Treatment of postherpetic neuralgia: a review of therapeutic options

Efficacy of Gasserian Ganglion High-Voltage, Long-Duration Pulsed Radiofrequency Combined With Block on Acute/Subacute Zoster-Related Trigeminal Neuralgia

Background: Trigeminal postherpetic neuralgia (TPHN) is a severe chronic pain that can lead to various socioeconomic consequences. Therefore, it is necessary to explore optimal treatment options for acute/subacute herpes zoster (HZ)-related trigeminal neuralgia and prevent the further development of TPHN. High-voltage, long-duration pulsed radiofrequency (HL-PRF) of the Gasserian ganglion is a new surgical intervention used to treat PHN. A ganglion block has been reported to possess anti-inflammatory effects and potential analgesic benefits. Methods: We included 83 patients with HZ-related acute/subacute trigeminal neuralgia admitted from January 1, 2021, to June 1, 2023, and received Gasserian ganglion HL-PRF combined with block. A 6-month follow-up was conducted, including Numerical Rating Scale (NRS) scores, Pittsburgh Sleep Quality Index (PSQI), the incidence of TPHN, the dosage of anticonvulsants and analgesics, efficacy, and adverse events. Results: All patients showed a significant decrease in postoperative NRS scores (p < 0.05). The NRS scores of the acute HZ group were consistently lower than those of the subacute HZ group at different time points (p < 0.01). The overall incidence of TPHN from the onset of HZ to 12 weeks is 21.68%. The incidence of TPHN in the acute phase group was 12.77%, significantly lower than the 33.33% in the subacute phase group (p=0.024). The effective rate was 74.7% in all patients, at 3 months after the treatment. The effective rate was 82.98% in the acute phase group and 63.89% in the subacute phase group, showing a statistically significant difference (p=0.047). The PSQI score of the acute group was consistently lower than that of the subacute group (p < 0.01). The dosage of analgesics and anticonvulsants used in the acute HZ group was lower than that in the subacute group (p < 0.01). All patients did not experience serious adverse reactions. Conclusions: Gasserian ganglion HL-PRF combined with block can be an effective and safe technique to relieve the pain of acute/subacute zoster-related trigeminal neuralgia and prevent the incidence of TPHN.

Causal effect of lifestyle and metabolic indicator with herpes zoster: a two-sample Mendelian randomization study

Background

Previous observational studies have reported certain causal relationships between factors such as smoking, alcohol consumption, obesity, physical activity, metabolic disorders, and the incidence of herpes zoster (HZ). However, there is controversy regarding the observed results across different studies. Our objective was to investigate the causal effects of these risk factors on the risk of herpes zoster through a Mendelian randomization analysis using two-sample bidirectional approaches.

Methods

We conducted two-sample bidirectional Mendelian randomization analyses to explore the causal relationships between different lifestyles, obesity assessment indices, metabolic indicators, and the risk of herpes zoster. All exposure and outcome data were sourced from publicly available data from genome-wide association studies.

Results

In the inverse-variance weighted (IVW) analysis, body mass index (BMI) (OR: 1.160, 95% CI: 1.030-1.307, p = 0.014), Body fat percentage (BFP) (OR: 1.241, 95% CI: 1.050-1.467, p = 0.011), and whole body fat mass (WBFM) (OR: 1.199, 95% CI: 1.057-1.362, p = 0.005) exhibited positive associations with the risk of HZ. However, usual walking pace (UWP) (OR: 0.498, 95% CI: 0.254-0.976, p = 0.042) demonstrated a significant negative correlation with HZ risk. Other factors including alcohol intake frequency, smoking initiation, smoking status, insomnia, and sleep duration did not show significant causal relationships with HZ.

Conclusion

Mendelian randomization studies revealed that BMI, BFP, and WBFM are risk factors for HZ. UWP showed a protective effect against HZ. These findings provide a straightforward method for evaluating future clinical practices aiming to develop personalized management strategies and assess high-risk populations for HZ.

Turning the Tide against Herpes Zoster in Rheumatoid Arthritis Patients Treated with JAK Inhibitors

Objectives: This study aimed to evaluate the incidence of Herpes Zoster (HZ) in patients with rheumatoid arthritis (RA) treated with Janus kinase inhibitors (JAKi), and to predict potential risk factors for HZ development. Methods: We retrospectively analysed medical records from RA patients at our rheumatology unit who met the 2010 ACR/EULAR criteria for RA and were receiving JAKi. The incidence and course of HZ were assessed through chart review and supplementary phone interviews. Results: A total of 198 JAKi-treated patients were monitored for an average of 18.5 months. Nine subjects experienced HZ, resulting in an incidence of 2.95 per 100 patient-years. No demographic or treatment-related differences were found among patients who developed HZ and those who did not. Disease duration (OR: 1.06, 95% CI: 1.01-1.12), time on JAKi treatment (OR: 1.04, 95% CI: 1.009-1.073), higher disease activity at JAKi initiation (OR: 4.16, 95% CI: 1.07-16.17), and at 3-month follow-up (OR: 6.0, 95% CI: 1.35-26.60) were identified as predictors of HZ occurrence. Thirty-six patients received vaccination against HZ, and none reported adverse reactions or flare-ups during a mean follow-up of 9.6 months. Conclusions: The incidence of HZ aligns with published data, suggesting that disease and treatment duration, as well as disease activity, are significant predictors of HZ in RA patients on JAKi therapy. Vaccination against HZ proved to be safe and effective, underscoring its potential protective value in this patient population.

The efficacy of repetitive transcranial magnetic stimulation in postherpetic neuralgia: a meta-analysis of randomized controlled trials

Purpose

This systematic review and meta-analysis aimed to evaluate the efficacy of repetitive transcranial magnetic stimulation (rTMS) in postherpetic neuralgia (PHN).

Methods

Through an extensive search in four databases until October 2023, we selected five randomized controlled trials adhering to our specific criteria, involving 257 patients in total. For continuous outcomes, the standardized mean difference (SMD) was calculated. Heterogeneity among the studies was assessed using Cochran's I 2 and Q statistics, adopting a random-effects model for I 2 values over 50%. For assessing potential publication bias, we utilized both funnel plot and Egger's test.

Results

Our analysis found that rTMS reduced the overall visual analogue scale (VAS) (SMD: -1.52, 95% CI: -2.81 to -0.23, p = 0.02), VAS at 1 month post-treatment (SMD: -2.21, 95% CI: -4.31 to -0.10, p = 0.04), VAS at 3 months post-treatment (SMD: -1.51, 95% CI: -2.81 to -0.22, p = 0.02), as well as patients' global impression of change scale (PGIC) (SMD: -1.48, 95% CI: -2.87 to -0.09, p = 0.04) and short-form McGill pain questionnaire (SF-MPQ) (SMD: -1.25, 95% CI: -2.41 to -0.09, p = 0.03) compared to the sham-rTMS group.

Conclusion

Our study suggests that rTMS might have a potential alleviating effect on PHN symptoms. However, due to the limited number of studies and variations in rTMS parameters, larger sample studies involving more diverse populations, as well as further clarification of the most appropriate stimulation protocol, are still needed.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, Identifier ID: CRD42023488420.

Gabapentin alleviated the cough hypersensitivity and neurogenic inflammation in a guinea pig model with repeated intra-esophageal acid perfusion

OBJECTIVE

The anti-tussive effect of gabapentin and its underlying neuromodulatory mechanism were investigated via a modified guinea pig model of gastroesophageal reflux-related cough (GERC).

