Investigational Drugs for the Treatment of Postherpetic Neuralgia: Systematic Review of Randomized Controlled Trials

Ultrasound-guided thoracic paravertebral injection of dexamethasone palmitate combined with ropivacaine for the treatment of thoracic herpes zoster-related pain: protocol for a prospective, randomized controlled, single-center study

Background

Herpes zoster (HZ) patients often experience herpes zoster-associated pain (ZAP). Thoracic paravertebral nerve block has been proven effective in relieving ZAP and reducing the incidence of postherpetic neuralgia (PHN). Compared to dexamethasone, dexamethasone palmitate (DXP) has stronger anti-inflammatory effects, a longer duration of action, and fewer adverse reactions. This study evaluates the efficacy and safety of ultrasound-guided thoracic paravertebral injection of DXP combined with ropivacaine for treating thoracic ZAP, compared to traditional famciclovir therapy.

Methods

This prospective, randomized, controlled, open-label, endpoint-blinded, single-center trial will recruit 254 patients with ZAP. Patients will be randomly assigned in a 1:1 ratio to the intervention group (thoracic paravertebral injections of DXP combined with ropivacaine and antiviral therapy) or the control group (antiviral therapy). Assessments will include pain intensity, quality of life, sleep quality, inflammatory markers, and adverse events.

Ethics and registration

This study strictly adheres to the 2013 SPIRIT Statement and the Declaration of Helsinki and has been approved by the Ethics Committee of the Second Affiliated Hospital of Guangxi Medical University (Approval Number: 2024-KY(0505)). This clinical trial is registered on the Chinese Clinical Trial Registry platform (ChiCTR) at https://www.chictr.org.cn/index.html (ChiCTR2400087273), registered on 2024-07-24. The results will be disseminated through scientific journals and conferences, aiming to provide evidence supporting the global management of ZAP. The study is expected to start on 1 August 2024, and continue until 31 July 2027.

Different Acupuncture Therapies for Postherpetic Neuralgia: An Overview of Systematic Reviews and Meta-analysis

BACKGROUND

Postherpetic neuralgia (PHN) is the most common complication of herpes zoster infection and affects patients' quality of life. Acupuncture therapy is regarded as a competitive method of treatment for analgesia.

OBJECTIVE

To summarize evidence from systematic reviews (SRs) and evaluate the effectiveness and safety of different acupuncture therapies for treating PHN.

METHODS

Eight electronic databases were searched from their inception to August 5, 2022, including 4 international electronic databases (PubMed, EMBASE, the Cochrane Library, and Web of Science) and 4 Chinese databases (Chinese Biomedical Database, China National Knowledge Infrastructure, VIP Database and Wanfang Database). Methodological quality was assessed by A Measurement Tool to Assess Systematic Reviews 2 (AMSTAR 2). The Risk of Bias in Systematic Review (ROBIS) tool was used to assess the risk of bias in SRs. Evidence level was assessed by the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

RESULTS

Totally, 7 SRs were included, including 128 studies and 9,792 patients. In AMSTAR 2, most of the SRs were of low or critically low levels since they had more than 1 critical deficiency. In ROBIS, 1 SR (14.29%) was rated as high risk, and the other 6 (85.71%) were rated as low risk. In the GRADE system, 9 outcomes (28.13%) were valued as high level, 5 (15.63%) as moderate level, 1 (3.13%) as low, and 17 (53.13%) as very low. In the effectiveness of acupuncture therapy, the group "moxibustion vs. original medical treatment" [mean difference (MD)=-1.44, 95% confidence interval (CI): -1.80 to -1.08, I2=99%, P<0.00001] was of the highest heterogeneity and the group "bloodletting vs. original medical treatment" (MD=-2.80, 95% CI: -3.14 to -2.46, I2=0, P<0.00001) was of the lowest heterogeneity. Six SRs have reported the safety of their studies and no serious events were shown in the treatment and control groups.

CONCLUSIONS

Acupuncture therapy seems to be effective in treating PHN. Despite the evidence that suggested the advantages of acupuncture therapy in relieving pain and promoting efficacy and safety, the methodological quality was quite low. Further studies should pay more attention to the quality of original studies and evidence for SRs to confirm these findings. (PROSPERO registration No. CRD42022344790).

