Review of current guidelines on the care of postherpetic neuralgia

Safety and efficacy of once-daily gastroretentive gabapentin in patients with postherpetic neuralgia aged 75 years and over

Background

Treatment of postherpetic neuralgia (PHN) is more complicated in elderly patients, and multiple daily dosing, complex titration, and high incidences of adverse events can be limiting for many pharmacological treatment options.

Objective

The aim of this study was to determine whether the efficacy and tolerability of once-daily gastroretentive gabapentin (G-GR) is similar between elderly patients (≥75 years) and younger patients (<75 years).

Methods

Data from two phase III, placebo-controlled studies of 1,800 mg G-GR once daily with dinner in patients with PHN were integrated and analyzed by age subgroups (<75 years, n = 527; ≥75 years, n = 192). Efficacy assessments at endpoint (week 10) included baseline-adjusted change in average daily pain (ADP) and average daily sleep interference (SIS) scores, the proportion of responders (≥30 % pain reduction), and the proportion of patients feeling “Much” or “Very Much” improved on the Patient Global Impression of Change (PGIC).

Results

Compared with placebo, patients in both age subgroups treated with G-GR (placebo/G-GR) had greater reductions in mean ADP (≥75: −21.9/−34.2 %, p = 0.0348; <75: −29.9/−38.3 %, p = 0.0079) and SIS (≥75: −1.3/−2.4, p = 0.0017; <75: −1.8/−2.7, p < 0.0001), more patients were responders (≥75: 30.4/52.0 %, p = 0.0025; <75: 45.0/54.7 %, p = 0.0265), and more felt “Much” or “Very Much” improved on the PGIC (≥75: 20.7/35.0 %, p = 0.0272; <75: 33.6/44.9 %, p = 0.0077). The most common (placebo/G-GR) adverse events (AEs) were dizziness (≥75: 3.3/12.0 %; <75: 1.8/10.4 %), nausea (≥75: 1.0/5.4 %; <75: 2.9/4.2 %), and somnolence (≥75: 0/5.0 %; <75: 3.7/4.2 %). For all patients, AEs rapidly decreased to low steady levels after 4–5 weeks of treatment. The incidence of serious AEs was low and they were reported more frequently in the placebo than in the G-GR group.

Conclusions

Therapy with once-daily G-GR was as effective for treating pain associated with PHN in elderly patients as it was in younger patients. G-GR was well tolerated, and the incidence of the most common AEs did not appear to be age related.

Vaccination against and treatment of acute herpes zoster for prevention of post-herpetic neuralgia

Zostavax (zoster vaccine) is a 1-dose, high-potency, live, attenuated varicella zoster virus (VZV) vaccine that boosts VZV-specific cell-mediated immunity (CMI), and this is its presumed mechanism of action. Other strategies focus on preventing the major complication of HZ, post-herpetic neuralgia (PHN). Evidence that the vaccine is effective in older patients comes from the pivotal Shingles Prevention Study. That study demonstrated that HZ vaccine significantly reduced morbidity due to HZ and PHN in older patients. However, the duration of efficacy beyond 5 years after vaccination remains unclear. The Long-Term Persistence Substudy, currently under analysis, may provide additional data on the duration of efficacy for zoster vaccine. This review discusses vaccination against HZ, and further reviews recent pharmacotherapy for prevention of PHN.

Capsaicin-based therapies for pain control

The TRPV1 receptor is known to play a role in nociceptive transmission in multiple organ systems, usually in response to the pain of inflammation. TRPV1 antagonism has so far shown limited benefit in antinociception. Capsaicin, a TRPV1 agonist, has been shown to induce a refractory period in the nerve terminal expressing TRPV1 and even, in sufficient dosing, to create long-term nerve terminal defunctionalization. This has led to research into topical capsaicin as a treatment for multiple painful conditions. The majority of work has focused on musculoskeletal pain and neuropathic pain and has revealed that although low-dose topical capsaicin has limited effectiveness as an analgesic, high-dose capsaicin, when tolerated, has the potential for long-term analgesia in certain types of neuropathic pain.

Bee venom treatment for refractory postherpetic neuralgia: a case report

OBJECTIVE

Bee venom has been reported to have antinociceptive and anti-inflammatory effects in experimental studies. However, questions still remain regarding the clinical use of bee venom. This report describes the successful outcome of bee venom treatment for refractory postherpetic neuralgia.

PATIENT

A 72-year-old Korean man had severe pain and hypersensitivity in the region where he had developed a herpes zoster rash 2 years earlier. He was treated with antivirals, painkillers, steroids, and analgesic patches, all to no effect.

INTERVENTION

The patient visited the East-West Pain Clinic, Kyung Hee University Medical Center, to receive collaborative treatment. After being evaluated for bee venom compatibility, he was treated with bee venom injections. A 1:30,000 diluted solution of bee venom was injected subcutaneously along the margins of the rash once per week for 4 weeks.