METHODS

Intra-esophageal perfusion with hydrochloric acid (HCl) was performed every other day 12 times to establish the GERC model. High-dose gabapentin (48 mg/kg), low-dose gabapentin (8 mg/kg), or saline was orally administered for 2 weeks after modeling. Cough sensitivity, airway inflammation, lung and esophagus histology, levels of substance P (SP), and neurokinin-1 (NK1)-receptors were monitored.

RESULTS

Repeated intra-esophageal acid perfusion aggravated the cough sensitivity in guinea pigs in a time-dependent manner. The number of cough events was significantly increased after 12 times HCl perfusion, and the hypersensitivity period was maintained for 2 weeks. The SP levels in BALF, trachea, lung, distal esophagus, and vagal ganglia were increased in guinea pigs receiving HCl perfusion. The intensity of cough hypersensitivity in the GERC model was significantly correlated with increased SP expression in the airways. Both high and low doses of gabapentin administration could reduce cough hypersensitivity exposed to HCl perfusion, attenuate airway inflammatory damage, and inhibit neurogenic inflammation by reducing SP expression from the airway and vagal ganglia.

CONCLUSIONS

Gabapentin can desensitize the cough sensitivity in the GERC model of guinea pig. The anti-tussive effect is associated with the alleviated peripheral neurogenic inflammation as reflected in the decreased level of SP.

HSV-1 infection-induced herpetic neuralgia involves a CCL5/CCR5-mediated inflammation mechanism

Herpetic-related neuralgia (HN) caused by varicella-zoster virus (VZV) infection is one of the most typical and common neuropathic pain in the clinic. However, the potential mechanisms and therapeutic approaches for the prevention and treatment of HN are still unclear. This study aims to provide a comprehensive understanding of the molecular mechanisms and potential therapeutic targets of HN. We used an HSV-1 infection-induced HN mouse model and screened the differentially expressed genes (DEGs) in the DRG and spinal cord using an RNAseq technique. Moreover, bioinformatics methods were used to figure out the signaling pathways and expression regulation patterns of the DEGs enriched. In addition, quantitative real-time RT-PCR and western blot were carried out to further confirm the expression of DEGs. HSV-1 inoculation in mice resulted in mechanical allodynia, thermal hyperalgesia, and cold allodynia, following the infection of HSV-1 in both DRG and spinal cord. Besides, HSV-1 inoculation induced an up-regulation of ATF3, CGRP, and GAL in DRG and activation of astrocytes and microglia in the spinal cord. Moreover, 639 genes were upregulated, 249 genes were downregulated in DRG, whereas 534 genes were upregulated and 12 genes were downregulated in the spinal cord of mice 7 days after HSV-1 inoculation. GO and KEGG enrichment analysis suggested that immune responses and cytokine-cytokine receptor interaction are involved in DRG and spinal cord neurons in mice after HSV-1 infection. In addition, CCL5 and its receptor CCR5 were significantly upregulated in DRG and spinal cord upon HSV-1 infection in mice. And blockade of CCR5 exhibited a significant analgesic effect and suppressed the upregulation of inflammatory cytokines in DRG and spinal cord induced by HSV-1 infection in mice. HSV-1 infection-induced allodynia and hyperalgesia in mice through dysregulation of immune response and cytokine-cytokine receptor interaction mechanism. Blockade of CCR5 alleviated allodynia and hyperalgesia probably through the suppression of inflammatory cytokines. Therefore, CCR5 could be a therapeutic target for the alleviation of HSV-1 infection-induced HN.

Rodent models of postherpetic neuralgia: How far have we reached?

Background

Induced by varicella zoster virus (VZV), postherpetic neuralgia (PHN) is one of the common complications of herpes zoster (HZ) with refractory pain. Animal models play pivotal roles in disclosing the pain mechanisms and developing effective treatments. However, only a few rodent models focus on the VZV-associated pain and PHN.

Objective

To summarize the establishment and characteristics of popular PHN rodent models, thus offer bases for the selection and improvement of PHN models.

Design

In this review, we retrospect two promising PHN rodent models, VZV-induced PHN model and HSV1-induced PHN model in terms of pain-related evaluations, their contributions to PHN pathogenesis and pharmacology.

Results

Significant difference of two PHN models is the probability of virus proliferation; 2) Most commonly used pain evaluation of PHN model is mechanical allodynia, but pain-induced anxiety and other behaviours are worth noting; 3) From current PHN models, pain mechanisms involve changes in virus gene and host gene expression, neuroimmune-glia interactions and ion channels; 4) antiviral drugs and classical analgesics serve more on the acute stage of herpetic pain.

Conclusions

Different PHN models assessed by various pain evaluations combine to fulfil more comprehensive understanding of PHN.

Efficacy and Safety of Pulsed Radiofrequency in Herpes Zoster Related Trigeminal Neuralgia: A Systematic Review and Meta-Analysis

Purpose

Pulsed radiofrequency (PRF) is a neuromodulation technique for neuropathic pain. However, the effects of PRF on zoster-related trigeminal neuralgia (TN) remain unclear. The purpose of this meta-analysis is to investigate the efficacy and safety of PRF in the management of zoster-related TN.

Patients and Methods

We searched PubMed, Embase, Cochrane Library, Chinese Biomedical Database (CBM), Chinese National Knowledge Infrastructure (CNKI), and Wanfang for randomized controlled trials from their inception to August 2022. The primary clinical outcomes included pain intensity and adverse events. Secondary clinical outcomes included pain remission rate, trigeminal postherpetic neuralgia (TPHN) incidence, rescue analgesic dose, sleep quality, and quality of life (QoL).

Results

Eight studies with 788 participants were included for final analysis. PRF group exhibited lower pain scores (week 1: MD -2.10, 95% CI -3.28 to -0.93, P=0.0005; week 4: MD -1.56, 95% CI -2.60 to -0.51, P=0.003; week 12: MD -1.52, 95% CI -2.68 to -0.35, P=0.01), lower risk of TPHN incidence (RR 0.22, 95% CI 0.06 to 0.81, P=0.02) and better sleep quality (week 4: MD -2.52, 95% CI -3.28 to -1.77, P<0.01; week 12: MD -2.25, 95% CI -2.90 to -1.60, P<0.01) than control group. Besides, pain remission rate (RR 1.08, 95% CI 0.93 to 1.26, P=0.31) and adverse events (RR 0.95, 95% CI 0.71 to 1.27, P=0.74) were comparable in both groups.

Conclusion

PRF is an effective and safe treatment and it yields better effects in pain relief, improvement of sleep quality, and prevention of developing TPHN. Although PRF provides a comparable pain remission rate with the control, it is still a preferred and alternative treatment for relieving zoster-related facial pain.

