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

The PATCH trial: efficacy and safety of 5% lidocaine-medicated plaster for the treatment of patients with trigeminal neuralgia: a study protocol for a multicentric, double-blind, enriched enrolment randomised withdrawal, vehicle-controlled study

INTRODUCTION

Trigeminal neuralgia (TN) is characterised by a sudden, severe, electric shock like paroxysmal pain, which is almost always associated with triggers. Carbamazepine is the first-line medical management of TN. However, side effects are common. Currently, there is no ideal treatment for TN. Since there is a known abnormality of Na+ channels in the trigger zone, 5% lidocaine-medicated plaster (LMP), which can block the Na+ channels on Aδ and C fibres, is an effective treatment method in many chronic pain conditions. A case report has found the benefit of LMP for the treatment of TN without any side effects. Whether LMP is an option for the treatment of TN is worth exploring.

METHODS AND ANALYSIS

The PATCH trial is a double-blind, enriched enrolment with randomised withdrawal, vehicle-controlled trial, aiming to explore the effects and safety of LMP in patients with TN. There is a 3-week initial open-label phase, followed by a 4-week double-blind treatment phase for responders. In the double-blind phase, patients will have to withdraw from this PATCH study if they meet one of the following criteria for treatment failure such as: >50% increase in pain intensity or paroxysms, lack of efficacy or side effects. The primary outcome will be the number of treatment failures. Adverse events will also be monitored throughout the study.

ETHICS AND DISSEMINATION

This study protocol has been approved by the Institutional Review Board of Beijing Tiantan Hospital (approval number: KY 2020-102-02). The results will be disseminated in international academic meetings and published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04570293.

Localized neuropathic pain: an expert consensus on local treatments

BACKGROUND

Pain localization is one of the hallmarks for the choice of first-line treatment in neuropathic pain. This literature review has been conducted to provide an overview of the current knowledge regarding the etiology and pathophysiology of localized neuropathic pain (LNP), its assessment and the existing topical pharmacological treatments.

MATERIALS AND METHODS

Literature review was performed using Medline from 2010 to December 2016, and all studies involving LNP and treatments were examined. A multidisciplinary expert panel of five pain specialists in this article reports a consensus on topical approaches that may be recommended to alleviate LNP and on their advantages in clinical practice.

RESULTS

Successive international recommendations have included topical 5% lidocaine and 8% capsaicin for LNP treatment. The expert panel considers that these compounds can be a first-line treatment for LNP, especially in elderly patients and patients with comorbidities and polypharmacy. Regulatory LNP indications should cover the whole range of LNP and not be restricted to specific etiologies or sites. Precautions for the use of plasters must be followed cautiously.

CONCLUSION

Although there is a real need for more randomized controlled trials for both drugs, publications clearly demonstrate excellent risk/benefit ratios, safety, tolerance and continued efficacy throughout long-term treatment. A major advantage of both plasters is that they have proven efficacy and may reduce the risk of adverse events such as cognitive impairment, confusion, somnolence, dizziness and constipation that are often associated with systemic neuropathic pain treatment and reduce the quality of life. Topical modalities also may be used in combination with other drugs and analgesics with limited drug-drug interactions.

The effects of chemical and physical penetration enhancers on the percutaneous permeation of lidocaine through equine skin

Background

The effect of physical and chemical permeation enhancers on in vitro transdermal permeation of lidocaine was investigated in the horse.

Therefore, the effect of six vehicles (phosphate-buffered saline (PBS), 50% ethanol, 50% propylene glycol, 50% isopropylalcohol, 50% isopropylalcohol/isopropylmyristate and 50% dimethylsulfoxide) was examined as well as the effect of microneedle pretreatment with different needle lengths on transdermal drug delivery of lidocaine.

The skin was obtained from the thorax of six Warmblood horses and was stored up to two weeks at - 20°C. Franz-type diffusion cells were used to study the transdermal permeation through split skin (600 μm thickness). The amount of lidocaine in the receptor fluid was determined by UV–VIS high-performance liquid chromatography.

