Novel insights on the management of pain: highlights from the ‘Science of Relief’ meeting

Tapentadol effects on brain response to pain in sensitized patients with knee osteoarthritis

OBJECTIVE

Pain sensitization, in the form of knee tenderness and anatomically spread hyperalgesia, is notably common in patients with knee osteoarthritis and is often refractory to conventional interventions. Tapentadol, as an opioid receptor agonist and noradrenaline reuptake inhibitor, has been proposed as a potentially effective symptomatic treatment for pain-sensitized osteoarthritis patients. We empirically tested whether tapentadol could attenuate brain response to painful stimulation on the tender knee using functional MRI.

METHODS

Pressure painful stimulation was applied to the articular interline and the tibial surface, a commonly sensitized site surrounding the joint. Thirty patients completed the crossover trial designed to compare prolonged release tapentadol and placebo effects administered over 14 days.

RESULTS

We found no effects in the direction of the prediction. Instead, patients administered with tapentadol showed stronger activation in response to pressure on the tender site in the right prefrontal cortex and somatosensory cortices. The somatosensory effect was compatible with the spread of neural activation around the knee cortical representation. Consistent with the functional MRI findings, the patients showed higher clinical ratings of pain sensitization under tapentadol and a significant positive association was identified between the number of tapentadol tablets and the evoked subjective pain.

CONCLUSION

The tapentadol effect paradoxically involved both the spread of the somatosensory cortex response and a stronger activation in prefrontal areas with a recognized role in the appraisal of pain sensations. Further studies are warranted to explore how osteoarthritis patients may benefit from powerful analgesic drugs without the associated risks of prolonged use. EudraCT-[2016-005082-31].

Capsaicin 8% Patch Treatment in Non-Freezing Cold Injury: Evidence for Pain Relief and Nerve Regeneration

Introduction: Neuropathic pain associated with Non-freezing Cold Injury (NFCI) is a major burden to military service personnel. A key feature of NFCI is reduction of the intra-epidermal nerve fibre density in skin biopsies, in keeping with painful neuropathy. Current oral treatments are generally ineffective and have undesirable side effects. Capsaicin 8% patch (Qutenza) has been shown to be well-tolerated and effective for reducing neuropathic pain, for up to 3 months after a single 30-minute application.

Methods: In this single-centre open label study, 16 military participants with NFCI (mean duration 49 months) received 30-minute Capsaicin 8% patch treatment to the feet and distal calf. Pain symptoms were assessed using a pain diary (with the 11-point Numerical Pain Rating Scale, NPRS) and questionnaires, the investigations included skin biopsies, performed before and three months after treatment.

Results: Participants showed significant decrease in spontaneous pain (mean NPRS: −1.1, 95% CI: 0.37 to 1.90; p = 0.006), and cold-evoked pain (−1.2, 95% CI: 0.40 to 2.04; p = 0.006). The time-course of pain relief over 3 months was similar to other painful neuropathies. Patient Global Impression of Change showed improvement (p = 0.0001).

Skin punch biopsies performed 3 months after the patch application showed significant increase of nerve fibres with structural marker PGP9.5 (intra-epidermal nerve fibres [IENFs], p < 0.0001; sub-epidermal nerve fibres [SENFs]; p =< 0.0001), and of regenerating nerve fibres with their selective marker GAP43 (p = 0.0001). The increase of IENFs correlated with reduction of spontaneous (p = 0.027) and cold-evoked pain (p = 0.019).

Conclusions: Capsaicin 8% patch provides an exciting new prospect for treatment of NFCI, with regeneration and restoration of nerve fibres, for the first time, in addition to pain relief.

Capsaicin 179-mg cutaneous patch in the treatment of post-surgical neuropathic pain: a scoping review of current evidence and place in therapy

INTRODUCTION

The use of topical agents has been suggested for post-surgical neuropathic pain. A high-concentration capsaicin 179-mg cutaneous patch (Qutenza™) is licensed in adults for chronic neuropathic pain in the EU, and neuropathic pain with post-herpetic neuralgia and neuropathic pain with diabetic peripheral neuropathy in the USA. This article aims to describe the use of a topical capsaicin 179-mg cutaneous patch in the treatment of PSNP.

AREA COVERED

This narrative review presents the relevant clinical aspects of the use of a topical capsaicin 179-mg cutaneous patch for the treatment of post-surgical neuropathic pain (PSNP). Randomized control trials, observational studies, case series, and reports investigating the clinical use of the capsaicin patch were searched through MEDLINE, EMBASE, AMED, Cochrane Library, CINAHL, Web of Science, and ROAD databases. Trials from citation lists of reviewed articles and hand-searching were added. The search concluded in September 2020. 10/20 articles were considered.

EXPERT OPINION

Some clinical studies demonstrated the efficacy of the capsaicin 179-mg patch in PSNP as monotherapy and concomitant treatment with oral treatments. This topical treatment of PSNP is better tolerated and accepted compared with systemic treatments. To maximize the effectiveness of the treatment, correct administration recommendations should be followed.

Capsaicin 8% patch Qutenza and other current treatments for neuropathic pain in chemotherapy-induced peripheral neuropathy (CIPN)

PURPOSE OF REVIEW

Current oral treatments for neuropathic pain associated with chemotherapy-induced peripheral neuropathy (CIPN) have limited clinical efficacy, and undesirable side-effects. Topically delivered treatments have the advantage of avoiding CNS side-effects, while relieving pain. We have reviewed treatments of neuropathic pain associated with CIPN, focusing on the Capsaicin 8% patch, which can provide pain relief for up to 3 months or longer after a single 30-60-min application.

