lidocaine patch. Only mild focal skin irritations occurred.

CONCLUSIONS

As an adjuvant medication, the lidocaine patch is effective and safe for reducing chronic pain and physical complaints in focal non-herpetic neuropathies.

Topical treatments for pain

Topical analgesics exert their analgesic benefit locally and without significant systemic absorption. The mechanism of the topical analgesic is unique to the specific medication. Key differences between topical and transdermal analgesics are discussed in this article. A new term, targeted peripheral analgesics, has been suggested to replace the term topical analgesics, but is not in widespread use. Topical analgesics have been studied in an increasing number of painful clinical conditions; the results of many of these studies are summarized in this review. Recent data suggest that at least one topical analgesic, although applied peripherally, may result in central nervous system alterations of pain processing.

Pharmacological treatments for persistent non-malignant pain in older persons

Persistent non-malignant pain is common, often neglected and under-treated among older persons. Some older adults do not complain because they consider chronic pain to be a characteristic of normal aging. Physicians have concerns regarding adverse effects of pharmacological treatment. The model of the World Health Organization for treatment of cancer pain is generally accepted and also recommended for persistent non-cancer pain. Furthermore, non-pharmacological treatment should complement drug treatment whenever possible. An initial assessment and possible treatment of underlying causes of pain are pertinent. Modern pharmacological pain management is based on non-opioid and opioid analgesics. NSAIDs are among the most widely prescribed class of drugs in the world. The new cyclo-oxygenase-2 inhibitors such as celecoxib and rofecoxib offer an alternative for the treatment of mild-to-moderate pain in patients with a history of gastric ulcers or bleeding. Paracetamol (acetaminophen) is being used widely for the management of mild pain across all age groups as it has moderate adverse effects at therapeutic dosages. For moderate pain, a combination of non-opioid analgesics and opioid analgesics with moderate pain relief properties (e.g. oxycodone, codeine, tramadol and tilidine/naloxone) is recommended. For severe pain, a combination of non-opioid analgesics and opioid analgesics with strong pain relief properties (e.g. morphine, codeine) is recommended. The least toxic means of achieving systemic pain relief should be used. For continuous pain, sustained-release analgesic preparations are recommended. Drugs should be given on a fixed time schedule, and possible adverse effects and interactions should be carefully monitored. Adjuvant drugs, such as antidepressants or anticonvulsants, can be very effective especially in the treatment of certain types of pain, such as in diabetic neuropathy. Effective pain management should result in decreased pain, increased function and improvement in mood and sleep.

Efficacy of lidocaine patch 5% in the treatment of focal peripheral neuropathic pain syndromes: a randomized, double-blind, placebo-controlled study

Peripheral neuropathic pain syndromes (PNPS) are difficult to treat because commonly used analgesics are often ineffective when, for example, touch-evoked allodynia, hyperalgesia, and pain paroxysms are present. To investigate whether lidocaine patch 5% treatment is also effective in postherpetic neuropathy (PHN) and in other PNPS, 40 patients with various forms and localizations of PNPS completed a prospective, randomized, placebo-controlled, two-way, cross-over study in three medical hospitals. Patients suffering from pain in a localized skin area with intensity above 40 mm visual analog scale (VAS) and a stable consumption of pain medication were included in this study. The study was divided into four phases: 3-day run-in phase, treatment phase 1, wash-out period, and treatment phase 2, each lasting 1 week. At the discretion of the patients, up to four patches (covering a maximum of 560 cm2) were applied onto the maximally painful area for 12 consecutive hours daily, always either by day or at night. Throughout the four phases, ongoing pain, allodynia, quality of neuropathic symptoms, quality of sleep, and adverse events were assessed. When, after the wash-out period, the pain intensity scores did not return to the pre-treatment values (+/-20%), these patients were excluded from the study. The present study revealed that, as an add-on therapy, the lidocaine patch 5% was clearly effective in reducing ongoing pain (P=0.017) and allodynia (P=0.023) during the first 8 h after application and that the patches also worked well over a period of 7 days (P=0.018) in diverse focal PNPS. Calculation of the numbers needed to treat (NNT) to obtain one patient with more than 50% relief of ongoing pain revealed that the NNT of 4.4 in the present study compared reasonably well with other studies of PHN, such as topically applied capsaicin (NNT: 5.3-infinity) or systemic treatment with gabapentin (NNT: 3.2-5.0).

