Localized neuropathic pain: an expert consensus on local treatments

Is the Capsaicin 179 mg (8% w/w) Cutaneous Patch an Appropriate Treatment Option for Older Patients with Peripheral Neuropathic Pain?

Introduction

Capsaicin 179 mg (8% weight per weight) cutaneous patch ("capsaicin patch") is a recommended topical treatment for peripheral neuropathic pain (PNP). In older patients, topical treatments may be preferred over systemic treatments, but data specific to the older population are scarce.

Methods

We conducted pooled analyses of multiple clinical trials to evaluate efficacy and safety of capsaicin patch in older patients. The analysis of efficacy included four randomized, double-blind, 12-week studies with similar trial design comparing a single treatment of capsaicin 179 mg cutaneous patch vs low-dose control patch in post-herpetic neuralgia. For the safety evaluation, data were pooled from 18 interventional studies in which capsaicin patch was used in PNP with varying etiologies.

Results

Capsaicin patch had similar analgesic efficacy in elderly (n=582) and non-elderly patients (n=545) in terms of change from baseline to 2-12 weeks in the 11-point numeric pain rating scale (NPRS) score for average pain over the previous 24 hours. In both age groups, decrease in NPRS score was significantly greater with capsaicin patch vs control. Older patients treated with capsaicin patch were significantly more likely than those in the control group to achieve responder status (ie mean decrease in NPRS score from baseline to week 2-12 of at least 30% or ≥2 points): 36.1% vs 27.1% (odds ratio [OR] [95% CI] 1.52 [1.06, 2.18]; P=0.0231) and 33.1% vs 20.9% (OR [95% CI] 1.90 [1.30, 2.78]; P=0.0009) for active treatment vs control group, respectively. Similar proportions of non-elderly patients (n=2,311) and elderly patients (n=537) treated with capsaicin patch experienced treatment-emergent adverse events (TEAEs) (81.6% and 78.1%, respectively) and serious TEAEs (8.2% and 7.2%), with application-site reactions the most common TEAEs in both groups.

Conclusion

The capsaicin patch was equally efficacious and well tolerated in older patients as in younger patients.

Pain as a disease in the new International Classification of Diseases (ICD-11): Latin American expert consensus

Aims: Pain diagnoses in the 10th version of the International Classification of Diseases (ICD-10) did not adequately support the current management of pain. Therefore, we aimed to review the new 11th revision (ICD-11) in order to analyze its usefulness for the management, coding, research and education of chronic pain from a Latin American perspective. Methods: The Latin American Federation of Associations for the Study of Pain convened a meeting of pain experts in Lima, Peru. Pain specialists from 14 Latin American countries attended the consensus meeting. Results: In ICD-11, chronic pain is defined as pain that persists or recurs longer than 3 months and is subdivided into seven categories: chronic primary pain and six types of chronic secondary pain. Chronic primary pain is now considered a disease in itself, and not a mere symptom of an underlying disease. Conclusion: The novel definition and classification of chronic pain in ICD-11 is helpful for better medical care, research and health statistics. ICD-11 will improve chronic pain management in Latin American countries, for both the pain specialist and the primary care physician.

Exploring the Biomarkers and Potential Mechanisms of Botulinum Toxin Type A in the Treatment of Microglial Inflammatory Activation through P2X7 Receptors based on Transcriptome Sequencing

AIMS

This study aims to explore the potential mechanism by which Botulinum toxin type A (BoNT/ A) inhibits microglial inflammatory activation through P2X7 receptors (P2X7R).

BACKGROUND

BoNT/A is a promising analgesic drug, and previous studies have established that it alleviates Neuropathic Pain (NP) by inhibiting microglial inflammatory activation. This study examined the biomarkers and potential mechanisms by which BoNT/A relieves neuropathic pain by mediating microglial P2X7R and analyzing transcriptome sequencing data from mouse BV-2 microglial cells.

OBJECTIVE

The P2X7R agonist Bz-ATP was used to induce microglial inflammatory activation, whilst RNAseq technology was used to explore the biomarkers and potential mechanisms through which BoNT/A suppresses microglial inflammation.

METHODS

RNA sequencing was performed on three BV-2 cell samples treated with a P2X7R specific activator (Bz-ATP) and three BV-2 cell samples pre-treated with BoNT/A. Only data that successfully passed quality control measures were included in subsequent analysis. Initially, Differentially Expressed Genes (DEGs) were identified from BoNT/A and control samples, followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. Biomarkers were then identified by constructing a Protein- Protein Interaction (PPI) network and utilizing the CytoHubba plug-in in Cytoscape software. Lastly, enrichment analysis and regulatory network analysis were performed to elucidate the potential mechanism of BoNT/A in the treatment of NP.

RESULTS

93 DEGs related to the "cell component size regulation" GO term and enriched in the "axon guidance" KEGG pathway were identified. Subsequently, 6 biomarkers were identified, namely PTPRF, CHDH, CKM, Ky, Sema3b, and Sema3f, which were enriched in pathways related to biosynthesis and metabolism, disease progression, signal transduction, and organelle function, including the "ribosome" and "Wnt signaling pathway." Finally, a competing endogenous RNA (ceRNAs) network was constructed from 6 mRNAs, 66 miRNAs, and 31 lncRNAs, forming a complex relationship network.

CONCLUSION

Six genes (PTPRF, Sema3b, Sema3f, CHDH, CKM, and Ky) were identified as biomarkers of microglial inflammatory activation following BoNT/A treatment. This finding may provide a valuable reference for the relief and treatment of neuropathic pain.

Painful diabetic peripheral neuropathy of the feet: integrating prescription-strength capsaicin into office procedures

Prescription-strength (8%) capsaicin topical system is a US FDA-approved treatment for painful diabetic peripheral neuropathy of the feet. A 30 min application of the capsaicin 8% topical system can provide sustained (up to 3 months) local pain relief by desensitizing and reducing TRPV1-expressing cutaneous fibers. Capsaicin is not absorbed systemically; despite associated application-site discomfort, capsaicin 8% topical system is well tolerated, with no known drug interactions or contraindications, and could offer clinical advantages over oral options. Capsaicin 8% topical system are not for patient self-administration and require incorporation into office procedures, with the added benefit of treatment compliance. This article reviews existing literature and provides comprehensive, practical information regarding the integration of capsaicin 8% topical systems into office procedures.