Burden of opioid use for pain management among adult herpes zoster patients in the US and the potential impact of vaccination

The goal of this research was to describe treatment patterns, health-care resource utilization, and costs for herpes zoster (HZ)-related pain, and to estimate the potential impact of recombinant zoster vaccine (RZV) on avoided HZ cases and HZ-related pain prescriptions. This retrospective claims database study included patients from commercial, Medicare, and Medicaid plans between 2012 and 2017. Subjects with an HZ episode were assigned to three cohorts: “opioid”, “non-opioid”, and “no-treatment” cohorts. Subjects in the opioid cohort were matched to a non-HZ cohort. The potential impact of RZV vaccination on HZ case avoidance and resulting painkiller prescriptions was modeled. Over 25% of subjects with an HZ episode received opioids. Adjusted health-care costs were approximately double in the opioid cohort versus non-opioid or matched non-HZ cohorts. Postherpetic neuralgia, immunocompromised status, and comorbidities increased the risk for opioid prescription. RZV vaccination was predicted to avoid over 19,000 patients from receiving opioid prescriptions for every 1 million adults aged ≥50 years. HZ-related prescriptions of opioids were common and led to increased health care costs. RZV vaccination may potentially reduce opioid prescriptions through decreasing HZ incidence.

PLAIN LANGUAGE SUMMARY

What is the context?

Herpes zoster or shingles and its complications such as postherpetic neuralgia – a painful condition that affects the nerve fibers and skin – may lead to complex pain that can be addressed using opioids in some patients.

The recombinant zoster vaccine (RZV) vaccine prevents shingles and, therefore, may reduce the use of opioids and the negative health outcomes and costs associated with it.

What is new?

In this retrospective medical claims study, including patients between 2012 and 2017, we

evaluated the receipt of pain medication including opioids in herpes zoster patients, and assessed factors associated with opioid prescription.

estimated health care resource utilization and costs associated with opioid use among patients with herpes zoster.

assessed the impact of vaccination on opioid prescriptions.

Among subjects receiving opioids, 78.5% started with a weak opioid dose. Dose escalation was uncommon.

Postherpetic neuralgia, immunocompromised status, and comorbidities are the main risk factors associated with opioid prescription.

Health care costs are almost double in patients with herpes zoster receiving opioids compared with patients without an opioid prescription.

In a population of 1 million adults aged 50 years or older, vaccination with the recombinant zoster vaccine could prevent over 19,000 patients from receiving opioids.

What is the impact?

Prevention of herpes zoster through vaccination may be a highly effective strategy to reduce opioid prescriptions and costs related to pain management in a susceptible population.

Increasing RZV vaccination coverage in adults aged ≥50 years may further reduce potential opioid prescriptions through a decrease in shingles incidence.

Effect of CT-Guided Gasserian Ganglion Block with Local Anesthetics and Steroids on Acute/Subacute Zoster-Related Trigeminal Neuralgia: A Multicenter Retrospective Study

Purpose

To further evaluate the effects of gasserian ganglion block treatment with local anesthetics and steroids on patients with acute/subacute zoster-related trigeminal neuralgia.

Patients and Methods

This is a multicenteric retrospective study which included patients between the ages of 26–92 years, who suffered from acute/subacute zoster-related trigeminal neuralgia and had undergone CT-guided gasserian ganglion block. The medical records of these patients between January 13, 2016 and August 25, 2021 were retrieved, and the patients were followed up for 6 months. Follow-up outcomes were Numerical Rating Scale (NRS) scores, medications and dosage. The effective rate was defined as the number of cases with NRS score reduction of >50%/total number of cases×100% at 12 weeks postoperatively.

Results

The postoperative NRS scores were significantly decreased in all patients (P < 0.05), and NRS scores in acute zoster group were lower than those in subacute zoster group at different time points (P < 0.05). The percentage of patients who had a reduction of medication use value of >50% was 56.4% and the effective rate was 66.7% in all patients, at 3 months after the block treatment. There was no significant difference in the reduction of medication use value of >50% and the effective rates between the two groups. There were no intracranial hemorrhage, infection or other serious adverse effects in either groups.

Conclusion

CT-guided gasserian ganglion block with local anesthetics and steroids can be an effective and safe technique to relieve the pain of acute/subacute zoster-related trigeminal neuralgia.

Methylprednisolone and local anesthetic for Long-term Postherpetic Neuralgia: a meta-analysis

OBJECTIVE

The purpose was to evaluate the efficacy of methylprednisolone combined with local anesthetics on the incidence or intensity of long-term PHN.

METHODS

We have performed comprehensive literature research in PubMed, Web of Science, Cochrane library, and China national knowledge infrastructure (CNKI) databases (inception through October 19, 2021). Relevant randomized controlled trials(RCTs) with long-term duration were included, regardless of the injection method. The indicators were the incidence of PHN and the Visual Analog Scale (VAS) scores.

RESULTS

Five randomized controlled trials with 980 patients were retrieved. Compared with standard treatment (antivirals) alone, the combination of methylprednisolone, local anesthetic and standard treatment exhibited a significant decrease in the incidence of PHN in 1 month (RR =0.38, 95%CI: 0.19 to 0.76), 3 months (RR =0.40, 95%CI: 0.19 to 0.84) and 6 months (RR =0.37, 95%CI: 0.15 to 0.94) after zoster onset. In VAS scores, there was also a significant difference between the two groups in long-term PHN (3 months: WMD=-1.57, 95%CI: -2.84 to -0.30; 6 months: WMD=-0.72, 95%CI: -1.29 to -0.16).

CONCLUSION

The combination of Methylprednisolone, local anesthetic, and standard treatment appears to be an ideal option for patients with PHN. Further investigation is needed for the safety of this therapy.

Acupuncture (superficial dry-needling) as a treatment for chronic postherpetic neuralgia - a randomized clinical trial

BACKGROUND

Postherpetic neuralgia is a painful condition where finding sufficient treatment poses a great challenge. Acupuncture is often used as an alternative treatment for these pains, yet no randomized trials, using a sham-placebo have been performed to confirm its effect. Our objective was to investigate the efficacy of acupuncture compared to sham-acupuncture when treating chronic postherpetic dermal pain.

METHODS

We performed a sham-controlled double-blinded randomized clinical trial (RCT) with two arms. The intervention group received superficial dry-needling, and the control group received sham acupuncture using blunted needles. Twenty-six patients received two treatments. They filled out questionnaires at baseline and 1 month after treatment: (1) average and maximum pain (Numeric Rating Scale), (2) neuropathic pain (Neuropathic Pain Scale Inventory) and (3) Quality of Life (QoL) (Short-form 36).

RESULTS

Thirteen patients were allocated to the intervention group and 15 to the control group. We did not detect any significant changes in levels of pain and neuropathic pain. One QoL parameter, regarding emotional problems, reached a level of statistical significance. The sham-blinding was successful. This is the first RCT on the effect of acupuncture (superficial dry-needling) on postherpetic neuralgia (PHN), using a sham procedure as control. We observed no significant changes or tendencies in the measured levels of pain. One QoL parameter had significant improvement in the intervention group compared to the control group.

CONCLUSION

In conclusion, acupuncture was not superior to treatment with sham acupuncture. Though individual patients may experience some pain relief from acupuncture, our results do not support the routine use of this type of acupuncture to treat PHN.

Early examination of real-world uptake and second-dose completion of recombinant zoster vaccine in the United States from October 2017 to September 2019

Shingrix (Recombinant zoster vaccine, RZV) was approved in October 2017 in the United States (US) for the prevention of herpes zoster in adults aged 50 years and older. The vaccine is administered in two doses, with the second dose administration recommended between two and six months after the first dose. Examination of uptake and series completion is important to ensure appropriate use, especially at the time of vaccine introduction. This report provides demographic characteristics of patients receiving RZV between October 2017 and September 2019, first- and second-dose uptake, and a cumulative estimation of second-dose completion by month for US adults aged 50 years and older. Monthly uptake increased rapidly since October 2017; overall, 7,097,441 first doses of RZV were administered along with 4,277,636 second doses during the observed timeframe. Among people with an observed first-dose administration, 70% and 80% completed the two-dose series within six and 12 months post initial dose, respectively. This evidence suggests that RZV has rapidly been adopted by a large population in the US and most are following manufacturer or policy recommendations regarding series completion. Further analyses are needed to explore potential patient, provider, and policy-relevant characteristics associated with second-dose completion that could serve as targets for further improvement.