A pilot study examining topical amitriptyline, ketamine, and a combination of both in the treatment of neuropathic pain

OBJECTIVE

The involvement of ongoing peripheral activity in the generation of nociceptive input in neuropathic pain suggests that topical drug delivery may be useful as a treatment strategy. This is a pilot study providing initial information regarding the use of novel topical preparations containing amitriptyline (AMI), ketamine (KET), and a combination of both in the treatment of neuropathic pain.

METHODS

The study design included a 2 day randomized, double blind, placebo controlled, 4 way cross-over trial of all treatments, followed by an open label treatment phase using the combination cream for 7 days. Twenty volunteers with chronic neuropathic pain were randomly assigned to treatment order and applied 5 mls of each topical treatment (1% AMI, 0.5% KET, combination AMI 1%/KET 0.5%, and placebo) for 2 days. Measures of pain at the end of each block included the short form McGill Pain Questionnaire (MPQ) and visual analog scales (VAS) for present pain intensity and pain relief. Eleven subjects who judged subjective improvement from any treatment in the initial trial entered the open-label trial and used the combination cream for 7 days. Pain levels were recorded daily using the same measures. Blood levels for amitriptyline and ketamine were performed at 7 days to determine whether systemic absorption had occurred.

RESULTS

There was no statistically significant difference from placebo after 2 days for any treatment during the double blind component of the trial. In the 11 subjects who used the combination cream, there was a statistically significant effect, with subjects reporting significantly greater analgesia by days 3 to 7 according to measures of pain and pain relief. Blood levels revealed that there was no significant systemic absorption of amitriptyline or ketamine. Only 2 subjects experienced side effects; these were minor and did not lead to discontinuation of the cream.

CONCLUSION

This pilot study demonstrated a lack of effect for all treatments in the 2 day double blind placebo controlled trial, followed by analgesia in an open label trial in a subgroup of subjects who chose to use the combination cream for 7 days. Blood analysis revealed no significant systemic absorption of either agent after 7 days of treatment, and creams were well tolerated. A larger scale randomized trial over a longer interval is warranted to examine further effects observed in the open label trial.

Nonopioid and adjuvant analgesics in chronic pain management: strategies for effective use

Nonopioid and adjuvant analgesics encompass a huge range of heterogenous drugs that differ chemically and mechanistically. These drugs generally are prescribed for mild-to-moderate pain, as coanalgesics for severe pain, or to target specific pain-generating mechanisms. This article provides an overview of some of the more commonly used nonopioid and adjuvant analgesics used to treat chronic pain, including salicylates, acetaminophen, nonsteroidal anti-inflammatory drugs, tricyclic antidepressants, anticonvulsants, N-Methyl-D-Aspartate receptor antagonists, lidocaine, skeletal muscle relaxants, and topical analgesics.

Pharmacologic therapies for neck pain

A variety of drug types are available for the treatment of pain. Significant relief of acute neck pain is usually achievable. Treatment of chronic neck pain requires a more comprehensive rehabilitation approach combined with judicious use of medications. Research on the development of analgesics that affect other neurotransmitter systems and that have fewer side effects is currently underway.

Topical and peripherally acting analgesics

Acute nociceptive, inflammatory, and neuropathic pain all depend to some degree on the peripheral activation of primary sensory afferent neurons. The localized peripheral administration of drugs, such as by topical application, can potentially optimize drug concentrations at the site of origin of the pain, while leading to lower systemic levels and fewer adverse systemic effects, fewer drug interactions, and no need to titrate doses into a therapeutic range compared with systemic administration. Primary sensory afferent neurons can be activated by a range of inflammatory mediators such as prostanoids, bradykinin, ATP, histamine, and serotonin, and inhibiting their actions represents a strategy for the development of analgesics. Peripheral nerve endings also express a variety of inhibitory neuroreceptors such as opioid, alpha-adrenergic, cholinergic, adenosine and cannabinoid receptors, and agonists for these receptors also represent viable targets for drug development. At present, topical and other forms of peripheral administration of nonsteroidal anti-inflammatory drugs, opioids, capsaicin, local anesthetics, and alpha-adrenoceptor agonists are being used in a variety of clinical states. There also are some clinical data on the use of topical antidepressants and glutamate receptor antagonists. There are preclinical data supporting the potential for development of local formulations of adenosine agonists, cannabinoid agonists, cholinergic ligands, cytokine antagonists, bradykinin antagonists, ATP antagonists, biogenic amine antagonists, neuropeptide antagonists, and agents that alter the availability of nerve growth factor. Given that activation of sensory neurons involves multiple mediators, combinations of agents targeting different mechanisms may be particularly useful. Topical analgesics represent a promising area for future drug development.