Ferroptosis: a new regulatory mechanism in neuropathic pain

Neuropathic pain (NP) is pain caused by damage to the somatosensory system. It is a common progressive neurodegenerative disease that usually presents with clinical features such as spontaneous pain, touch-evoked pain, nociceptive hyperalgesia, and sensory abnormalities. Due to the complexity of the mechanism, NP often persists. In addition to the traditionally recognized mechanisms of peripheral nerve damage and central sensitization, excessive iron accumulation, oxidative stress, neuronal inflammation, and lipid peroxidation damage are distinctive features of NP in pathophysiology. However, the mechanisms linking these pathological features to NP are not fully understood. The complexity of the pathogenesis of NP greatly limits the development of therapeutic approaches for NP. Ferroptosis is a novel form of cell death discovered in recent years, in which cell death is usually accompanied by massive iron accumulation and lipid peroxidation. Ferroptosis-inducing factors can affect glutathione peroxidase directly or indirectly through different pathways, leading to decreased antioxidant capacity and accumulation of lipid reactive oxygen species (ROS) in cells, ultimately leading to oxidative cell death. It has been shown that ferroptosis is closely related to the pathophysiological process of many neurological disorders such as NP. Possible mechanisms involved are changes in intracellular iron ion levels, alteration of glutamate excitability, and the onset of oxidative stress. However, the functional changes and specific molecular mechanisms of ferroptosis during this process still need to be further explored. How to intervene in the development of NP by regulating cellular ferroptosis has become a hot issue in etiological research and treatment. In this review, we systematically summarize the recent progress of ferroptosis research in NP, to provide a reference for further understanding of its pathogenesis and propose new targets for treatment.

Pregabalin-Tolperisone Combination to Treat Neuropathic Pain: Improved Analgesia and Reduced Side Effects in Rats

The current treatment of neuropathic pain (NP) is unsatisfactory; therefore, effective novel agents or combination-based analgesic therapies are needed. Herein, oral tolperisone, pregabalin, and duloxetine were tested for their antinociceptive effect against rat partial sciatic nerve ligation (pSNL)-induced tactile allodynia described by a decrease in the paw withdrawal threshold (PWT) measured by a dynamic plantar aesthesiometer. On day 7 after the operation, PWTs were assessed at 60, 120, and 180 min post-treatment. Chronic treatment was continued for 2 weeks, and again, PWTs were measured on day 14 and 21. None of the test compounds produced an acute antiallodynic effect. In contrast, after chronic treatment, tolperisone and pregabalin alleviated allodynia. In other experiments, on day 14, the acute antiallodynic effect of the tolperisone/pregabalin or duloxetine combination was measured. As a novel finding, a single dose of the tolperisone/pregabalin combination could remarkably alleviate allodynia acutely. It also restored the neuropathy-induced elevated CSF glutamate content. Furthermore, the combination is devoid of adverse effects related to motor and gastrointestinal transit functions. Tolperisone and pregabalin target voltage-gated sodium and calcium channels, respectively. The dual blockade effect of the combination might explain its advantageous acute analgesic effect in the present work.

Randomized, Placebo-Controlled, Multicenter Clinical Study on the Efficacy and Safety of Lidocaine Patches in Chinese Patients with Postherpetic Neuralgia

INTRODUCTION

To evaluate the efficacy and safety of lidocaine patches in Chinese patients with postherpetic neuralgia (PHN).

METHODS

Patients were randomized to receive lidocaine patches or placebo every day for 4 weeks. Efficacy endpoints included the decrease of analogue scale score (VAS) value at week 4, 2 and 1 and the percentage of patients that achieved a 30% decrease of VAS value. Safety analyses were conducted as well.

RESULTS

Two hundred forty Chinese patients were randomized. At week 1, lidocaine patch-treated patients had a higher clinical response versus placebo, and at week 4, the mean (SD) decreases of VAS value compared to the baseline were 14.01 (14.35) in the treatment group and 9.36 (12.03) in the placebo group (p = 0.0088). Overall, the safety profile in the treatment group was consistent with that observed in the placebo group [adverse event (AE) incidence rate: 33.33% versus 37.29%, p = 0.5857].

CONCLUSIONS

Lidocaine patches resulted in improved clinical response versus placebo in the treatment of PHN patients and were well tolerated.

[Thermal radiofrequency as an alternative in the treatment of persistent localized neuropathic pain due to entrapment of a collateral nerve of the hand]

Localized neuropathic pain (LNP) is a relatively common cause of musculoskeletal pain, which can be present in up to 60% of neuropathic pain conditions. Its appearance can be associated with numerous pathologies (herpes, diabetes, etc.). A less common cause would be the direct compression of a peripheral nerve branch. Its diagnosis is usually clinical since complementary tests such as neurophysiological tests do not provide definitive data. As therapeutic measures we have oral analgesics, anticonvulsants, analgesic skin patches and interventional actions, including radiofrequency (RF). Thermal RF consists in the transmission of an electric impulse through a needle reaching a controlled increase in temperature with which a nerve ablative injury is achieved. We present a clinical case where thermal RF of the collateral nerve of the hand is proposed as a therapeutic alternative, whose entrapment is the cause of pain, obtaining a satisfactory clinical improvement.

Successful treatment of notalgia paresthetica with lidocaine 5% medicated plaster: a case report

Notalgia paresthetica (NP) is a sensory neuropathy characterized by chronic, localized pruritus in a circumscribed area on the upper back. Pruritus, frequently resistant to treatment, may be accompanied by pain, paresthesia, allodynia and alloknesis. There is a paucity of data in the NP literature about the use of lidocaine 5% medicated plaster. This case involves a 75-year-old woman with NP and a history of many unsuccessful local or systemic treatments. The patient was treated with lidocaine 5% medicated plaster, while other therapies were progressively retired. After 11 weeks of therapy, a significant reduction in the intensity of itching was achieved and the itching area was reduced. The patient also reported an associated improvement in her quality of life throughout therapy. In conclusion, lidocaine 5% medicated plaster was successful in relieving itching and other symptoms in this case of NP.