Effectiveness and Safety of Gabapentin versus Pregabalin in the Treatment of Postherpetic Neuralgia: A Retrospective Cohort Study

Aims/Background Postherpetic neuralgia (PHN) is a common chronic pain disease that persists after the rash (clusters of clear blisters on the surface of the skin) has healed, adversely affecting the quality of life of affected patients. Gabapentin (GPT) and pregabalin (PGB) are two commonly used drugs for the treatment of PHN, but there have been broad concerns regarding their efficacy and safety. Thus, this retrospective cohort study was conducted to investigate the effectiveness and safety of GPT versus PGB in the treatment of PHN. Methods A total of 150 patients with PHN receiving routine antiviral and neurotrophic therapies, admitted between January 2022 and November 2023, were selected. 71 patients who were treated with GPT were included in the control group, while the remaining 79 patients who were given PGB were categorized in the observation group. Information on clinical effectiveness, safety (xerostomia, drowsiness, blurred vision, ataxia, and dizziness), analgesic effect (Visual Analogue Scale [VAS] and time to pain relief), sleep quality (Sleep Quality Scale [SQS] and Pittsburgh Sleep Quality Index [PSQI]), and adverse emotions (Self-rating Anxiety/Depression Scale [SAS/SDS]) was collected for analysis. Results Compared to the control group, the observation group exhibited significantly higher clinical effectiveness of PGB in the treatment of PHN (p < 0.05). In other aspects, the overall incidence of adverse events such as xerostomia, drowsiness, blurred vision, ataxia, and dizziness (p > 0.05) was equivalent in these two groups. In addition, significantly lower VAS, SQS, PSQI, SAS, and SDS scores were observed in the observation group after treatment, compared with the control group (p < 0.05). The observation group showed evidently shorter time to pain relief than the other group (p < 0.05). Conclusion PGB is an effective and safe medication for the treatment of PHN, by improving the analgesic effect and sleep quality, and alleviating negative emotions.

P2X3 and P2X2/3 receptors inhibition produces a consistent analgesic efficacy: A systematic review and meta-analysis of preclinical studies

BACKGROUND

P2X3 and P2X2/3 receptors are promising therapeutic targets for pain treatment and selective inhibitors are under evaluation in ongoing clinical trials. Here we aim to consolidate and quantitatively evaluate the preclinical evidence on P2X3 and P2X2/3 receptors inhibitors for pain treatment.

METHODS

A literature search was conducted in PubMed, Scopus and Web-of-Science on August 5, 2023. Data was extracted and meta-analyzed using a random-effects model to estimate the analgesic efficacy of the intervention; then several subgroup analyses were performed.

RESULTS

67 articles were included. The intervention induced a consistent pain reduction (66.5 [CI95% = 58.5, 74.5]; p < 0.0001), which was highest for visceral pain (114.3), followed by muscle (79.8) and neuropathic pain (71.1), but lower for cancer (64.1), joint (57.5) and inflammatory pain (49.0). Further analysis showed a greater effect for mechanical hypersensitivity (70.4) compared to heat hypersensitivity (64.5) and pain-related behavior (54.1). Sex (male or female) or interspecies (mice or rats) differences were not appreciated (p > 0.05). The most used molecule was A-317491, but other such as gefapixant or eliapixant were also effective (p < 0.0001 for all). The analgesic effect was higher for systemic or peripheral administration than for intrathecal administration. Conversely, intracerebroventricular administration was not analgesic, but potentiated pain.

CONCLUSION

P2X3 and P2X2/3 receptor inhibitors showed a good analgesic efficacy in preclinical studies, which was dependent on the pain etiology, pain outcome measured, the drug used and its route of administration. Further research is needed to assess the clinical utility of these preclinical findings.

PROTOCOL REGISTRATION

PROSPERO ID CRD42023450685.