Targeted topical peripheral analgesics in the management of pain

The term "targeted peripheral analgesics" has been developed to describe analgesics whose mechanism of action appears to be primarily through reducing pain transmission within the peripheral nervous system. Key differences between targeted peripheral and systemic analgesics and the difference between topical and transdermal analgesics are discussed. A review of the clinical conditions that have reportedly responded to targeted peripheral analgesics is described in detail in this article.

Intra-ureteric capsaicin in loin pain haematuria syndrome: efficacy and complications

OBJECTIVE

To evaluate the safety and efficacy of intra-ureteric capsaicin for loin pain haematuria syndrome (LPHS).

PATIENTS AND METHODS

In an open prospective pilot study, four middle-aged patients (three women and one man) with LPHS resistant to therapies such as splanchnic nerve block, psychological treatment or renal autotransplantation (one) were assessed. An intra-ureteric infusion of capsaicin (30 mg/100 mL of 30% alcohol in saline) for 30 min with bladder irrigation was administered under general anaesthesia, with a subsequent intravenous patient-controlled narcotic analgesic pump for pain control. Double-concentration capsaicin was used for second infusions, if necessary when the response to the earlier infusion was inadequate or incomplete.

RESULTS

The first patient had experienced reduced pain levels for the first 3 months only, with no benefit from the subsequent treatments with higher doses of capsaicin (60 mg). The second patient with recurrent pain in an autotransplanted kidney had no benefit from either a 30 or 60 mg capsaicin infusion a month apart, but developed a fibrotic stricture at the transplant pelvi-ureteric junction, requiring pyelocystoplasty. The third patient with concurrent depression had no benefit from a 30-mg infusion of capsaicin. The fourth patient experienced no pain relief from a 30 mg infusion of capsaicin but developed proteinuria secondary to mesangial proliferative glomerulonephritis, ureteric inflammation needing stenting within 7 days of treatment and subsequently nephrectomy for a nonfunctioning kidney at 3 months.

CONCLUSION

Intra-ureteric capsaicin was neither effective nor safe in LPHS; the contribution of the alcohol diluent cannot be excluded.

Nerve injuries to the foot and ankle in the industrial setting

Nerve injuries of the foot and ankle are among the most difficult to diagnose and treat. With the added influences of potential secondary gain and poor motivation of the work injured patient, these injuries can be taxing and frustrating to manage in the acute or chronic setting. This article reviews the neuroanatomy, mechanisms of injury, diagnosis and management of these injuries with specific reference to the patient injured in the industrial setting.

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.

Pain in the nursing home

The treatment of pain in the nursing home setting continues to present several unique and challenging problems. Increasingly, studies are focusing on the large number of elderly with important pain problems in long-term care. The inclusion of pain as an area of clinical focus in the Minimum Data Set has fueled interest in this problem and will provide solid data for future study. Researchers are attempting to establish reliable and valid data using standardized assessment tools previously validated in younger adults and are attempting use of traditional and cutting-edge assessment tools in cognitively impaired patients. Assessment is being linked to innovative interventions in noncommunicative, cognitively impaired residents using primary care nurses who best know these patients to decipher "normal" from "abnormal" behavior. The application of available pharmacologic interventions are more challenging because of the higher incidence of side effects in the elderly; part of this problem is the result of the decreased hepatic metabolism and renal clearance present in older patients. The nursing home environment has limited resources that can create logistical concerns in terms of diagnosis and treatment but also can positively limit overly invasive modalities. This article explores these issues and offers suggestions for the appropriate assessment and management of pain in long-term care residents.