Bilateral intraoral traumatic neuroma: Case report of a diagnostic challenge

Oral traumatic neuromas (TrNs) are relatively rare lesions and they originate from a damaged nerve. They present a diagnostic challenge, due to the complex clinical features that may mimic odontogenic, musculoskeletal, and other neuropathic pain conditions. We describe an interesting and challenging case of painful bilateral intraoral lesions in a 56-year-old South Indian female patient who presented with clinical features consistent with TrN lesions bilaterally, in relation to different branches of the trigeminal nerve. The patient had undergone numerous aggressive dental treatments and interventions over the past three decades, with little or no pain relief. Topical treatment with lidocaine gel utilizing a custom-made neurosensory stent rendered the patient significant and sustained pain relief.

Topical Lidocaine for Chronic Pain Treatment

Topical lidocaine is widely used in current practice for a variety of pain conditions. This literature review shows that its limited absorption and relative lack of systemic adverse events are an attractive analgesic option for a number of vulnerable patients. Topical lidocaine has been approved by health authorities for the treatment of post-herpetic neuralgia in a number of countries, and studies present some degree of evidence of its efficacy and safety in postsurgical pain, diabetic peripheral neuropathy, carpal tunnel syndrome, chronic lower back pain and osteoarthritis. Topical lidocaine may be a great alternative alone or in addition to systemic drugs and non-pharmacological approaches for an optimized pain management and in multimodal analgesia.

Interest of a standardized hypnotic message for the reduction of pain and anxiety in cancer patients treated by capsaicin patch for neuropathic pain: a randomized controlled trial

BACKGROUND

Neuropathic pain is characterized by spontaneous painful symptoms. Medical therapies include the use of a capsaicin 8% patch (Qutenza®, Grünenthal Gmbh, Germany), and patients may experience a sharp burning sensation at application and removal of the patch. This study aimed to evaluate the impact of playing a standardized hypnosis recording during application, on the pain and anxiety induced by capsaicin treatment.

METHODS

In a randomized, controlled trial, we assessed the benefits of the intervention firstly on pain and secondly on anxiety, as measured using numerical rating scales. All patients had application of the capsaicin patch, including the possibility for the patient to apply a cold patch. Participants were randomly assigned to one of 3 groups, namely the "Standard group" (no intervention), "Hypnosis group", in which a standardized hypnotic message was played during application, or the "Music group" in which relaxing music was played during application of the patch.

RESULTS

Sixty-nine patients were included. Overall, there was no significant difference in pain scores between groups (p = 0.355). Compared to standard application, anxiety was significantly lower in the hypnosis group after application (p = 0.007), with no significant difference between the standard and music arms (p = 0.271), or between the hypnosis and music arms (p = 0.423).

CONCLUSIONS

Listening to a standardized hypnotic message during application of a capsaicin patch was found to significantly lower anxiety. These findings indicate that the use of a hypnotic message can reduce discomfort and warrant its evaluation in other indications of pain or anxiety during treatment procedures.

TRIAL REGISTRATION

NCT02822625 .

Management of Neuropathic Pain in the Geriatric Population

Neuropathic pain is common in the geriatric population. Diagnosis requires a thorough history and physical examination to differentiate it from other types of pain. Once diagnosed, further workup is required to elucidate the cause, including potential reversible causes of neuropathy. When treating neuropathic pain in the elderly, it is important to consider patients' comorbidities and other medications to avoid drug-drug interactions and iatrogenic effects given the physiologic changes of drug metabolism in the elderly. Nonsystemic therapies and topical medications should be considered. Systemic medications should be started at low dose and titrated up slowly with frequent monitoring for adverse effects.

Topical Capsaicin for the Treatment of Neuropathic Pain

BACKGROUND

Neuropathic pain (NP) is an egregious problem worldwide. Due to the side-effects of oral drugs, drugs delivered directly to the affected area of pain are preferred.

OBJECTIVE

Capsaicin, a chemical compound isolated from chili peppers, is used as an analgesic in topical ointments and dermal patches to alleviate pain. Objective of the study is to review the application and functionality of topical capsaicin in treatment of neuropathic pain.

DATA SOURCES

To systematically review capsaicin's functions on NP, we retrieved articles from the PubMed database published in the last ten years.

STUDY ELIGIBILITY CRITERIA

The inclusion criteria were capsaicin and the use of capsaicin for the treatment of NP; on the other hand, articles were excluded according to the mentioned criteria such as abstracts, articles written in any language other than English, incomplete articles, and conference papers.

PARTICIPANTS AND INTERVENTIONS

Out of 265 articles, 108 articles were selected after filtering through the inclusion and exclusion criteria. The data and knowledge currently existing for capsaicin treatment in NP are summarized.

RESULTS

This review indicates that capsaicin effectively improves NP treatment without affecting the motor and large nerve fibres involved in sensory function. Transient receptor potential channel vanilloid type 1 (TRPV1) is the capsaicin receptor expressed in central and peripheral terminals of a sensitive primary nerve cell. Conclusions and implications of key findings: Topical capsaicin has a sensible safety profile and is effective in reducing NP. Therefore, studies over the last decade suggest that capsaicin might be a potential drug for NP treatment.

Expert consensus of the Chinese Association for the Study of Pain on pain treatment with the transdermal patch

Chronic pain lasting more than 3 mo, or even several years can lead to disability. Treating chronic pain safely and effectively is a critical challenge faced by clinicians. Because administration of analgesics through oral, intravenous or intramuscular routes is not satisfactory, research toward percutaneous delivery has gained interest. The transdermal patch is one such percutaneous delivery system that can deliver drugs through the skin and capillaries at a certain rate to achieve a systemic or local therapeutic effect in the affected area. It has many advantages including ease of administration and hepatic first pass metabolism avoidance as well as controlling drug delivery, which reduces the dose frequency and side effects. If not required, then the patch can be removed from the skin immediately. The scopolamine patch was the first transdermal patch to be approved for the treatment of motion sickness by the Food and Drug Administration in 1979. From then on, the transdermal patch has been widely used to treat many diseases. To date, no guidelines or consensus are available on the use of analgesic drugs through transdermal delivery. The pain branch of the Chinese Medical Association, after meeting and discussing with experts and based on clinical evidence, developed a consensus for promoting and regulating standard use of transdermal patches containing analgesic drugs.