Results

All investigated vehicle supplementations diminished the transdermal flux of lidocaine through equine skin in comparison to pure PBS except dimethylsulfoxide, which resulted in comparable permeation rates to PBS. The maximum flux (J_max) was 1.6-1.8 fold lower for lidocaine applied in 50% ethanol, propylene glycol, isopropylalcohol and isopropylalcohol/isopropylmyristate. A significant higher J_max of lidocaine was observed when lidocaine was applied in PBS onto microneedle pretreated skin with similar permeation rates in both needle lengths. After 6 hours, 1.7 fold higher recovery rates were observed in the microneedle pretreated skin samples than in the untreated control samples. The lagtimes were reduced to 20–50% in the microneedle pretreated skin samples.

Conclusion

Microneedles represent a promising tool for transdermal lidocaine application in the horse with a rapid systemic bioavailability.

Update on neuropathic pain treatment: ion channel blockers and gabapentinoids

Neuropathic pain is a debilitating chronic pain condition, which remains difficult to treat. The current mainstays of treatment include physical therapy, interventional procedures and medications. Among medications, ion channel blockers and gabapentinoids are the 2 classes of drugs commonly used to treat neuropathic pain. It has been suggested that these medications may be useful to treat a variety of neuropathic pain conditions. This article provides several updates on the utility of both ion channel blockers and gabapentinoids for the treatment of neuropathic pain.

Topical pain management with the 5% lidocaine medicated plaster--a review

BACKGROUND

The topical 5% lidocaine medicated plaster is recommended as first-line treatment for localized peripheral neuropathic pain.

SCOPE

In order to provide an overview of the efficacy and safety of the lidocaine plaster in the treatment of different neuropathic pain conditions, all efficacy and safety studies (randomized, controlled, or open-label with well described methodology), case reports, and pharmacological studies on the lidocaine plaster retrieved from a PubMed literature research (1960-March 2012) plus additional references identified from retrieved articles were included.

FINDINGS

The lidocaine plaster is efficacious in the treatment of neuropathic pain symptoms associated with previous herpes zoster infection. Results from a large open-label controlled study suggest that the lidocaine plaster could be at least as effective as systemic pregabalin in the treatment of postherpetic neuralgia and painful diabetic polyneuropathy. Open-label studies indicate efficacy in the treatment of other localized neuropathic pain conditions, such as painful idiopathic sensory polyneuropathy, complex regional pain syndrome, carpal tunnel syndrome sequelae, postsurgical and posttraumatic pain. Quality of life markedly improved in a variety of neuropathic pain conditions and long-term treatment provided sustained relief in patients with neuropathic pain who are responsive to lidocaine plaster. The lidocaine plaster is usually well tolerated. The risk of systemic adverse events and pharmacokinetic interactions with concomitant medication is minimal owing to low systemic exposure.

CONCLUSIONS

Treatment of several, primarily neuropathic and mixed-pain conditions with the 5% lidocaine medicated plaster was found efficacious and safe. Further controlled studies, in particular where only small open-label studies or case reports are available, should be considered.

Efficacy of piroxicam patch compared to lidocaine patch for the treatment of postherpetic neuralgia

BACKGROUND

The lidocaine patch has been effectively used as a first-line therapy to treat neuropathic pain such as postherpetic neuralgia (PHN).

OBJECTIVE

To evaluate the safety and efficacy of the topical piroxicam patch as a treatment option for the treatment of PHN.

METHODS

Eighteen patients completed a 3-session study, applying three different patches (lidocaine, piroxicam and control) in random order. A maximum of three patches were applied to the most painful area for three consecutive days (12 hours on followed by 12 hours off). Each session was conducted at least seven days apart. The changes in visual analog scale (VAS) scores based pain intensity, quality of sleep and adverse effects were recorded.