The effects of capsaicin cream on prostaglandin-induced allodynia

Although intradermal injection of capsaicin produces acute pain and secondary hyperalgesia, long-term topical application of capsaicin cream has been used as a medication for pain relief in various pain conditions. We previously reported that intrathecal administration of prostaglandin (PG) E(2) and PGF(2alpha) into mice induced touch-evoked pain (allodynia) through capsaicin-sensitive and capsaicin-insensitive afferent fibers, respectively. To clarify the mechanism of an analgesic effect by capsaicin cream, here we applied it to the tail and hind paws of mice and investigated its effects on PGE(2)- and PGF(2alpha)-induced allodynia. Twenty-four-hour pretreatment of mice with 0.025% or 0.05% capsaicin cream markedly alleviated allodynia induced by PGE(2), but not by PGF(2alpha). These results suggest that the topical application of capsaicin cream modulates capsaicin-sensitive afferents and ameliorates allodynia evoked by PGE(2) at the spinal level.

IMPLICATIONS

Topical application of capsaicin cream alleviates touch-evoked pain induced by the intrathecal administration of prostaglandin E(2). This study may provide a rationale for the use of capsaicin cream as a therapeutic drug for pain relief.

Churg-Strauss syndrome: outcome and long-term follow-up of 32 patients

OBJECTIVES

To study the clinical spectrum and evolution of Churg-Strauss syndrome in order to assess the clinicopathological features of the disease, the response to treatment and the long-term outcome.

METHODS

Thirty-two patients with proven allergic and granulomatous angiitis (Churg-Strauss syndrome) and followed up at a single institution were evaluated. They were recruited between 1977 and 1999 from internal medicine departments. Data were obtained retrospectively from medical files in 15 cases and prospectively, using a standardized form, for the remaining patients.

RESULTS

All patients had asthma and hypereosinophilia. The lungs, skin and peripheral nervous system were the organs most frequently involved. Antineutrophil cytoplasmic antibodies with antimyeloperoxidase specificity (MPO-ANCA) were detected in 77.8% of tested patients but they were not useful for monitoring disease activity. Extravascular granulomas were rarely seen in tissue biopsies. Forty per cent of the patients were treated with steroids alone. Immunosuppressive agents were added to the treatment when severe neurological, cardiac or gastrointestinal involvement was present. The outcome and long-term survival were good. Clinical relapse was rare after the first year of therapy. Dysaesthesiae of the distal limbs, neurophatic pain and cardiac failure were the most frequent sequelae.

CONCLUSIONS

Churg-Strauss syndrome is a rare disorder characterized by hypereosinophilia and systemic vasculitis occurring in patients with asthma and allergic rhinitis. Vasculitis commonly affects the lungs, skin and peripheral nervous system. Outcome and long-term survival is usually good with steroids alone or in combination with immunosuppressive agents. The syndrome has a low mortality rate compared with other systemic vasculitides.

Pain in nursing home residents: management strategies

Pain is prevalent and undertreated in nursing home residents, despite the existing wide array of effective pharmacological and nonpharmacological treatment modalities. In order to improve the quality of life of these vulnerable individuals, practitioners require education about the correct approach to assessment and management. Assessment should be comprehensive, taking into account the basic underlying pathology (e.g. osteoarthritis, osteoporosis, peripheral neuropathy, fibromyalgia, cancer) as well as other contributory pathology (e.g. muscle spasm, myofascial pain) and modifying comorbidities (e.g. depression, anxiety, fear, sleep disturbance). Pharmacological management should be guided by a stepped-care approach, modelled after that recommended by the World Health Organization for treatment of cancer pain. Nonopioid and opioid analgesics are the cornerstone of pharmacological pain management. Tricyclic antidepressants and anticonvulsants can be very effective for the treatment of certain types of neuropathic pain. In addition to treating the pain per se, attention should be given to prevention of disease progression and exacerbation, as maintaining function is of prime importance. Nursing home residents with severe dementia challenge the practitioner's pain assessment skills; an empirical approach to treatment may sometimes be warranted. The success of treatment should be measured by improvement in pain intensity as well as physical, psychosocial and cognitive function. Effective pain management may impact any or all of these functional domains and, therefore, substantially improve the nursing home resident's quality of life.