Comprehensive Review of Topical Analgesics for Chronic Pain

PURPOSE OF REVIEW

Topical analgesics are a non-opioid option for the treatment of chronic pain conditions including neuropathic pain, musculoskeletal pain, and osteoarthritis. There are many topical medications available; however their efficacy is variable. This article reviews the various topical analgesics, their mechanisms of action, and their efficacy.

RECENT FINDINGS

Studies have found topical NSAIDs are useful in treating acute musculoskeletal pain syndromes (strains and sprains) and show some efficacy in treating hand and knee osteoarthritis (Derry et al. Cochrane Database Syst Rev 5:CD008609, 2017). Topical capsaicin 8% has been shown to be efficacious in the treatment of postherpetic neuralgia, painful diabetic peripheral neuropathy, and HIV-neuropathy (Derry et al. Cochrane Database Syst Rev 1:CD007393, 2017). Topical lidocaine has been widely studied and found to reduce pain in patients with postherpetic neuralgia (Knezevic et al. Pain Manag 7:537-58, 2017). Although many other topical analgesics are available, there is limited data to support the efficacy of other agents. Topical analgesics are a relatively benign treatment for chronic pain conditions including neuropathic pain, musculoskeletal, and myofascial pain. There is evidence to support the use of topical NSAIDs, high concentration topical capsaicin, and topical lidocaine for various painful conditions.

Localised neuropathic pain in the primary care setting: a cross-sectional study of prevalence, clinical characteristics, treatment patterns, quality of life and sleep performance

BACKGROUND

Localised Neuropathic Pain (LNP) is challenging to diagnose and manage in primary care.

OBJECTIVE

To describe clinical characteristics, treatment patterns, quality of life and sleep performance of patients with LNP and estimate its prevalence in primary care.

METHODS

Cross-sectional study in 4 European countries. Patients were identified using a screening tool for LNP. Patients completed the EQ-5D VAS score and Chronic Pain Sleep Inventory (CPSI).

RESULTS

There were 1030 LNP patients for analysis. They presented a median pain intensity of 6.0 (IQR 4.0-7.0) with a median duration of 30.9 months (IQR 12.0-75.3), despite 97% receiving pain treatment. Main sites affected were the limbs (62% upper/58% lower) and spine (41%). Main aetiologies were neuropathic low back pain (47%), post-surgical neuropathic pain (17%), and diabetic poly-neuropathy (12%). Thirty percent received a single analgesic (2% topical), while combinations comprised 43% systemic-systemic, 24% topical-systemic, 1% topical-topical. Medications included NSAIDs (45%), anticonvulsants (38%), WHO step 2 opioids (35%), and topical analgesics (27%). In the previous 6 months, 40% had switched treatment. The mean (SD) EQ-5D VAS score was 58 (22.3) and the mean (SD) EQ-5D summary score (UK tariff) was 0.62 (0.25). Patients had a CPSI mean index of 41/100, and sleeping pills were used by 33% of patients. The standardized prevalence of LNP by age and sex was 2.01% in the general population and 43.3% among chronic pain patients.

CONCLUSIONS

Many LNP patients reported pain intensities of six on a ten-point scale in average for durations longer than 2.5 years, with quality of life and sleep performance affected, with frequent treatment combinations and switches, suggesting suboptimal pain management.

The efficacy and safety profile of capsaicin 8% patch versus 5% Lidocaine patch in patients with diabetic peripheral neuropathic pain: a randomized, placebo-controlled study of south Asian male patients

Aims

Diabetic peripheral neuropathy affects up to 60% of individuals and often leads to foot ulceration and eventual amputation. When oral therapy has failed to achieve pain relief, the first line local treatment is the 5% lidocaine-medicated plaster which provides local relief. Capsaicin 8% patch is considered a promising topical treatment for diabetic peripheral neuropathy. The present study investigated the efficacy, safety and tolerability of capsaicin 8% patch vs 5% lidocaine patch treatments over 24 weeks in South Asian male diabetic patients with established peripheral diabetic neuropathy.

Methods

Analgesic effectiveness was assessed by observing any change in the Numeric Pain Rating Scale (NPRS) score, Brief Pain Inventory (BPI) for painful diabetic peripheral neuropathy (BPI-DPN question 4) and Patient Global Impression of Change (PGIC). All patients received 4% lidocaine gel/cream for 60 min prior to patch application. The trial was probably underpowered, taking into account the smaller than expected number of participants from the calculated 350 sample size required for the whole study. Two hundred ninety-one individuals were divided into three groups based on treatment regimen; Group LL (Lidocaine + Lidocaine), Group LP (Lidocaine + Placebo), Group LC (Lidocaine + Capsaicin). The treatment procedure was conducted once initially and then repeated once at 12 weeks. The patients were followed up on alternate weeks till 24 weeks after the initial treatment.

Results

Group LC experienced a more significant reduction in the average pain intensity (p < 0.05) during the last twenty-four hours. Group LC showed more significant reduction of pain compared to control (p < 0.01), a baseline score of 5.4 ± 1.2 dropped to 3.2 ± 1.5 by week 24 of treatment. The change in mean daily pain intensity was - 2.2 ± 1.5 [95% CI: -2.45, -1.5]. Group LL and LC experienced a significant overall improvement (slightly, much or very much) in the health status during the study. After the second week of the treatment, patient satisfaction scores were 2.1 ± 1.1 in Group LL which increased to 3.2 ± 1.2 by week 24 of treatment. The capsaicin 8% patch appears to be reasonably well tolerated since there were no discontinuations because of serious drug-related treatment emergent adverse event (TEAEs).

Conclusions

The aim of the present study was to assess the efficacy, safety and tolerability of the 8% capsaicin patch in patients with established painful diabetic neuropathy. There was a sustained treatment response to the initial and repeat treatment of the capsaicin 8% patch over the 24 weeks. The study population was very specific so further studies are required to investigate the generalizability of the results for patients experiencing painful diabetic neuropathy. The patch could be considered as an effective long-term treatment option in individuals with painful diabetic neuropathy, particularly those experiencing inadequate pain relief or side effects from systemic therapies.