LanCL1 protects developing neurons from long-term isoflurane anesthesia-induced neurotoxicity

Research has revealed that prolonged or repeated exposure to isoflurane, a common general anesthetic, can lead to cognitive and behavioral deficiencies, particularly in early life. The brain contains a wealth of LanCL1, an antioxidant enzyme that is thought to mitigate oxidative stress. Nevertheless, its precise function in mammals remains uncertain. This study uncovered a decrease in the expression of LanCL1 due to prolonged isoflurane anesthesia, accompanied by anesthesia-induced neurotoxicity in vivo and in vitro. To better understand LanCL1's essential function, LanCL1 overexpressing adenoviruses were employed to increase LanCL1 levels. The outcomes were analyzed using western blot and immunofluorescence methods. According to the findings, extended exposure to isoflurane anesthesia may lead to developmental neurotoxicity in vivo and in vitro. The anesthesia-induced neurotoxicity was concomitant with a reduction in LanCL1 expression. Moreover, the study revealed that overexpression of LanCL1 can mitigate the neurotoxic effects of isoflurane anesthesia, resulting in improved synaptic growth, less reactive oxygen species, enhanced cell viability and rescued memory deficits in the developing brain. In conclusion, prolonged anesthesia-induced LanCL1 deficiency could be responsible for neurotoxicity and subsequent cognitive impairments in the developing brain. Additional LanCL1 counteracts this neurotoxic effect and protects neurons from long-term isoflurane anesthesia.

Efficacy and safety of subcutaneous injection of botulinum toxin in the treatment of Chinese postherpetic neuralgia compared to analgesics: a systematic review of randomized controlled trials and meta-analysis

Objective

The purpose of this meta-analysis is to investigate the efficacy and safety of a subcutaneous injection of botulinum toxin in the treatment of postherpetic neuralgia (PHN) compared to analgesics.

Methods

We searched PubMed, Cochrane Library, Embase, Web of Science, Chinese National Knowledge Infrastructure (CNKI), and Wanfang for randomized controlled trials (RCTs) from inception to 10 September 2023. The primary clinical outcomes included visual analog scale (VAS) pain scores and clinical effective rates. The secondary clinical outcome included the adverse event rate during follow-up.

Results

A total of 14 studies with 1,358 participants were included in the meta-analysis. Among the included patients, 670 participants received botulinum toxin A injections and 688 participants received other medication treatments. The botulinum toxin-A (BTX-A) group exhibited lower pain scores [week 2: Mean difference (MD): -1.91, 95% confidence interval (CI): -2.63 to -1.20, and p < 0.00001; week 4: MD: -1.69, 95% CI: -2.69 to -0.68, and p < 0.00001; week 8: MD: -1.66, 95% CI: -2.20 to -1.12, and p < 0.00001; week 12:MD: -1.83, 95% CI: -2.70 to -0.96, and p < 0.00001; and week 24: MD: -1.07, 95% CI: -1.16 to -0.99, and p < 0.00001]. The effective rate was significantly higher in patients who received BTX-A for postherpetic neuralgia compared to those who received lidocaine or gabapentin (lidocaine: MD: -1.55, 95% CI: -2.84 to -0.27, and p = 0.02 and gabapentin: MD: -1.57, 95% CI: -2.12 to -1.02; and p < 0.00001). There was no difference in the incidence of adverse events between the treatment groups [odds ratio (OR): 1.25, 95% CI: 0.43 to 3.61, and p = 0.69].

Conclusion

Our meta-analysis showed that BTX-A has certain advantages in relieving postherpetic neuralgia compared to analgesics. In addition, BTX-A is safe for treating postherpetic neuralgia, with no notable side effects.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42021289813.

Mirogabalin as a Therapeutic Option for Neuropathic Pain Emerging Post-endodontic Treatment: A Two-Case Report

INTRODUCTION

Occlusal and percussion pain may manifest occasionally following endodontic treatment, influencing retreatment decisions. Two cases of periapical neuropathic pain, classified as post-traumatic trigeminal neuropathic pain according to the International Classification of Orofacial Pain, are presented. Although mirogabalin is effective in managing neuropathic pain, there is a lack of clinical reports on its use for occasional post-traumatic trigeminal neuropathic pain after endodontic treatment. These cases highlight clinical symptoms and successful treatment with mirogabalin for post-traumatic trigeminal neuropathic pain after endodontic treatment, providing clinicians a "take-away" lesson for improving patient condition.