RESULTS

When compared to the control, both the lidocaine and piroxicam patches significantly reduced the mean VAS scores of pain intensity of all different types. However, the lidocaine patch was better at reducing allodynia, whereas the piroxicam patch was more effective for dull pain. The lidocaine patch worked faster than the piroxicam patch for the response to overall pain relief.

CONCLUSION

The results of this study suggest the use of the piroxicam patch for dull pain and in patients where the lidocaine patch is contraindicated.

[Lidocaine patch for therapy of neuropathic and non-neuropathic pain. A clinical case series of 87 patients]

BACKGROUND

Topical lidocaine patches (LP) reduce pain in postherpetic neuralgia and other forms of focal neuropathy. The aim of this study was to determine clinical predictors of therapeutic success.

MATERIAL AND METHODS

The medical histories of 87 patients with neuropathic (NS) and non-neuropathic pain (NNS) who had received LP as an add-on to their established pain medication were retrospectively analyzed. The variables assessed were gender, age, analgesic co-medication, pain localization, adverse effects and presence of dynamic allodynia. The impact of these variables on the clinical pain-relieving effect (scored on a 5-point scale) was investigated.

RESULTS

A total of 24 out of 28 patients with manifest allodynia scored the therapy with LP as beneficial, patients without allodynia (n=59, 67.8%) profited significantly less frequently with only 39% (p<0.001). The probability of profiting from LP therapy in the presence of allodynia was found to be about tenfold higher compared to patients without allodynia (odds ratio 9.14). Of the 87 patients investigated 48 were female (55.2%). Allodynia was considerably more frequent in women (39.6%) compared to men (23.1%) but this was insignificant. Of the female patients 62.5% responded to LP treatment, compared to only 43.6% of men. In more than 60% of cases rated as very good pain relief allodynia was manifest and in non-responders only in less than 10%. The variables age, pain localization and analgesic co-medication were not related with the success of therapy.

DISCUSSION

Patients with manifest allodynia profited significantly more frequently from LP therapy and were less frequently non-responders. Female patients showed therapeutic success more often together with a higher rate of allodynia.

CONCLUSIONS

In the presence of allodynia, in especially of neuropathic origin, LP seems to be an effective and save option for add-on therapy, this being independent from pain localization and age. Gender specific effects however need more systematic investigation.

Pharmacologic management of neuropathic pain: evidence-based recommendations

Patients with neuropathic pain (NP) are challenging to manage and evidence-based clinical recommendations for pharmacologic management are needed. Systematic literature reviews, randomized clinical trials, and existing guidelines were evaluated at a consensus meeting. Medications were considered for recommendation if their efficacy was supported by at least one methodologically-sound, randomized clinical trial (RCT) demonstrating superiority to placebo or a relevant comparison treatment. Recommendations were based on the amount and consistency of evidence, degree of efficacy, safety, and clinical experience of the authors. Available RCTs typically evaluated chronic NP of moderate to severe intensity. Recommended first-line treatments include certain antidepressants (i.e., tricyclic antidepressants and dual reuptake inhibitors of both serotonin and norepinephrine), calcium channel alpha2-delta ligands (i.e., gabapentin and pregabalin), and topical lidocaine. Opioid analgesics and tramadol are recommended as generally second-line treatments that can be considered for first-line use in select clinical circumstances. Other medications that would generally be used as third-line treatments but that could also be used as second-line treatments in some circumstances include certain antiepileptic and antidepressant medications, mexiletine, N-methyl-D-aspartate receptor antagonists, and topical capsaicin. Medication selection should be individualized, considering side effects, potential beneficial or deleterious effects on comorbidities, and whether prompt onset of pain relief is necessary. To date, no medications have demonstrated efficacy in lumbosacral radiculopathy, which is probably the most common type of NP. Long-term studies, head-to-head comparisons between medications, studies involving combinations of medications, and RCTs examining treatment of central NP are lacking and should be a priority for future research.