Neurophysiological Mechanisms Related to Pain Management in Bone Tumors

BACKGROUND

Primary and metastatic bone tumor incidence has increased in the previous years. Pain is a common symptom and is one of the most important related factors to the decrease of quality of life in patients with bone tumor. Different pain management strategies are not completely effective and many patients afflicted by cancer pain cannot be controlled properly. In this sense, we need to elucidate the neurophysiology of cancer-induced pain, contemplating other components such as inflammation, neuropathies and cognitive components regarding bone tumors, and thus pave the way for novel therapeutic approaches in this field.

AIM

This study aims to identify the neurophysiology of the mechanisms related to pain management in bone tumors.

METHODS

Advanced searches were performed in scientific databases: PubMed, ProQuest, EBSCO, and the Science Citation index to get information about the neurophysiology mechanisms related to pain management in bone tumors.

RESULTS

The central and peripheral mechanisms that promote bone cancer pain are poorly understood. Studies have shown that bone cancer could be related to neurochemicals produced by tumor and inflammatory cells, coupled with peripheral sensitization due to nerve compression and injury caused by tumor growth. The activity of mesolimbic dopaminergic neurons, substance P, cysteine/ glutamate antiporter, and other neurochemical dynamics brings us putative strategies to suggest better and efficient treatments against pain in cancer patients.

CONCLUSION

Cancer-induced bone pain could include neuropathic and inflammatory pain, but with different modifications to the periphery tissue, nerves and neurochemical changes in different neurological levels. In this sense, we explore opportunity areas in pharmacological and nonpharmacological pain management, according to pain-involved mechanisms in this study.

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.

Expert Opinion: Exploring the Effectiveness and Tolerability of Capsaicin 179 mg Cutaneous Patch and Pregabalin in the Treatment of Peripheral Neuropathic Pain

Background and Objective

Treatment of peripheral neuropathic pain (PNP) remains a challenge. In the absence of clear predictors of response, clinical decision-making involves trial and error. While many classes of pharmacological agent are used and have shown efficacy, one of the most commonly used first-line treatments is pregabalin. However, in the 60% of PNP cases in which the pain is localized, a local treatment may be more suitable. This article will summarize the evidence for the relative effectiveness and tolerability of the capsaicin 179 mg patch and pregabalin in the treatment of PNP and highlight the expert opinion of the authors based on their own clinical experiences.

Results

When compared in a head-to-head trial in patients with PNP, capsaicin 179 mg patch provided non-inferior pain relief compared with an optimized dose of pregabalin, as well as a reduction in dynamic mechanical allodynia, faster onset of action, fewer systemic side effects, and greater treatment satisfaction. Adverse events associated with capsaicin patch are mainly application site reactions, compared with systemic and central nervous system effects with pregabalin. Studies indicate that capsaicin 179 mg patch is associated with a lower burden of therapy than pregabalin in terms of improved tolerability, lack of a daily pill burden, lack of drug-drug interactions, and increased regimen flexibility.

Conclusion

In localized neuropathic pain, evidence supports a pragmatic approach of using a local treatment before considering a systemic treatment. For treatment selection, the patient profile (eg, concomitant medication use, age) and the treatments' efficacy and tolerability profiles should be considered.

Capsaicin 8% dermal patch in clinical practice: an expert opinion

INTRODUCTION

Neuropathic pain (NP) is caused by a lesion or disease of the somatosensory system, which can severely impact patients' quality of life. The current-approved treatments for NP comprise of both centrally acting agents and topical drugs, including capsaicin 8% dermal patches, which is approved for the treatment of peripheral NP.

AREAS COVERED

The authors summarize literature data regarding capsaicin use in patients who suffer from NP and discuss the clinical applications of this topical approach.

EXPERT OPINION

Overall, the capsaicin 8% dermal patch is as effective in reducing pain intensity as other centrally active agents (i.e. pregabalin). Some studies have also reported fewer systemic side effects, a faster onset of action and superior treatment satisfaction compared with systemic agents. In our opinion, capsaicin 8% dermal patches also present additional advantages, such as a good systemic tolerability, the scarcity of adverse events, the possibility to combine it with other agents, and a good cost-effective profile. It is important to note that, as the mechanism of action of capsaicin 8% is the 'defunctionalization' of small afferent fibers through interaction with TRPV1 receptors, the peripheral expression of this receptor on nociceptor fibers, is crucial to predict patient's response to treatment.

Topical Treatment of Localized Neuropathic Pain in the Elderly

The prevalence of neuropathic pain in the older population has been reported to be very high and is most commonly localized to a circumscribed area. Treatment failure is frequent in neuropathic pain and is accompanied by central side effects with recommended oral drugs acting on the central nervous system. A number of topical pharmaceuticals are available on prescription and also sold over the counter. This review in persons aged older than 60 years shows the efficacy of lidocaine 5% and capsaicin 8% for localized neuropathic pain while results with other pharmaceuticals are rather inconsistent. Local application of drugs has a very limited systemic effect and the pharmacological advantages of local over systemic treatment are particularly interesting in older persons who often have comorbidities and take multiple medications. However, more information is needed on the efficacy and safety of lidocaine 5% and capsaicin 8% in older old persons and on the long-term effects of these pharmaceuticals. These studies should also pave the way for research and development in the field of topical analgesics with a satisfactory level of evidence-based medicine.

[Treatment of polyneuropathy: autonomic symptoms and pain]

BACKGROUND

The treatment of polyneuropathy includes symptomatic therapy of sensory, motor and autonomic dysfunctions.

AIM

This article provides an overview of the current treatment recommendations for polyneuropathy, focusing on pain.

METHODS

Current treatment guidelines will be discussed based on a literature research.

RESULTS

Calcium-channel anticonvulsants gabapentin/pregabalin as well as antidepressants duloxetine and amitriptyline are recommended as first line therapeutics. Alternatively, topical therapeutics can be used in the case of localized disorders. In individual cases, opioids or other antidepressants/anticonvulsants may be effective. Pharmacological treatment is often limited due to adverse events, which affect the central nervous system in particular.

DISCUSSION

In general, treatment for polyneuropathy should follow a multimodal concept and include the treatment of other symptoms. When choosing pain medication, comorbidities, patient's age and adverse events need to be taken into consideration. Phenotype-based stratification may support specialized pain therapy and achieve the best medical treatment.