Antinociceptive activity of ricinoleic acid, a capsaicin-like compound devoid of pungent properties

The antinociceptive effect of ricinoleic acid ([R-(Z)]-12-hydroxy-9-octadecenoic acid) in comparison with capsaicin (trans-8-methyl-N-vanillyl-6-nonenamide) has been investigated in several "in vivo" tests. Acute topical application of capsaicin, but not ricinoleic acid, produced by itself an hyperalgesic effect detected as a decrease in paw withdrawal latency in response to a painful (heat) stimulus in mice. Capsaicin, but not ricinoleic acid at any dose tested, showed an irritant effect in the wiping test in guinea pig conjunctiva after local application and in the paw licking test in mice after intradermal injection. Whereas acute application of ricinoleic acid or capsaicin decreased paw withdrawal latency to heat in the presence of a pre-existing inflammation (injection of carrageenan in the mouse paw), the repeated local treatment for 8 days with either compounds markedly increased paw withdrawal latency. In a chronic model of inflammation (complete Freund's adjuvant arthritis in mice), the repeated topical and intradermal treatments with both ricinoleic acid and capsaicin increased paw withdrawal latency to heat, the antinociceptive effect of ricinoleic acid being more persistent than that of capsaicin. Antinociceptive effect of 8 days of treatment with ricinoleic acid and capsaicin was observed in acetic acid-induced writhing in mice, capsaicin-induced foot licking in mice and capsaicin-induced wiping movements in guinea pig conjunctiva. A decrease of substance P tissue levels in the mouse paw was found after repeated treatment with ricinoleic acid. In conclusion, ricinoleic acid seems to be a new antinociceptive agent lacking the pungent and acute hyperalgesic properties of capsaicin.

Phantom Tooth Pain: A New Look at an Old Dilemma

The aim of this paper is to review the current knowledge of phantom tooth pain, a neuropathic facial pain disorder, thought to result from peripheral nerve injury. Phantom tooth pain is a deafferentation pain disorder of persistent toothache in teeth that have been denervated (usually by root canal treatment) or pain in the area formerly occupied by teeth prior to their extraction. The pain usually extends to the facial structures adjacent to tissues that have undergone deafferentation. The clinical characteristics, differential diagnosis, epidemiology, and treatment of phantom tooth pain are reviewed. Suggestions for further research include the need for controlled treatment trials and modification of current criteria.

CONCLUSIONS

Phantom tooth pain has much in common with other phantom pain disorders. In the absence of controlled clinical trials specifically directed to phantom tooth pain, treatment should be guided by standards used for other neuropathic pain disorders. Revised diagnostic criteria for phantom tooth pain are proposed.

When there is no benchmark: designing a primary care-based chronic pain management program from the scientific basis up

Managed care has been accused of ignoring the patient with pain. The challenge for a health maintenance organization (HMO) was not just how to deliver state-of-the-art care, but how to deliver it to the 40,000 members who experience chronic pain at a reasonable cost and with enduring outcomes. This article describes how one managed care organization set about improving the care of patients with chronic pain. The article includes the design process, the model implemented, and some suggestions for transfer of this technology to others who might want to explore developing a similar model.

Painful polyneuropathy

Painful polyneuropathy is one of the most common chronic pain syndromes neurologists are asked to assess for diagnostic and therapeutic purposes. This article reviews the most current clinical guidelines, including history, pain assessment, physical examination findings, treatment recommendations, and pathophysiologic pain mechanisms underlying this condition. As a result of recent advances, the understanding and therapy of pain associated with polyneuropathy has evolved over the past several years and will continue to do so in the years to come.

Topical capsaicin as an adjuvant analgesic for the treatment of traumatic amputee neurogenic residual limb pain

The treatment of amputee residual limb pain can at times be a challenge for the physician. Occasionally, traditional analgesic medication regimens cannot be used or are ineffective in relieving the pain. Topical capsaicin cream has been a beneficial adjuvant medication in the treatment of some painful conditions. The authors present three patients with traumatic upper limb amputations where topical capsaicin cream was of benefit in the treatment of neurogenic residual limb pain. The hope is that these cases will increase awareness of the potential use of capsaicin cream as an adjuvant analgesic in patients with residual limb pain. Common causes of residual limb pain and the pharmacology of capsaicin cream are discussed.