RESULTS

Pain levels were evaluated before every treatment, and by his fifth visit, his pain had decreased from 8 to 2 on a 10-point numerical rating scale. He experienced no adverse effects, and this improvement was maintained at the 3-month, 6-month, and 1-year phone follow-up evaluations.

CONCLUSION

Bee venom treatment demonstrates the potential to become an effective treatment for postherpetic neuralgia. Further large-sample clinical trials should be conducted to evaluate the overall safety and efficacy of this treatment.

Options for treating postherpetic neuralgia in the medically complicated patient

Patients with postherpetic neuralgia (PHN) are often of advanced age or immunocompromised and likely to have ≥1 comorbid medical condition for which they receive ≥1 medication (polypharmacy). Comorbidities affecting renal or hepatic function can alter pharmacokinetics, thereby impacting the efficacy or tolerability of PHN analgesic therapies. Cardiovascular, cerebrovascular, or psychiatric comorbidities may increase patient vulnerability to potential adverse events associated with some PHN analgesic therapies. Because PHN is a localized condition, localized therapy with a topical analgesic (lidocaine patch 5% and capsaicin 8% patch or cream) may provide adequate efficacy while mitigating the risk of systemic adverse events compared with oral analgesics (eg, tricyclic antidepressants, anticonvulsants, opioids). However, combined therapy with a topical and an oral analgesic or with >1 oral analgesic may be needed for optimal pain management in some patients. This review summarizes how comorbidities and concomitant medications should be taken into account when selecting among available pharmacotherapies for PHN and provides recommendations for the selection of therapies that will provide analgesia while minimizing the risk of adverse events.

Cranial neuralgias

This article describes the clinical findings of cranial neuralgias, such as trigeminal neuralgia, glossopharyngeal neuralgia, nervus intermedius neuralgia, and others, and postherpetic neuralgia. Pathophysiology of these neuralgias, diagnostic methods, and treatment are also discussed. This information will enable the dentist to diagnose patients who have these rare conditions.

Clinical practice guidelines and practice parameters for the child neurologist

Guidance about how to practice child neurology has been around for decades. Recently, however, clinical practice guidelines, practice parameters, and standardized clinical assessment and management plans are gaining increasing attention. This overview, written for child neurologists, addresses such issues as the following: what are clinical practice guidelines, why are they needed, how are they created, how should they be created, how well are they accepted and adhered to, what influences acceptance and adherence, do guidelines improve care, do they reduce costs, will they be viewed by courts as the standard of care, how can they be updated and improved, and are there better alternatives?

Implications and mechanism of action of gabapentin in neuropathic pain

Gabapentin is an anti-epileptic agent but now it is also recommended as first line agent in neuropathic pain, particularly in diabetic neuropathy and post herpetic neuralgia. α2δ-1, an auxillary subunit of voltage gated calcium channels, has been documented as its main target and its specific binding to this subunit is described to produce different actions responsible for pain attenuation. The binding to α2δ-1 subunits inhibits nerve injury-induced trafficking of α1 pore forming units of calcium channels (particularly N-type) from cytoplasm to plasma membrane (membrane trafficking) of pre-synaptic terminals of dorsal root ganglion (DRG) neurons and dorsal horn neurons. Furthermore, the axoplasmic transport of α2δ-1 subunits from DRG to dorsal horns neurons in the form of anterograde trafficking is also inhibited in response to gabapentin administration. Gabapentin has also been shown to induce modulate other targets including transient receptor potential channels, NMDA receptors, protein kinase C and inflammatory cytokines. It may also act on supra-spinal region to stimulate noradrenaline mediated descending inhibition, which contributes to its anti-hypersensitivity action in neuropathic pain.

Topical analgesics in the management of acute and chronic pain

Oral analgesics are commonly prescribed for the treatment of acute and chronic pain, but these agents often produce adverse systemic effects, which sometimes are severe. Topical analgesics offer the potential to provide the same analgesic relief provided by oral analgesics but with minimal adverse systemic effects. This article describes the results of a systematic review of the efficacy of topical analgesics in the management of acute and chronic pain conditions. A literature search of MEDLINE/PubMed was conducted using the keywords topical analgesic AND chronic pain OR acute pain OR neuropathic pain and focused only on individual clinical trials published in English-language journals. The search identified 92 articles, of which 65 were eligible for inclusion in the review. The most commonly studied topical analgesics were nonsteroidal anti-inflammatory drugs (n=27), followed by lidocaine (n=9), capsaicin (n=6), amitriptyline (n=5), glyceryl trinitrate (n=3), opioids (n=2), menthol (n=2), pimecrolimus (n=2), and phenytoin (n=2). The most common indications were acute soft tissue injuries (n=18), followed by neuropathic pain (n=17), experimental pain (n=6), osteoarthritis and other chronic joint-related conditions (n=5), skin or leg ulcers (n=5), and chronic knee pain (n=2). Strong evidence was identified for the use of topical diclofenac and topical ibuprofen in the treatment of acute soft tissue injuries or chronic joint-related conditions, such as osteoarthritis. Evidence also supports the use of topical lidocaine in the treatment of postherpetic neuralgia and diabetic neuropathy. Currently, limited evidence is available to support the use of other topical analgesics in acute and chronic pain.