External therapy of Chinese medicine for postherpetic neuralgia: A protocol for systematic review and meta-analysis

BACKGROUND

Postherpetic neuralgia (PHN), the most common complication of herpes zoster, brings about a health-care burden at both the individual and societal levels. External therapy of Chinese medicine (ETCM) is an effective treatment of PHN generally available in China, yet there is incomplete evidence to evaluate the efficacy and safety of it.

METHODS

This protocol is based on the previous reporting items. We will search 3 English databases (PubMed, EMBASE, and the Cochrane Library) and 3 Chinese databases (CNKI, CBM, and Wan Fang Database) until January 2020. RCTs to evaluate the efficacy and safety of external therapy of Chinese medicine for postherpetic neuralgia will be included. The primary outcome will be assessed by VAS or NRS. We will use the criteria provided by Cochrane Handbook 5.3.0 for quality evaluation and risk assessment, and use the Revman 5.3 software for meta-analysis.

ETHICS AND DISSEMINATION

Ethical approval is not required for systematic review and meta- analysis. The results of this review will be disseminated in a peer-review journal.

PROSPERO REGISTRATION NUMBER

CRD42020163511.

γ-Aminobutyric Acid and Derivatives Reduce the Incidence of Acute Pain after Herpes Zoster - A Systematic Review and Meta-analysis

Herpes zoster (HZ) causes considerable pain and distress, and γ-Aminobutyric acid (GABA) and its derivatives are assumed to control this, but the available data are inconsistent. This meta-analysis and systematic review aimed to assess the effectiveness of GABA derivatives in the prevention of acute herpetic pain. The metaanalysis was conducted following the PRISMA guidelines using PICO format, registered in PROSPERO number CRD42018095758. PubMed, Web of Science, Ovid, Scopus, and EMBASE databases were searched. Records were included if they were randomized controlled trials of patients undergoing HZ infection, investigating the effect of GABA derivatives versus placebo in the treatment of HZ pain. Eligible trials were evaluated for the risk of bias. Then data were extracted and analysed. The number of patients with observed presence of pain after treatment was used to calculate odds ratio in a random effect model with the DerSimonian-Laird estimator. The I2 statistic was analysed for heterogeneity. The potential risk of bias was measured using Egger's regression test. The meta-analysis included three randomized controlled trials with a total of 297 patients. The incidence of acute HZ pain events for GABA group was significantly lower compared to placebo group,18/148 vs 44/149, respectively (OR = 0.36; 95% CI = 0.14 to 0.93; Z = 2.11; P = 0.035), Egger's test yielded P = 0.308. In conclusion, the present meta-analysis demonstrates that GABA derivatives reduce the incidence of acute herpetic pain. However, additional, well-designed randomized clinical trials are needed to determine their dose- and time-dependency regarding this symptom.

Memantine selectively prevented the induction of dynamic allodynia by blocking Kir2.1 channel and inhibiting the activation of microglia in spinal dorsal horn of mice in spared nerve injury model

Background

Memantine is one of the important clinical medications in treating moderate to severe Alzheimer disease. The effect of memantine on preventing or treating punctate allodynia has been thoroughly studied but not on the induction of dynamic allodynia. The aim of this study is to investigate whether memantine could prevent the induction of dynamic allodynia and its underlying spinal mechanisms.

Results

(1) In in vivo spared nerve injury pain model, pretreatment with memantine at a lower dose (10 nmol, intrathecal; memantine-10) selectively prevented the induction of dynamic allodynia but not the punctate allodynia. (2) Pretreatment with either MK801-10 (MK801-10 nmol, intrathecal) or higher dose of memantine (30 nmol, intrathecal; memantine-30) prevented the induction of both dynamic and punctate allodynia. (3) Memantine-10 showed significant effect on the inhibition of the spared nerve injury-induced overactivation of microglia in spinal dorsal horn. (4) In contrast, in complete freund′s adjuvant (CFA) model, memantine-10 neither affected the CFA injection-induced activation of microglia in spinal dorsal horn nor the induction of dynamic allodynia. (5) Immunohistological studies showed Kir2.1 channel distributed widely and co-localized with microglia in the spinal dorsal horn of mice. (6) Pretreatment with either minocycline, a microglia inhibitor, or ML133, a Kir2.1 inhibitor, both selectively prevented the overactivation of microglia in spinal dorsal horn and the induction of dynamic allodynia following spared nerve injury.

Conclusion

The selective inhibitory effect on the induction of dynamic allodynia in spared nerve injury model by low dose of the memantine (memantine-10) was tightly correlated with the blockade of microglia Kir2.1 channel to suppress the microglia activation.

Efficacy of CT Guided Pulsed Radiofrequency Treatment for Trigeminal Postherpetic Neuralgia

Objectives

Trigeminal postherpetic neuralgia (TPHN) often presents with moderate to severe pain, hyperalgesia, and allodynia. Conventional analgesic treatments are poorly effective, which seriously affects the quality of life. This retrospective study aimed to evaluate the efficacy of pulsed radiofrequency (PRF) for the treatment of TPHN.

Methods

A total of 90 TPHN patients were selected between January 2014 and December 2016 in the Department of Pain Management, Shengjing Hospital, China Medical University. Patients were randomly divided into two groups according to the order of enrollment (n = 45 per group): group A, peripheral nerve (supraorbital nerve, infraorbital nerve and mental nerve) PRF; group B, gasserian ganglion PRF. Follow-up assessments of visual analogue scale (VAS) pain assessment, SF-36 health status questionnaire, total efficiency rate, and drug dosage of anticonvulsants and opioid analgesics were performed at time points of 1 week, 1 month, 3 months, 6 months, and 1 year after surgery.

Results

At each postsurgery time point, the VAS decreased, SF-36 (physical and mental components) increased, and drug dosage of anticonvulsants and opioids analgesics decreased in both treatment groups; values at each time point were significantly different from presurgery values (P < 0.05). Compared with group A, VAS decreased, SF-36 increased, and dosage of anticonvulsants and opioids analgesics decreased significantly in group B (P < 0.05). The total efficiency rates one year after surgery in group A and group B were 68.9 and 86.7%, respectively. The total efficiency rate of group B was statistically higher than that of group A (P < 0.05).

Conclusion

PRF relieved TPHN, and gasserian ganglion PRF was more effective than peripheral nerve PRF. The method was effective and improved the quality of life of the patients. PRF is recommended as a treatment for TPHN.

Parameters associated with efficacy of epidural steroid injections in the management of postherpetic neuralgia: the Mayo Clinic experience

Purpose: Thirty percent of patients with postherpetic neuralgia (PHN) receiving conservative treatment report unsatisfactory pain relief. Epidural steroid injections (ESIs) are commonly used as a therapeutic intervention in these patients. In this study, we aimed to determine if there are variables that predict the efficacy of ESI in patients with PHN.