Pain Management in Patients with Multiple Myeloma: An Update

Most patients with multiple myeloma (MM) suffer from chronic pain at every stage of the natural disease process. This review focuses on the most common causes of chronic pain in MM patients: (1) pain from myeloma bone disease (MBD); (2) chemotherapy-induced peripheral neuropathy as a possible consequence of proteasome inhibitor therapy (i.e., bortezomib-induced); (3) post-herpetic neuralgia as a possible complication of varicella zoster virus reactivation because of post-transplantation immunodepression; and (4) pain in cancer survivors, with increasing numbers due to the success of antiblastic treatments, which have significantly improved overall survival and quality of life. In this review, non-pain specialists will find an overview including a detailed description of physiopathological mechanisms underlying central sensitization and pain chronification in bone pain, the rationale for the correct use of analgesics and invasive techniques in different pain syndromes, and the most recent recommendations published on these topics. The ultimate target of this review was to underlie that different types of pain can be observed in MM patients, and highlight that only after an accurate pain assessment, clinical examination, and pain classification, can pain be safely and effectively addressed by selecting the right analgesic option for the right patient.

Effect of lidocaine cream analgesia for chest drain tube removal after video-assisted thoracoscopic surgery for lung cancer: a randomized clinical trial

BACKGROUND AND OBJECTIVES

Pain management makes an important contribution to good respiratory care and early recovery after thoracic surgery. Although the development of video-assisted thoracoscopic surgery (VATS) has led to improved patient outcomes, chest tube removal could be distressful experience for many patients. The aim of this trial was to test whether the addition of lidocaine cream would have a significant impact on the pain treatment during chest tube removal from patients who had undergone VATS for lung cancer.

METHODS

This clinical trial was a double-blind randomized study. Forty patients with histologically confirmed lung cancer amenable to lobectomy/segmentectomy were enrolled. All patients had standard perioperative care. Patients were randomly assigned to receive either epidural anesthesia plus placebo cream (placebo, Group P) or epidural anesthesia plus 7% lidocaine cream cutaneously around the chest tube insertion site and on the skin over the tube's course 20 min (Group L) before chest drain removal.

RESULTS

Visual analog scale (VAS) scores were higher in Group P (median 5, IQR, 3.25-8) than in Group L (median 2, IQR, 1-3). Pain intensities measured using a PainVision system were also higher in Group P (median 296.7, IQR, 216.9-563.5) than Group L (median 41.2, IQR, 11.8-97.0). VAS scores and the pain intensity associated with chest drain removal were significantly lower in Group L than Group P (p=0.0002 vs p<0.0001).

CONCLUSION

Analgesia using lidocaine cream is a very simple way to reduce the pain of chest tube removal after VATS.

TRIAL REGISTRATION NUMBER

UMIN000013824.

Management of neuropathic pain induced by surgery: Review of the literature by a group of experts specialized in pain management, anesthesia and surgery

Chronic postsurgical neuropathic pain (CPSNP) is frequent. While prevalence varies considerably according to type of operation and means of evaluation, it can reach 37% following breast surgery. Identification of risk factors related to the procedure and to the patient and taking into account the development of new, minimally invasive surgical techniques is increasingly nerve-sparing and reduces the likelihood of injury. CPSNP diagnosis in daily practice is facilitated by simple and quickly usable tools such as the NP4 4-question test. Management is based on pharmacological (analgesics, antiepileptics, antidepressants, local anesthetics) and non-pharmacological (kinesitherapy, neurostimulation, psychotherapy) approaches. In light of the present review of the literature, the authors, who constitute an expert group specialized in pain management, anesthesia and surgery, express their support for topical treatments (lidocaine, capsaicin) in treatment of localized postsurgical neuropathic pain in adults.

Perineural injection of botulinum toxin-A in painful peripheral nerve injury - a case series: pain relief, safety, sensory profile and sample size recommendation

Objectives: Subcutaneous injection of botulinum toxin-A (sBONT-A) is a novel treatment for peripheral neuropathic pain. While its analgesic effects are well documented, this treatment is often not comfortable and fails in patients who show signs of sensory loss but rarely allodynia. There are some case reports about perineural BONT-A injection (pBONT-A) which could be an alternative approach. Here we present a retrospective, open label case series of pBONT-A's efficacy and safety regarding neurological consequences involving changes in somatosensory profiles of both responders and non-responders. Methods: Sixty patients (53 ± 13years, 77% males) with PNI were treated with pBONT-A after a test injection with a local anesthetic, which prompted distinctive pain relief. Quantitative sensory testing (QST; DFNS protocol) and pain intensity were assessed before and ≥7 days post pBONT-A injection. Definition of response: satisfactory pain reduction of ≥30% NRS (numerical rating scale: 0 = no pain, 10 = worst pain) for ≥4 days. Statistics: Paired t-test, Mann-Whitney U-test, χ² test. Results: A temporary weak paresis in one case was clinically verified. The QST -parameters remained unchanged, but patients with more frequent hyperalgesia signs reported less analgesia (p = .04). The pBONT-A injection prompted pain relief by 24.8% (NRS: 6.0 ± 1.7 vs. 4.5 ± 2.1; p < .0001); 57% (n = 34) were responders (NRS: 6.0 ± 1.6 vs. 3.4 ± 1.6, relief of 43.4%; p < .0001). Based on these results, we suggest that future parallel design trials on pBONT-A need to include at least 84 patients. Discussion: Ultrasound-guided pBONT-A injection seems to be a safe treatment leading to a sufficient pain relief for some months without sensory changes. Surprisingly, pBONT-A showed a pronounced analgesic effect also in patients without signs of hyperalgesia.