METHODS

The patients, referred by their primary dentist due to postendodontic abnormal pain, found no relief with antibiotics or nonsteroidal anti-inflammatory drugs. Although no findings including swelling or periapical radiolucency were observed around the tooth, they experienced occlusal and percussion pain. Local anesthetic testing showed that the pain originated from the peripheral area around the tooth rather than from central sensitization. Dental radiography and cone-beam computed tomography revealed no abnormal findings. Root canal retreatment was performed by a specialist in endodontic treatment. Although endodontic retreatment drastically decreased visual analog scale pain score, pain persisted. Based on the International Classification of Orofacial Pain criteria, diseases other than post-traumatic trigeminal neuropathic pain were excluded. Mirogabalin (10 mg/d) was prescribed once daily before bedtime.

RESULTS

Visual analog scale scores gradually and drastically decreased 2 weeks after mirogabalin therapy. Several months later, no recurrence of postendodontic pain was observed after tapering off and discontinuing mirogabalin.

CONCLUSIONS

These findings suggest the possibility of a new treatment method for post-traumatic trigeminal neuropathic pain after endodontic treatment.

Strategies for measuring non-evoked pain in preclinical models of neuropathic pain: Systematic review

The development of new analgesics for neuropathic pain treatment is crucial. The failure of promising drugs in clinical trials may be related to the over-reliance on reflex-based responses (evoked pain) in preclinical drug testing, which may not fully represent clinical neuropathic pain, characterized by spontaneous non-evoked pain (NEP). Hence, strategies for assessing NEP in preclinical studies emerged. This systematic review identified 443 articles evaluating NEP in neuropathic pain models (mainly traumatic nerve injuries in male rodents). An exponential growth in NEP evaluation was observed, which was assessed using 48 different tests classified in 12 NEP-related outcomes: anxiety, exploration/locomotion, paw lifting, depression, conditioned place preference, gait, autotomy, wellbeing, facial grooming, cognitive impairment, facial pain expressions and vocalizations. Although most of these outcomes showed clear limitations, our analysis suggests that conditioning-associated outcomes, pain-related comorbidities, and gait evaluation may be the most effective strategies. Moreover, a minimal part of the studies evaluated standard analgesics. The greater emphasis on evaluating NEP aligning with clinical pain symptoms may enhance analgesic drug development, improving clinical translation.

Angiotensin II Type 2 Receptor Antibodies in Glomerular Diseases

We evaluated the concentration of AT2R antibodies in 136 patients with primary and secondary glomerular diseases: membranous nephropathy (n = 18), focal and segmental glomerulosclerosis (n = 25), systemic lupus erythematosus (n = 17), immunoglobulin A (IgA) nephropathy (n = 14), mesangial (non-IgA) proliferative nephropathy (n = 6), c-ANCA vasculitis (n = 40), perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCA) vasculitis (n = 16), and compared it with a healthy control group (22 patients). Serum creatinine levels, proteinuria, serum albumin, and total protein concentrations were prospectively recorded for 2 years. The mean levels of AT2R antibodies in the lupus nephropathy group were significantly higher compared to the control group, 64.12 ± 26.95 units/mL and 9.72 ± 11.88 units/mL, respectively. There was no association between this level and the clinical course of the disease. The AT2R levels in other kinds of glomerular disease were no different from the control group. We found significant correlations between AT1R and AT2R in patients with membranous nephropathy (r = 0.66), IgA nephropathy (r = 0.61), and c-ANCA vasculitis (r = 0.63). Levels of AT2R antibodies in systemic lupus erythematosus are higher compared to other types of glomerulonephritis, vasculitis, and a healthy control group. Levels of AT2R antibodies correlate with AT1R antibodies in the groups of patients with membranous nephropathy, IgA nephropathy, and c-ANCA vasculitis. These kinds of AT2R antibodies have a stimulative effect on AT2R, but we have not found the influence of these antibodies on the clinical course of glomerular diseases.