The role of plant-derived drugs and herbal medicines in healthcare

Many of our present medicines are derived directly or indirectly from higher plants. While several classic plant drugs have lost much ground to synthetic competitors, others have gained a new investigational or therapeutical status in recent years. In addition, a number of novel plant-derived substances have entered into Western drug markets. Clinical plant-based research has made particularly rewarding progress in the important fields of anticancer (e.g. taxoids and camptothecins) and antimalarial (e.g. artemisinin compounds) therapies. In addition to purified plant-derived drugs, there is an enormous market for crude herbal medicines. Natural product research can often be guided by ethnopharmacological knowledge, and it can make substantial contributions to drug innovation by providing novel chemical structures and/or mechanisms of action. In the end, however, both plant-derived drugs and crude herbal medicines have to take the same pharmacoeconomic hurdle that has become important for new synthetic pharmaceuticals.

[Review of current pharmacologic treatment of pain]

Pain is the main reason prompting patients to consult their physicians. In acute conditions, pain has a very particular significance as a warning sign, enabling the physician to attempt a diagnosis. Nevertheless, its detrimental effect upon the individual (even in the case of acute pain) and its cost to society are now widely acknowledged. There can be no doubt about the physical component of pain, but the psychological and social aspects should not be ignored, particularly in the case of chronic pain. There is no single therapeutic approach to pain and, more often than not, successful treatment comprises a combination of several. Pharmacological treatments are undeniably the most common approach. In clinical practice, recent advances have been based upon an improved understanding of 'old' substances such as morphine and, at the same time, research continues in the hope of finding the 'ideal' analgesic-effective in most situations but without adverse effects: this appears to be a somewhat utopian arm at present, considering the number of different causes of pain. An improved understanding of the physiological mechanisms of pain has led, within the field of clinical practice, to several methods of differentiating pain. These depend on whether or not pain responds to morphine, or on the type of pain: pain due to an excess of nociception, pain resulting from deafferentation (caused by damage to nerve pathways) in the central or peripheral nervous system and psychogenic (idiopathic) pain. Likewise, there are several different ways of classifying analgesic treatments: according to the intensity of pain, as with use of the WHO ladder (which is based on the notion of steps) for the treatment of cancer pain; according to the presumed physiopathological mechanism and, in particular, the response to morphine, and according to the presumed central or peripheral mechanism of the drugs. In reality, peripherally acting drugs can also have a central mechanism of action, just as drugs known to have a central mechanism of action can also have peripheral activity. As a result, several therapeutic classes have been identified. Firstly NSAIDs, which act by inhibiting the enzymes that synthesise prostaglandins, cyclooxygenases (COX-1, COX-2), but which also act upon lipo-oxygenases: Their efficacy is interesting, although somewhat limited by both their ceiling effect and the frequent adverse gastrointestinal reactions they produce. Specific inhibitors of COX-2 could well reduce the risk of adverse effects. Opioids constitute the first-line treatment for pain, particularly severe pain. There are several classifications for these drugs. Firstly, weak opioids (such as codeine) and strong opioids (such as morphine) are differentiated. Secondly, a distinction is made between pure agonists (such as morphine), partial agonists (such as buprenorphine), agonist-antagonists (such as nalbuphine) and antagonists (such as naloxone). Finally, agents are distinguished on the basis of their chemical structure (synthetic, semi-synthetic or natural derivatives). These molecules act upon different receptors (mu, delta, kappa, sigma) and, although peripheral mechanisms have been described, their activity occurs mainly at spinal and supraspinal levels. They provide a potent analgesic effect but are also responsible for various adverse effects-nausea, vomiting, sedation, constipation and respiratory depression-which seriously limit their use. As long as the indication is appropriate, these drugs should not be withheld because of fear of dependence or abuse. It has been observed that other adjuvant therapeutic approaches, generally used to treat conditions other than pain, provide pain relief in certain situations. These include corticosteroids, which are-widely used in rheumatology and oncology, and antidepressants, which are frequently used to treat chronic pain, especially that with a neuropathic component. Anti-epileptics are also used, particularly for excrutiating