[Drug management of cancer-related peripheral neuropathic pain: A systematic review of the literature]

The objective of the present systematic literature review was to provide an update on medical treatment of neuropathic pain in cancer patients. The number of cancer patients is steadily increasing. Pain is frequent in cancer patients. Few studies have focused on medical treatment of pain, and especially of neuropathic pain, in current or former cancer patients. The present systematic review of all studies published between December 2012 and August 2018 was intended to estimate the scale of this lack. In all, 27 articles were identified on a systematic PubMed search and from the authors' personal knowledge, confirming that scant data have been published. The heterogeneity of cancer patients, of cancer, and of pain go some way toward explaining this scarcity. Guidelines, founded mainly on results from non-cancer patients, recommend tricyclic antidepressants and antiepileptic drugs; local treatments have the advantage of good systemic tolerance. Larger-scale studies taking account of the etiology of neuropathic pain, its characteristics (strictly neuropathic or mixed) and patient characteristics (awaiting treatment, under treatment, recent or non-recent survivor, or in terminal phase) along the care pathway are needed to improve knowledge. The results of the present literature analysis can help future research.

Pain therapy for the elderly patient: is opioid-free an option?

PURPOSE OF REVIEW

Chronic noncancer pain is an increasing problem in elderly because of rising life expectancy together with an increase of potentially painful medical conditions. Concomitantly, adequate treatment of elderly is often limited by coexisting diseases and polypharmacy.This review summarizes the most important specifics presented by elderly patients and discusses the pharmacological and nonpharmacological options of pain management.

RECENT FINDINGS

A comprehensive pain assessment is a prerequisite for effective pain management. However, this can be a major challenge in patients who are unable to communicate adequately, that is, in patients with dementia. A recently developed electronic tool assessing automated facial expression and clinical behavioral indicators may help to solve this problem. The discussion about benefits and harms of opioids in elderly goes on. Although some authors underline the lack of efficacy together with the potential problems, such as, abuse, others report a beneficial effect in terms of pain relief, functional activities and disability. In addition, opioids have become an important treatment option in patients with restless legs syndrome. Various topical treatment options (i.e. capsaicin patch) and nonpharmacological interventions have been proven to be beneficial in elderly.

SUMMARY

Adequate pain management of elderly patients constitutes numerous pharmacological options including nonopioids, opioids, coanalgesics and topical agents. Due to age-related characteristics, all systemic analgesics have to be given very cautiously ('start low, go slow'). Whenever possible, treatment should be performed as a multimodal approach based on the biopsychosocial model of chronic pain.

Patients' Global Impression of Change in the management of peripheral neuropathic pain: Clinical relevance and correlations in daily practice

BACKGROUND

Patient-Reported Outcome (PRO) instruments have been developed to evaluate pain management in daily practice; the Patients' Global Impression of Change (PGIC) is particularly recommended by the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials. The prospective non-interventional multicenter PRO-QURE study aimed at assessing correlations between PGIC and pain measurements and treatment effects in patients followed in French pain centres.

METHODS

Respectively, 495 and 379 patients with peripheral neuropathic pain initiating treatment with capsaicin 8% cutaneous patch(es) (female, 62.6%; mean age, 54.0 ± 14.8 years; post-surgical or traumatic pain, 52.7%; mean pain duration, 42.2 ± 54.1 months; DN4 score >4, 92.9%) completed the PGIC and several other PRO instruments before (baseline) and 3 months (M3) after treatment application.

RESULTS

At M3, improvement ("much improved" or "very much improved") was observed in 23.0% of patients, associated with decreases of -3.0 ± 2.2, -2.5 ± 2.4, and -23.1 ± 19.7 in BPI pain intensity, BPI pain interference and NPSI total scores, respectively. The highest Spearman's rank correlation coefficients with PGIC were found for pain intensity (BPI: r = -0.479, p < 0.001), satisfaction with current state (Patient Acceptable Symptomatic State: r = 0.455, p < 0.001), and treatment effectiveness (TSQM: r = 0.431, p < 0.001); correlation coefficients were lower for all NPSI scores, BPI pain interference score, HAD scores and EQ-5D-3L index.

CONCLUSIONS

In daily clinical practice, significant improvement in peripheral neuropathic pain, as assessed by PGIC scores, significantly correlated with changes in well-established measures of pain intensity, pain interference with activities of daily living, mood and quality of life, confirming its clinical interest as PRO measure in real-world conditions.

SIGNIFICANCE

Clinically important improvement in peripheral neuropathic pain, as assessed by PGIC scores, significantly correlated with well-established measures of pain intensity, pain interference in daily life and treatment efficacy. This result, associated with the ease of administration and scoring, encourages the widespread use of the PGIC in daily practice.

Topical treatments for diabetic neuropathic pain

Diabetic neuropathic pain (DNP) has a huge impact on quality of life and can be difficult to treat. Oral treatment is the most frequently used method for DNP, but its use is often limited by systemic side effects. Topical use of drugs as an alternative option for DNP treatment is currently gaining interest. In the present review, a summary is provided of the available agents for topical use in patients with DNP, including lidocaine plasters or patches, capsaicin cream, gel or patches, amitriptyline cream, clonidine gel, ketamine cream, extracts from medicinal plants including nutmeg extracts and Citrullus colocynthis extract oil, and certain compounded topical analgesics. Furthermore, the potential efficacy of these treatments is addressed according to the available clinical research literature. It has been indicated that these topical drugs have the potential to be valuable additional options for the management of DNP, with adequate safety and continuous long-term treatment efficacy. Compounded topical agents are also effective and safe for patients with DNP and could be another area worthy of further investigation based on the strategy of using low-dose, complementary therapies for DNP. The findings indicate that developing topical drugs acting on different targets in the process of DNP is a valuable area of future research.

Assessing and Treating Chronic Pain in Patients with End-Stage Renal Disease

Pain is one of the most common symptoms among patients with end-stage renal disease (ESRD), and is often under recognized and not adequately managed in hemodialysis (HD) patients. Barriers to adequate pain management include poor awareness of the problem, insufficient medical education, fears of possible drug-related side effects, and common misconceptions about the inevitability of pain in elderly and HD patients. Caregivers working in HD should be aware of the possible consequences of inadequate pain assessment and management. Common pain syndromes in HD patients include musculoskeletal diseases and metabolic neuropathies, associated with typical intradialytic pain. Evaluating the etiology, nature, and intensity of pain is crucial for choosing the correct analgesic. A mechanism-based approach to pain management may result in a better outcome. Pharmacokinetic considerations on clearance alterations and possible toxicity in patients with ESRD should drive the right analgesic prescription. Comorbidities and polymedications may increase the risk of drug-drug interactions, therefore drug metabolism should be taken into account when selecting analgesic drugs. Automedication is common among HD patients but should be avoided to reduce the risk of hazardous drug administration. Further research is warranted to define the efficacy and safety of analgesic drugs and techniques in the context of patients with ESRD as generalizing information from studies conducted in the general population could be inappropriate and potentially dangerous. A multidisciplinary approach is recommended for the management of complex pain syndromes in frail patients, such as those suffering from ESRD.