Patients and methods: We retrospectively identified patients seen at Mayo Clinic who had PHN and received ESI. From their medical records, we abstracted the demographic variables, concurrent medication use, anatomic approach and medication for ESI, and degree of pain relief at 2 and 12 weeks' postintervention.

Results: None of the studied variables were significantly associated with efficacy of ESI in patients with PHN. PHN that began <11 months before treatment was predictive of a response to ESI at 12 weeks postintervention (positive predictive value, 55%). Patients who reported poor ESI efficacy 2 weeks after the intervention had a 94% chance of still having pain at 12 weeks.

Conclusion: For this cohort of patients with PHN being treated with ESI, no demographic characteristics, concurrently used medications, or type of ESI were associated with ESI treatment efficacy at 2 or 12 weeks after the intervention.

Open-Label Single-Dose Study to Assess the Effect of Mild and Moderate Hepatic Impairment on the Pharmacokinetics of Mirogabalin

BACKGROUND AND OBJECTIVES

Mirogabalin is an α₂δ ligand being developed to treat neuropathic pain. A small fraction of mirogabalin is metabolized by the liver, where hepatic impairment may affect exposure. The objective of this phase I, open-label single-dose study was to determine if mild or moderate hepatic impairment alters the pharmacokinetics of mirogabalin.

METHODS

Serial blood samples were collected for determination of maximum observed concentration, time to maximum concentration, and area under the concentration-time curve until the last quantifiable concentration of the active free form (A200-700) and inactive lactam metabolite (A204-4455) of mirogabalin.

RESULTS

The A200-700 maximum observed concentration was similar in subjects with mild hepatic impairment but lower in subjects with moderate hepatic impairment vs. control subjects. The A204-4455 maximum observed concentration was lower in subjects with mild and moderate hepatic impairment vs. control groups. The A200-700 area under the concentration-time curve until the last quantifiable concentration was slightly lower in subjects with mild hepatic impairment and slightly higher in subjects with moderate hepatic impairment vs. control subjects. Peak A204-4455 levels were approximately 22% and 31% lower for subjects with mild and moderate hepatic impairment vs. control individuals, respectively. Exposure to A204-4455 was approximately 37% lower in subjects with mild hepatic impairment but unaffected in subjects with moderate hepatic impairment vs. control groups. Two subjects in the mild hepatic impairment group reported a treatment-emergent adverse event of mild somnolence. No serious or severe treatment-emergent adverse events, discontinuations as a result of treatment-emergent adverse events, or deaths were reported.

CONCLUSIONS

Mild hepatic impairment resulted in lower A200-700 and A204-4455 exposure, while moderate hepatic impairment did not affect A200-700 exposure. Overall, mild-to-moderate hepatic impairment did not have a significant effect on mirogabalin exposure. A single 15-mg dose of mirogabalin was well tolerated by subjects with mild or moderate hepatic impairment.

Post-herpetic neuralgia - a review of current management and future directions

Post-herpetic neuralgia (PHN) is common and treatment is often suboptimal with less than half of patients achieving adequate 50% pain relief. As an area of unmet clinical need and as an archetype of neuropathic pain, it deserves the attention of clinicians and researchers. Areas covered: This review summarises the epidemiology, pathophysiology, risk factors and clinical features of varicella infection. It describes the current and possible future management strategies for preventing varicella infection and reactivation and for treating PHN. Expert opinion: A highly successful Varicella Zoster (VZV) vaccine has not been universally adopted due to fears that it may increase Herpes Zoster (HZ) incidence - and thus PHN - in older, unvaccinated generations. This is a controversial theory but advances in the efficacy of vaccines against HZ may allay these fears and encourage more widespread adoption of the VZV vaccine. Treatment of PHN, as for any neuropathic pain, must be multidisciplinary and multimodal. Advances in sensory phenotyping technology and genomics may allow more individualised treatment. Traditional research methodologies are ill-suited to assess the kind of complex interventions that are necessary to achieve better clinical outcomes in this challenging field.

Adverse Effects of Antidepressants for Chronic Pain: A Systematic Review and Meta-analysis

Background

Antidepressants are widely used in the treatment of chronic pain. Applied doses are lower than those needed to unfold an antidepressive effect. While efficacy of antidepressants for chronic pain has been reported in large randomized-controlled trials (RCT), there is inconsistent data on adverse effects and tolerability. We aimed at synthesizing data from RCT to explore adverse effect profiles and tolerability of antidepressants for treatment of chronic pain.

Methods

Systematic literature research and meta-analyses were performed regarding side effects and safety of different antidepressants in the treatment of chronic pain according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The National Center for Biotechnology Information library and MEDLINE were searched. Randomized placebo-controlled trials were included in quantitative data synthesis.

Results

Out of 1,975 screened articles, 33 papers published between 1995 and 2015 were included in our review and 23 studies were included in the meta-analyses. A higher risk for adverse effects compared to placebo was observed in all antidepressants included in our analyses, except nortriptyline. The most prevalent adverse effects were dry mouth, dizziness, nausea, headache, and constipation. Amitriptyline, mirtazapine, desipramine, venlafaxine, fluoxetine, and nortriptyline showed the highest placebo effect-adjusted risk of adverse effects. Risk for withdrawal due to adverse effects was highest in desipramine (risk ratio: 4.09, 95%-confidence interval [1.31; 12.82]) followed by milnacipran, venlafaxine, and duloxetine. The most common adverse effects under treatment with antidepressants were dry mouth, dizziness, nausea, headache, and constipation followed by palpitations, sweating, and drowsiness. However, overall tolerability was high. Each antidepressant showed distinct risk profiles of adverse effects.

Conclusion

Our synthesized data analysis confirmed overall tolerability of low-dose antidepressants for the treatment of chronic pain and revealed drug specific risk profiles. This encompassing characterization of adverse effect profiles might be useful in defining multimodal treatment regimens for chronic pain which also consider patients’ comorbidities and co-medication.

The 5% Lidocaine-Medicated Plaster: Its Inclusion in International Treatment Guidelines for Treating Localized Neuropathic Pain, and Clinical Evidence Supporting its Use

When peripheral neuropathic pain affects a specific, clearly demarcated area of the body, it may be described as localized neuropathic pain (LNP). Examples include postherpetic neuralgia and painful diabetic neuropathy, as well as post-surgical and post-traumatic pain. These conditions may respond to topical treatment, i.e., pharmaceutical agents acting locally on the peripheral nervous system, and the topical route offers advantages over systemic administration. Notably, only a small fraction of the dose reaches the systemic circulation, thereby reducing the risk of systemic adverse effects, drug–drug interactions and overdose. From the patient’s perspective, the analgesic agent is easily applied to the most painful area(s). The 5% lidocaine-medicated plaster has been used for several years to treat LNP and is registered in approximately 50 countries. Many clinical guidelines recommend this treatment modality as a first-line option for treating LNP, particularly in frail and/or elderly patients and those receiving multiple medications, because the benefit-to-risk ratios are far better than those of systemic analgesics. However, some guidelines make only a weak recommendation for its use. This paper considers the positioning of the 5% lidocaine-medicated plaster in international treatment guidelines and how they may be influenced by the specific criteria used in developing them, such as the methodology employed by randomized, placebo-controlled trials. It then examines the body of evidence supporting use of the plaster in some prevalent LNP conditions. Common themes that emerge from clinical studies are: (1) the excellent tolerability and safety of the plaster, which can increase patients’ adherence to treatment, (2) continued efficacy over long-term treatment, and (3) significant reduction in the size of the painful area. On this basis, it is felt that the 5% lidocaine-medicated plaster should be more strongly recommended for treating LNP, either as one component of a multimodal approach or as monotherapy.