Survey on the treatment of postherpetic neuralgia in Korea; multicenter study of 1,414 patients

Background

Postherpetic neuralgia (PHN) is a serious complication resulting from herpes zoster infections, and it can impair the quality of life. In order to relieve pain from PHN, various treatments, including pharmacological and interventional methods have been used. However, little information on the recommendations for the interventional treatment of PHN, along with a lack of nation-wide surveys on the current status of PHN treatment exists. This multicenter study is the first survey on the treatment status of PHN in Korea.

Methods

Retrospective chart reviews were conducted on the entire patients who visited the pain clinics of 11 teaching hospitals from January to December of 2011. Co-morbid disease, affected site of PHN, routes to pain clinic visits, parenteral/topical medications for treatment, drugs used for nerve block, types and frequency of nerve blocks were investigated.

Results

A total of 1,414 patients' medical records were reviewed. The most commonly affected site was the thoracic area. The anticonvulsants and interlaminar epidural blocks were the most frequently used pharmacological and interventional methods for PHN treatment. For the interval of epidural block, intervals of 5 or more-weeks were the most popular. The proportion of PHN patients who get information from the mass media or the internet was only 0.8%.The incidence of suspected zoster sine herpete was only 0.1%.

Conclusions

The treatment methods for PHN vary among hospitals. The establishment of treatment recommendation for PHN treatment is necessary. In addition, public relations activities are required in order to inform the patients of PHN treatments by pain clinicians.

Influence of anatomic location of lidocaine patch 5% on effectiveness and tolerability for postherpetic neuralgia

PURPOSE

Lidocaine patch 5% is recommended as a first-line therapy for postherpetic neuralgia pain in neuropathic pain guidelines. Postherpetic neuralgia can occur anywhere on the body but often follows acute herpes zoster occurring in trigeminal and brachial plexus dermatomes. An analysis was conducted to determine whether the anatomic location of lidocaine patch 5% is associated with variations in effectiveness or tolerability in patients with postherpetic neuralgia.

METHODS

This was a post hoc analysis by anatomic site of patch placement (head [including neck], trunk [chest, abdomen, back, hips], and extremities [arm, leg]) of a 4-week, multicenter, open-label study that enrolled patients with persistent pain following herpes zoster infection. Effectiveness was measured by Brief Pain Inventory (BPI) average pain intensity (0 [no pain] to 10 [worst imaginable pain]) and the BPI subscale for pain relief (0% [no relief] to 100% [complete relief]). Tolerability was assessed on the basis of patient-reported adverse events.

RESULTS

Of 332 enrolled patients (59.6% women [n = 198]; 92.5% white [n = 307]; mean [standard deviation] age, 71.2 [13.9] years), those (n = 203) who applied lidocaine patch 5% to a single anatomic site only and had baseline and postbaseline pain score data were analyzed (trunk, n = 130; head, n = 41; extremities, n = 32). The frequency of adverse events differed significantly by anatomic location, with significantly more adverse events reported with patch placement on the head versus the extremities (P = 0.006) or trunk (P = 0.02). BPI average pain improved significantly from baseline in each of the three anatomic areas (mean score decrease, 1.50-2.04; P ≤ 0.002), with no significant difference in effectiveness by patch location.

CONCLUSION

Lidocaine 5% patch was effective and generally well tolerated for each anatomic area evaluated, although application to the head was tolerated less well compared with the trunk and extremities.

Real-world treatment of post-herpetic neuralgia with gabapentin or pregabalin

BACKGROUND AND OBJECTIVES

There are limited data examining the real-world use of gabapentin and pregabalin for the treatment of post-herpetic neuralgia (PHN). This study examines dosing patterns, therapy outcomes, healthcare utilization and costs of patients with PHN who initiate treatment with gabapentin or pregabalin.

METHODS

This was a retrospective administrative claims data analysis from July 2005 to February 2010. Patients with PHN initiating gabapentin or pregabalin (index therapy) from January 2006 to February 2009 were identified and were observed for 12 months after index therapy initiation. Outcomes were mean daily dosages of the index therapy, attainment of minimally effective dosages of gabapentin (≥ 1,800 mg/day) or pregabalin (≥ 150 and ≥ 300 mg/day) persistence, discontinuation, index therapy switching, addition of neuropathic pain medications to index therapy, and healthcare resource use and costs.