RECENT FINDINGS

Capsaicin 8% patch is a licensed treatment in the EU/UK for neuropathic pain and shown to be safe and effective in providing pain relief for patients with CIPN. Repeated daily oral or topical administrations are not required, as with other current treatments. The side-effects are transient and restricted to the time around patch application. New evidence suggests the Capsaicin 8% patch can promote the regeneration and restoration of skin nerve fibres in CIPN, in addition to the pain relief.

SUMMARY

The Capsaicin 8% patch is now often a preferred a treatment option for localised neuropathic pain conditions, including the feet and hands in patients with CIPN. Capsaicin 8% patch can be repeated three-monthly, if needed, for a year. In addition to pain relief, it may have a disease-modifying effect.

Effect of an Online Reimbursement Application System on Prescribing of Lidocaine 5% Medicated Plaster in the Republic of Ireland

BACKGROUND

The lidocaine 5% medicated plaster, Versatis^®, has one therapeutic indication listed on the Summary of Product Characteristics-symptomatic relief of post-herpetic neuralgia (PHN) in adults. Increased expenditure on Versatis^® suggests that there is considerable off-label use. To support the appropriate use of Versatis^®, the Health Service Executive's Primary Care Reimbursement Service (PCRS) introduced a reimbursement application system for Versatis^® from 1 September 2017.

OBJECTIVE

The aim of this study was to investigate the effect of introducing a reimbursement application system on Versatis^® prescribing under the General Medical Services (GMS) scheme.

METHODS

This study was carried out using prescription dispensing data from the PCRS pharmacy claims database. We carried out segmented linear regression to assess changes in the Versatis^® prescribing rate per 1000 GMS eligible population, before and after the introduction of the online reimbursement application system.

RESULTS

The results of the segmented regression analysis show that there was a statistically significant level (- 4.91, p < 0.001) and trend change (- 0.69, p < 0.001) in the rate of Versatis^® prescribing post-introduction of the reimbursement application system. In the year prior to the introduction of the system, 2016, the annual GMS expenditure on Versatis^® lidocaine 5% patches was over €27 million, whereas the GMS expenditure in 2018 was reduced to just over €2 million.

CONCLUSION

In our study, a substantial decrease in the dispensing of Versatis^® was seen after the implementation of a reimbursement application system. Prescribing of Versatis^® should be restricted to patients with a diagnosis of PHN not only to reduce costs, but to ensure evidence-based use of this medication.

Modulation of sensitization processes in the management of pain and the importance of descending pathways: a role for tapentadol?

Objective: This paper presents and discusses recent evidence on the pathophysiological mechanisms of pain. The role of tapentadol - an opioid characterized by an innovative mechanism of action (i.e. µ-opioid receptor [MOR] agonism and inhibition of noradrenaline [NA] reuptake [NRI]) - in the modulation of pain, and the most recent pharmacological evidence on this molecule (e.g. the µ-load concept) are also presented and commented upon.Methods: Narrative review.Results: Solid evidence has highlighted the importance of central sensitization in the transition from acute to chronic pain. In particular, the noradrenergic system holds a major role in limiting central sensitization and the progression to chronic pain. Therefore, pharmacological modulation of the noradrenergic system appears to be a well-grounded strategy for the control of chronic pain. Tapentadol is characterized by a to-date-unique mechanism of action, since it acts both as a MOR agonist and as an inhibitor of NA reuptake. The synergistic interaction of these two mechanisms allows a strong analgesic effect by acting on both ascending and descending pathways. Of note, the reduced µ-load of tapentadol limits the risk of opioid-related adverse events, such as gastrointestinal disturbances. Moreover, the NA component becomes predominant, at least, in some types of pain, with consequent specific clinical efficacy in the treatment of neuropathic and chronic pain.Conclusions: According to these characteristics, tapentadol appears suitable in the treatment of severe uncontrolled chronic pain characterized by both a nociceptive and a neuropathic component, such as osteoarthritis or back pain.

Modulation of sensitization processes in the management of pain and the importance of descending pathways: a role for tapentadol?

Objective: This paper presents and discusses recent evidence on the pathophysiological mechanisms of pain. The role of tapentadol - an analgesic molecule characterized by an innovative mechanism of action (i.e. µ-opioid receptor [MOR] agonism and inhibition of noradrenaline [NA] reuptake [NRI]) - in the modulation of pain, and the most recent pharmacological evidence on this molecule (e.g. the µ-load concept) are also presented and commented upon.Methods: Narrative review.Results: Solid evidence has highlighted the importance of central sensitization in the transition from acute to chronic pain. In particular, the noradrenergic system holds a major role in limiting central sensitization and the progression to chronic pain. Therefore, pharmacological modulation of the noradrenergic system appears to be a well-grounded strategy for the control of chronic pain. Tapentadol is characterized by a to-date-unique mechanism of action since it acts both as a MOR agonist and as an inhibitor of NA reuptake. The synergistic interaction of these two mechanisms allows a strong analgesic effect by acting on both ascending and descending pathways. Of note, the reduced µ-load of tapentadol has two important consequences: first, it limits the risk of opioid-related adverse events, as well as the risk of dependence; second, the NA component becomes predominant at least in some types of pain with consequent specific clinical efficacy in the treatment of neuropathic and chronic pain.Conclusions: According to these characteristics, tapentadol appears suitable in the treatment of chronic pain conditions characterized by both a nociceptive and a neuropathic component, such as osteoarthritis or back pain.