Chronic Pruritus in the Absence of Skin Disease: Pathophysiology, Diagnosis and Treatment

Chronic pruritus arises not only from dermatoses, but also, in up to half of cases, from extracutaneous origins. A multitude of systemic, neurological, psychiatric, and somatoform conditions are associated with pruritus in the absence of skin disease. Moreover, pruritus is a frequently observed side effect of many drugs. It is therefore difficult for physicians to make a correct diagnosis. Chronic pruritus patients frequently present to the dermatologist with skin lesions secondary to a long-lasting scratching behavior, such as lichenification and prurigo nodularis. A structured clinical history and physical examination are essential in order to evaluate the pruritus, along with systematic, medical history-adapted laboratory and radiological tests carried out according to the differential diagnosis. For therapeutic reasons, a symptomatic therapy should be promptly initiated parallel to the diagnostic procedures. Once the underlying factor(s) leading to the pruritus are identified, a targeted therapy should be implemented. Importantly, the treatment of accompanying disorders such as sleep disturbances or mental symptoms should be taken into consideration. Even after successful treatment of the underlying cause, pruritus may persist, likely due to chronicity processes including peripheral and central sensitization or impaired inhibition at spinal level. A vast arsenal of topical and systemic agents targeting these pathophysiological mechanisms has been used to deter further chronicity. The therapeutic options currently available are, however, still insufficient for many patients. Thus, future studies aiming to unveil the complex mechanisms underlying chronic pruritus and develop new therapeutic agents are urgently needed.

Issues in the Treatment of Neurological Conditions Caused by Reactivation of Varicella Zoster Virus (VZV)

Varicella zoster virus (VZV) is a ubiquitous neurotropic human herpesvirus. Primary infection usually causes varicella (chicken pox), after which virus becomes latent in ganglia along the entire neuraxis. Decades later, virus reactivates to produce herpes zoster (shingles), a painful dermatomally distributed vesicular eruption. Zoster may be further complicated by postherpetic neuralgia, VZV vasculopathy, myelitis, and segmental motor weakness. VZV reactivation has also been associated with giant cell arteritis. This overview discusses treatment of various conditions that often require both corticosteroids and antiviral drugs. Treatment for VZV-associated disease is often based on case reports and small studies rather than large-scale clinical trials. Issues that require resolution include the optimal duration of such combined therapy, more effective treatment for postherpetic neuralgia, whether some treatments should be given orally or intravenously, the widening spectrum of zoster sine herpete, and the role of antiviral therapy in giant cell arteritis.

A pharmacological treatment algorithm for localized neuropathic pain

Neuropathic pain is caused by a lesion or disease affecting the somatosensory system and is difficult to manage, often proving refractory to existing treatments. In more than half of cases, it is localized and affects a specific, clearly circumscribed area of the body (localized neuropathic pain, or LNP). A recently developed screening tool enables patients with probable neuropathic pain/LNP to be identified quickly and easily. In view of the conflicting current treatment recommendations, an advisory board of pain specialists met in June 2015 to develop a complementary treatment guidance algorithm, for use in the primary care setting and by non-pain specialists. The starting point of the algorithm is a diagnosis of LNP and there was consensus that first-line treatment should be a topical analgesic agent, because the benefit/risk ratios are far better than for systemic agents. Topical application offers site-specific delivery, a lower total systemic dose and avoidance of first-pass metabolism, reducing the risk of adverse events and drug/drug interactions. The 5% lidocaine medicated plaster has most evidence supporting its use in LNP, producing effective analgesia and reducing the associated area of allodynia, but other topical agents include capsaicin, clonidine and botulinum toxin type A. Treatment should be commenced with the topical agent of choice, and the patient re-assessed after an appropriate period. Where the response is good the topical agent is continued, with a re-evaluation after 3-6 months. A systemic agent (e.g. gabapentin, pregabalin, duloxetine, venlafaxine) is added if there is only a partial response, or substituted if there is no response, and the patient re-assessed after a month. If there is poor or no response to the systemic agent the patient should be switched to an alternative one and, if this also proves ineffective, referred to a pain specialist.

5% lidocaine medicated plasters vs. sympathetic nerve blocks as a part of multimodal treatment strategy for the management of postherpetic neuralgia: a retrospective, consecutive, case-series study

INTRODUCTION

5% lidocaine medicated plasters (5% LMP) have been appointed as a first-line treatment for post-herpetic neuralgia (PHN), while formerly used sympathetic nerve blocks (SNBs) were recently denied their clinical efficacy. The aim of this study was to compare the results of PHN management with the use of SNBs and 5% LMP as a first-line treatment.

MATERIAL AND METHODS

This study was designed as a retrospective, consecutive, case-series study. Data of 60 consecutive PHN patients with allodynia treated with the use of SNBs and 60 subsequent patients managed with 5% LMP were analyzed. Pain severity after 8 weeks was assessed to recognize the results of the implemented therapy, with numeric rating scale (NRS) score <3 or =3 considered a success. Additionally, the number of pain-free patients (NRS=0) after 8 weeks were identified in both groups and compared.

RESULTS

The rate of failures in SNBs and 5% LMP group was similar (18.9% vs. 27.1% of poor treatment results, respectively), with the average change in NRS of 5.88 ± 2.41 in nerve blocks and 5.01 ± 1.67 in lidocaine group (p=0.02). Significant difference was also noted in the rates of pain-free patients: 20 patients (34.4%) treated with SNBs and 8 (13.5%) using 5% LMP were pain-free after 8 weeks of treatment.

CONCLUSION

It may be concluded that SNBs may still be considered useful in PHN management, as it appears that in some cases this mode of treatment may offer some advantages over 5% LMP.

Neuropathic pruritus

Pruritus, also known as itch, is a very common, unpleasant sensation that elicits an urge to scratch. Its origin is not always in the skin, and neuropathic itch that is caused by neuronal or glial damage is common, but poorly understood by both dermatologists and neurologists. Although pruritus has not been considered as serious a symptom as pain, it is difficult to treat and--if chronic--can severely impair quality of life. Neuropathic itch is often associated with other clinical symptoms, most commonly neuropathic pain, and hypersensitization to stimuli is present in both pruritus and pain of neuropathic origin. The shared aetiology can aid in finding suitable treatment for itch in some cases, but more detailed knowledge of the mechanisms of itch, along with standardized, well-controlled trials, is needed. Pruritus research is an emerging but currently very active field, and our understanding of this sensation is rapidly increasing. Here, we review new discoveries regarding the role of the nervous system and the contribution of different pathways in pruritus, discuss the different aetiologies of neuropathic itch, and outline currently available and potential strategies for managing neuropathic pruritus.

Varicella zoster: an update on current treatment options and future perspectives

INTRODUCTION

Varicella zoster virus is a highly contagious virus that causes a primary infection known as varicella (chickenpox) that may reactivate years later to cause herpes zoster (HZ or shingles). After shingles heal, patients may develop post-herpetic neuralgia (PHN), neuropathic pain syndrome that can cause significant suffering for years and is often refractory to treatment.

AREAS COVERED

The wide range of treatment and management options for varicella, HZ and PHN are reviewed and discussed. PubMed was the database used for the literature search.