RESULTS

1,645 patients were identified. The mean daily dosage was 826 mg for gabapentin and 187 mg for pregabalin. Only 52.6 % of patients initiating gabapentin and 56.9 % initiating pregabalin obtained a refill during the post-index period. Approximately 14 % of patients treated with gabapentin reached the target dosage (1,800 mg/day). For pregabalin, 87 % reached ≥ 150 mg/day and 27 % reached ≥ 300 mg/day. On average, patients took 10 weeks to reach 1,800 mg/day gabapentin, and 5.0 and 9.2 weeks to reach ≥ 150 mg/day and ≥ 300 mg/day pregabalin, respectively. Approximately one-third of patients in both index therapy cohorts added a pain medication; more than half added opioids. The percentage of patients switching from either drug (57 %) or adding a therapy (34 %) were similar between index therapy cohorts; opioids were the most common therapy patients switched to or added.

CONCLUSION

It appears that gabapentin and pregabalin are not used effectively to treat PHN. Suboptimal dosing and discontinuation may be associated with supplementary use of other analgesics, especially opioids.

Diagnosing and managing postherpetic neuralgia

Postherpetic neuralgia (PHN) represents a potentially debilitating and often undertreated form of neuropathic pain that disproportionately affects vulnerable populations, including the elderly and the immunocompromised. Varicella zoster infection is almost universally prevalent, making prevention of acute herpes zoster (AHZ) infection and prompt diagnosis and aggressive management of PHN of critical importance. Despite the recent development of a herpes zoster vaccine, prevention of AHZ is not yet widespread or discussed in PHN treatment guidelines. Diagnosis of PHN requires consideration of recognized PHN signs and known risk factors, including advanced age, severe prodromal pain, severe rash, and AHZ location on the trigeminal dermatomes or brachial plexus. PHN pain is typically localized, unilateral and chronic, but may be constant, intermittent, spontaneous and/or evoked. PHN is likely to interfere with sleep and daily activities. First-line therapies for PHN include tricyclic antidepressants, gabapentin and pregabalin, and the lidocaine 5 % patch. Second-line therapies include strong and weak opioids and topical capsaicin cream or 8 % patch. Tricyclic antidepressants, gabapentinoids and strong opioids are effective but are also associated with systemic adverse events that may limit their use in many patients, most notably those with significant medical comorbidities or advanced age. Of the topical therapies, the topical lidocaine 5 % patch has proven more effective than capsaicin cream or 8 % patch and has a more rapid onset of action than the other first-line therapies or capsaicin. Given the low systemic drug exposure, adverse events with topical therapies are generally limited to application-site reactions, which are typically mild and transient with lidocaine 5 % patch, but may involve treatment-limiting discomfort with capsaicin cream or 8 % patch. Based on available clinical data, clinicians should consider administering the herpes zoster vaccine to all patients aged 60 years and older. Clinicians treating patients with PHN may consider a trial of lidocaine 5 % patch monotherapy before resorting to a systemic therapy, or alternatively, may consider administering the lidocaine 5 % patch in combination with a tricyclic antidepressant or a gabapentinoid to provide more rapid analgesic response and lower the dose requirement of systemic therapies.

Varicella zoster virus-induced pain and post-herpetic neuralgia in the human host and in rodent animal models

Pain and post-herpetic neuralgia (PHN) are common and highly distressing complications of herpes zoster that remain a significant public health concern and in need of improved therapies. Zoster results from reactivation of the herpesvirus varicella zoster virus (VZV) from a neuronal latent state established at the primary infection (varicella). PHN occurs in some one fifth to one third of zoster cases with severity, incidence, and duration of pain increasing with rising patient age. While VZV reactivation and the ensuing ganglionic damage trigger the pain response, the mechanisms underlying protracted PHN are not understood, and the lack of an animal model of herpes zoster (reactivation) makes this issue more challenging. A recent preclinical rodent model has developed that opens up the potential to allow the exploration of the underlying mechanisms and treatments for VZV-induced pain. Rats inoculated with live cell-associated human VZV into the hind paw reliably demonstrate thermal hyperalgesia and mechanical allodynia for extended periods and then spontaneously recover. Dorsal root ganglia express a limited VZV gene subset, including the IE62 regulatory protein, and upregulate expression of markers suggesting a neuropathic pain state. The model has been used to investigate treatment modalities and aspects of pain signaling and is under investigation by the authors to delineate VZV genetics involved in the induction of pain. This article compares human zoster-associated pain and PHN to the pain indicators in the rat and poses important questions that, if answered, could be the basis for new treatments.