Topical drug therapeutics for neuropathic pain

INTRODUCTION

Neuropathic pain (NP) is a particularly severe and intractable chronic condition that is not well treated by commonly recommended systemic pharmacological therapies, partly due to dose-limiting side effects or adverse events. The use of topical therapeutics for NP is growing and benefits from the reduced potential for adverse effects, as well as the ability to directly target peripheral pathological processes.

AREAS COVERED

The current review defines and describes the limitations of various commonly prescribed systemic pharmacological therapies for NP. It also provides a justification for increased research aimed at developing topical therapeutics for NP, particularly localized and peripheral NP. The review discusses the various classes of topical treatments used for NP, including agents that: block sensory inputs; activate inhibitory systems; provide mechanism-based therapeutics; are used in mucosal tissues; and include combinations that produce multimodal therapeutic effects.

EXPERT OPINION

There are arguments that the current topical therapeutics for NP rely too heavily on the use of local anesthetics and capsaicinoids, and more research is certainly needed on topical therapies that are multimodal and/or are targeted at the peripheral sources of pathology. The potential for novel topical therapeutics may be enhanced by further research on topical co-drugs, drug-drug salts, co-crystals and hydrates, and ionic liquids.

Clinical Manifestation of Acute, Subacute, and Chronic Low Back Pain in Different Age Groups: Low Back Pain in 35,446 Patients

BACKGROUND

Low back pain (LBP) is a major healthcare problem causing tremendous economic costs.

METHODS

Clinical manifestation of LBP was characterized in 35,446 patients. We focused on the comparison of the acute, subacute, and chronic LBP stage with regard to patients' ages, based on epidemiologic and clinical questionnaires (eg, painDETECT Questionnaire, Pain Disability Index), pain intensity, pain descriptors, and functional impairment.

RESULTS

We found that neuropathic components were most frequent in chronic LBP patients at the ages of 51 to 60 years. Elderly LBP patients showed a decrease in neuropathic and an increase in nociceptive pain. The most frequently reported pain descriptors were "pressure pain" and "pain attacks" through all stages of LBP, whereas "burning" and "prickling" were most frequent in the chronic stage. Patients after back surgery presented neuropathic pain symptoms most frequently and had the highest amount of pain medication intake.

CONCLUSIONS

Burning and prickling were revealed as possible indicators for LBP chronicity. Combined with pain attacks and pressure pain, these 4 pain descriptors might be a promising adjunct to pain intensity in terms of outcome parameters for future LBP studies. The decrease of neuropathic pain syndromes in the elderly might be explained by degenerative processes. The presented work provides important insights on LBP management in the acute, subacute, and chronic stages.

The Effect of a Combination of Diclofenac and Methadone Applied as Gel in a Human Experimental Pain Model - A Randomized, Placebo-controlled Trial

Pain involves responses in which both peripheral and central mechanisms contribute to the generation of pain. Pre-clinical laboratory data have supported that a topical formulation of combined diclofenac and methadone (Diclometh) may alleviate local pain, and potentially, the side effect profile should be low. We hypothesized that antiallodynic and antihyperalgesic effects of Diclometh could be demonstrated in a human experimental pain model and that Diclometh would be safe to administer. Thus, the aims were as follows: (i) to compare two doses of Diclometh versus placebo; and (ii) to assess the safety profile of Diclometh. The study was a crossover, randomized, double-blind, placebo-controlled comparison of two doses of Diclometh gel (0.1% and 0.2%) administered topically in healthy participants. Nerve growth factor (NGF) and capsaicin intradermal injections were used as human pain models. Pressure stimulation, contact heat stimulation, hyperalgesia (pinprick stimulation) and allodynia (brush stimulation) to mechanical stimulation were performed in the area where capsaicin and NGF were injected. Side effects were recorded on a four-point Likert scale. Twenty-one men completed the study (mean age 26.14 ± 5.3). Diclometh 0.2% reduced the capsaicin-induced dynamic mechanical allodynia compared to placebo (primary end-point, p = 0.03). No other primary or secondary end-points were found significantly different (all p > 0.05). All side effects were reported as mild with no differences between treatments (p = 0.15). Indication of antiallodynic effect of Diclometh 0.2% was found. Additionally, it was demonstrated that Diclometh was safe to use.

Transdermal and Topical Drug Administration in the Treatment of Pain

The comprehensive treatment of pain is multidimodal, with pharmacotherapy playing a key role. An effective therapy for pain depends on the intensity and type of pain, the patients' age, comorbidities, and appropriate choice of analgesic, its dose and route of administration. This review is aimed at presenting current knowledge on analgesics administered by transdermal and topical routes for physicians, nurses, pharmacists, and other health care professionals dealing with patients suffering from pain. Analgesics administered transdermally or topically act through different mechanisms. Opioids administered transdermally are absorbed into vessels located in subcutaneous tissue and, subsequently, are conveyed in the blood to opioid receptors localized in the central and peripheral nervous system. Non-steroidal anti-inflammatory drugs (NSAIDs) applied topically render analgesia mainly through a high concentration in the structures of the joint and a provision of local anti-inflammatory effects. Topically administered drugs such as lidocaine and capsaicin in patches, capsaicin in cream, EMLA cream, and creams containing antidepressants (i.e., doxepin, amitriptyline) act mainly locally in tissues through receptors and/or ion channels. Transdermal and topical routes offer some advantages over systemic analgesic administration. Analgesics administered topically have a much better profile for adverse effects as they relieve local pain with minimal systemic effects. The transdermal route apart from the above-mentioned advantages and provision of long period of analgesia may be more convenient, especially for patients who are unable to take drugs orally. Topically and transdermally administered opioids are characterised by a lower risk of addiction compared to oral and parenteral routes.