EXPERT OPINION

Antiviral therapy effectively treats acute varicella and HZ. However, PHN is still difficult to manage, especially with the numerous treatment measures that do not work consistently in all patients. The best approach is to prevent the complication from occurring in the first place by preventing HZ with the HZ vaccine, which have decreased the burden of illness caused by VZ and the incidence of HZ. Unlike the varicella vaccine, the uptake for the HZ vaccine is very low and thereby more patients over the age of 50 years should be encouraged to receive the vaccine to reduce the risk of developing HZ. Initiating treatment with gabapentin and antiviral concomitantly as soon as the rash develops may reduce the severity of complications but there is a lack of data showing these medications preventing the development of PHN.

Effects of dorsal root ganglion destruction by adriamycin in patients with postherpetic neuralgia

PURPOSE

To investigate the effects of dorsal root ganglion destruction in patients with postherpetic neuralgia (PHN).

METHODS

Seventy-two patients with PHN selected were randomly divided into two groups (n=36). Group A was the control group (treated by injection) and group B was the group of dorsal root ganglion destruction by adriamycin. Visual analog scale scores (VAS), SAS, SF-MPQ scores. Clinical effects and therapy safety were evaluated before therapy, one week, three and six months after therapy. Forty-four patients were available for intention-to-treat analysis.

RESULTS

The average pain scores on the Likert scale were significantly reduced at each point in group B. Patients in group B reported clinical effectiveness at six months as excellent response, good response, improved but unsatisfactory or unchanged 16, 12 and 8.VAS scores at each time point after the operation were lower than that before operation and in group A, there was significant difference. Patients showed significant improvement in sleep scores in group B. There was significant difference at T2 in group A than T1. There was no significant difference in group A at T3, T4 after the operation than that before operation. Between group comparison: there was significant difference between group A and group B at each time point after the operation.

CONCLUSIONS

Dorsal root ganglion destruction by adriamycin under guidance of C-arm perspective, the puncture operation was accurate without any adverse reaction or serious complications, which could effectively relieve pain of patients with postherpetic neuralgia, but the long-term effects needed further study.

Gabapentin for once-daily treatment of post-herpetic neuralgia: a review

Post-herpetic neuralgia is a neuropathic pain syndrome resulting from an insult to the peripheral and central nervous systems caused by the varicella zoster virus. Spontaneous pain may result in the persistent sensation of burning, tingling, or aching and may be associated with thermally or mechanically provoked pain, resulting in hyperalgesia or allodynia. The majority of cases occur in patients over the age of 50 years. Gabapentin is a structural analog of gamma aminobutyric acid that binds to the α₂-δ site of voltage-dependent calcium channels and modulates the influx of calcium, with a resulting reduction in excitatory neurotransmitter release. Gabapentin is effective in reducing neuropathic pain due to post-herpetic neuralgia when given at least three times per day, due to its short half-life, resulting in demonstrable fluctuations in plasma levels. Gabapentin has dose-limiting side effects that prevent some patients from achieving therapeutic plasma levels, such as somnolence (27.4%), dizziness (23.9%), and ataxia (7.1%). Gralise™ is a once-daily extended-release formulation of gabapentin that has been developed using AcuForm™ technology. AcuForm is a polymer-based drug delivery system that retains the tablet in the stomach and upper gastrointestinal tract for a sustained period of time. Once-daily dosing has been shown to provide comparable drug exposure with an identical daily dose of the immediate-release formulation when administered three times daily. Participants given Gralise 1800 mg daily had a statistically significant reduction in average daily pain intensity scores compared with placebo, reduced sleep interference due to pain, and a greater percent of participants reporting being much or very much improved on the patient global impression of change. An analysis comparing the efficacy and safety profiles in the aging population (≥65 years) with those younger than 65 years showed that Gralise is effective and well tolerated in both age groups.

Review of current guidelines on the care of postherpetic neuralgia

An unfortunate minority of patients with acute herpes zoster (AHZ) experience pain beyond the typical 4-week duration, and roughly 10% develop the distressing complication of postherpetic neuralgia (PHN), often defined as pain persisting for > 4 months after the onset of the rash. Elderly patients are at increased risk of PHN. The pathophysiology of PHN is complex, likely involving both peripheral and central processes. This complexity may create opportunities for pharmacologic interventions with multiple differing mechanisms of action. Consequently, complementary combinations of pharmacologic agents are frequently more effective than any monotherapy. Current US and international guidelines on the care of patients with PHN are reviewed and interpreted here to facilitate their effective incorporation into the practice of primary care physicians, acknowledging the contrasts that often exist between the clinical trial populations analyzed to craft so-called evidence-based medicine and the individual patients seen in daily practice, many of whom may not have been candidates for those clinical trials. First-line treatments for PHN include tricyclic antidepressants, gabapentin and pregabalin, and the topical lidocaine 5% patch. Opioids, tramadol, capsaicin cream, and the capsaicin 8% patch are recommended as either second- or third-line therapies in different guidelines. Therapies that have demonstrated effectiveness for other types of neuropathic pain are discussed, such as serotonin-norepinephrine reuptake inhibitors, the anticonvulsants carbamazepine and valproic acid, and botulinum toxin. Invasive procedures such as sympathetic blockade, intrathecal steroids, and implantable spinal cord stimulators have been studied for relief of PHN, mainly in patients refractory to noninvasive pharmacologic interventions. The main guidelines considered here are those issued by the American Academy of Neurology for the treatment of postherpetic neuralgia (2004) and general guidelines for the treatment of neuropathic pain issued by the Special Interest Group on Neuropathic Pain of the International Association for the Study of Pain (2007) and the European Federation of Neurological Societies (2010).

His-story or her-story: deconstruction of the concepts of somatization towards a new approach in advanced nursing practice care

PURPOSE

This article will endeavor to present an alternative view of somatoform disorders, assist in understanding the possible underlying comorbid psychiatric symptoms, and identify psychopharmacological options for treatment.

CONCLUSIONS

Recognizing symptom clusters is a useful strategy when considering psychotropic options for treatment and management.

PRACTICE IMPLICATIONS

The alternative strategies presented and discussed in this article can contribute to a useful and positive experience for both the clinician and the individual suffering from medically unexplained physical symptoms as they promote the care, health, and well-being of the individual rather than a cure, illness, and/or disease state that needs rendering, mending, and/or surgery.

A double-blind, placebo-controlled trial of a topical treatment for chemotherapy-induced peripheral neuropathy: NCCTG trial N06CA

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is a troublesome chronic symptom that has no proven pharmacologic treatment. The purpose of this double-blind randomized placebo-controlled trial was to evaluate a novel compounded topical gel for this problem.

METHODS

Patients with CIPN were randomized to baclofen 10 mg, amitriptyline HCL 40 mg, and ketamine 20 mg in a pluronic lecithin organogel (BAK-PLO) versus placebo (PLO) to determine its effect on numbness, tingling, pain, and function. The primary endpoint was the baseline-adjusted sensory subscale of the EORTC QLQ-CIPN20, at 4 weeks.

RESULTS

Data in 208 patients reveal a trend for improvement that is greater in the BAK-PLO arm over placebo in both the sensory (p = 0.053) and motor subscales (p = 0.021). The greatest improvements were related to the symptoms of tingling, cramping, and shooting/burning pain in the hands as well as difficulty in holding a pen. There were no undesirable toxicities associated with the BAK-PLO and no evidence of systemic toxicity.

CONCLUSION

Topical treatment with BAK-PLO appears to somewhat improve symptoms of CIPN. This topical gel was well tolerated, without evident systemic toxicity. Further research is needed with increased doses to better clarify the clinical role of this treatment in CIPN.

The use of vitamin E for the prevention of chemotherapy-induced peripheral neuropathy: results of a randomized phase III clinical trial

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) continues to be a substantial problem for many cancer patients. Pursuant to promising appearing pilot data, the current study evaluated the use of vitamin E for the prevention of CIPN.

METHODS

A phase III, randomized, double-blind, placebo-controlled study was conducted in patients undergoing therapy with neurotoxic chemotherapy, utilizing twice daily dosing of vitamin E (400 mg)/placebo. The primary endpoint was the incidence of grade 2+ sensory neuropathy (SN) toxicity (CTCAE v 3.0) in each treatment arm, analyzed by chi-square testing. Planned sample size was 100 patients per arm to provide 80% power to detect a difference in incidence of grade 2+ SN toxicity from 25% in the placebo group to 10% in the vitamin E group.

RESULTS

Two-hundred seven patients were enrolled between December 1, 2006 and December 14, 2007, producing 189 evaluable cases for analysis. Cytotoxic agents included taxanes (109), cisplatin (8), carboplatin (2), oxaliplatin (50), or combination (20). There was no difference in the incidence of grade 2+ SN between the two arms (34%-vitamin E, 29%-placebo; P = 0.43). There were no significant differences between treatment arms for time to onset of neuropathy (P = 0.58), for chemotherapy dose reductions due to neuropathy (P = 0.21), or for secondary endpoints derived from patient-reported neuropathy symptom assessments. The treatment was well tolerated overall.

CONCLUSIONS

Vitamin E did not appear to reduce the incidence of sensory neuropathy in the studied group of patients receiving neurotoxic chemotherapy.

Post-herpetic neuralgia: 5% lidocaine medicated plaster, pregabalin, or a combination of both? A randomized, open, clinical effectiveness study

OBJECTIVE

To compare efficacy and safety of 5% lidocaine medicated plaster with pregabalin in patients with post-herpetic neuralgia (PHN), and to assess the benefits of combining both drugs in patients not responding to either single agent.

STUDY DESIGN AND METHODS

This was a two-stage adaptive, randomised, open-label, multicentre, non-inferiority study (NCT 00414349). The subset of patients with PHN is reported here. Patients with an absolute value of >4 on the NRS-3 were randomly assigned to 4-week treatment with 5% lidocaine medicated plaster or twice-daily pregabalin capsules titrated to effect. Subsequently, patients sufficiently treated with monotherapy (patients with NRS-3 <or=4 at 4 weeks or a reduction on the NRS-3 from baseline of >or=2 points) continued with monotherapy; patients insufficiently treated with monotherapy received both drugs in combination for 8 weeks.

OUTCOME MEASURES

Pain according to SF-MPQ and NPSI, onset of effect, reduction in worst pain on the NRS; allodynia severity; quality of life (QoL) based on EQ-5D, SF-36; PGIC; rescue medication intake; adverse events (AEs) monitoring.

RESULTS

At 4 weeks, SF-MPQ total scores improved by -7.6 +/- 6.66 (mean +/- SD) under 5% lidocaine medicated plaster and by -5.3 +/- 7.93 under pregabalin. NPSI total scores declined by -1.6 +/- 1.73 under 5% lidocaine medicated plaster and -1.4 +/- 1.87 under pregabalin. Lidocaine plaster was also effective in reducing worst pain and showed a fast onset of effect. During combination treatment, SF-MPQ and NPSI scores, allodynia, EQ-5D and PGIC improved. Incidences of AEs were in line with previous reports for the two treatments and combination therapy was generally well-tolerated.

CONCLUSIONS

Although this open-label study is lacking a placebo control group, the results suggest that 5% lidocaine medicated plaster is at least as effective as pregabalin for pain relief in PHN, with a favourable safety profile and a resulting positive benefit-risk ratio. In patients unresponsive to either monotherapy, combination therapy provides additional efficacy and is well-tolerated.

Blockade of glycine transporter (GlyT) 2, but not GlyT1, ameliorates dynamic and static mechanical allodynia in mice with herpetic or postherpetic pain

Glycine is an inhibitory neurotransmitter in the spinal dorsal horn and its extracellular concentration is regulated by glial glycine transporter (GlyT) 1 and neuronal GlyT2. This study was conducted to elucidate the effects of intrathecal injections of GlyT1 and GlyT2 inhibitors on two distinct types of mechanical allodynia, dynamic and static allodynia, in mice with herpetic or postherpetic pain. The GlyT2 inhibitor ALX1393, but not the GlyT1 inhibitor sarcosine, suppressed dynamic and static allodynia at the herpetic and postherpetic stages. Intrathecal ALX1393 suppressed dynamic allodynia induced by intrathecal strychnine and N-methyl-D-aspartate (NMDA). Intrathecal sarcosine suppressed dynamic allodynia induced by intrathecal strychnine, but not NMDA. Expression level of GlyT1, but not GlyT2, mRNA in the lumbar dorsal horn was decreased at the herpetic and postherpetic stages. Glycine receptor alpha1-subunit mRNA was decreased in the lumbar dorsal horn at the herpetic, but not postherpetic stage, without alteration in alpha3-subunit mRNA. The results suggest that GlyT2 is a potential target for treatment of dynamic and static allodynia in patients with herpes zoster and postherpetic neuralgia. The lack of efficacy of GlyT1 inhibitor may be explained by activation of NMDA receptors and the down-regulation of GlyT1 in the lumbar dorsal horn.

Transcutaneous electroporation mediated delivery of doxepin-HPCD complex: a sustained release approach for treatment of postherpetic neuralgia

The electroporation mediated transdermal delivery (Protocol - 120 V, 10 ms, 30 pulses at 1 Hz with post pulse waiting period of 20 min) of doxepin using pure drug solution (PDS) and doxepin-hydroxypropyl-beta-cyclodextrin (HPCD) complex solution (CDS) was studied using porcine epidermis model. The stoichiometry of drug-HPCD inclusion complex was determined by differential scanning calorimetry (DSC). The amount of doxepin retained in the epidermis following electroporation did not differ significantly between PDS and CDS. When the drug loaded epidermis was subjected to "Release studies", doxepin release attained a plateau within approximately 2.5 days in case of PDS, whereas in case of CDS, doxepin release was prolonged up to 5 days. Mechanistic studies across the nonbiological barriers demonstrated that the slow dissociation of complex was responsible for sustained release of drug from the epidermis. Pharmacodynamic studies were carried out by electroporation mediated delivery of CDS and PDS in hairless rats. The analgesic effect of doxepin was prolonged in case of CDS as compared to PDS.

Postherpetic neuralgia in the elderly

Postherpetic neuralgia (PHN) is the most common complication of herpes zoster (HZ) or 'shingles' and affects a significant proportion of HZ patients with the disease, with the elderly being most frequently and seriously affected. Characterised by various types of pain (constant, intermittent and stimulus evoked) that persist between 3 months and many years after the resolution of the HZ rash, PHN can have a severe impact on the patient's quality of life and functional ability. PHN remains highly resistant to current treatments. In this review, we discuss the epidemiology, clinical features and management of PHN in the elderly and the potential of vaccination against varicella zoster virus as a means to prevent HZ, and thus decrease the incidence and severity of PHN.