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Emerging Treatments for Postherpetic Neuralgia

A brief review of pharmacological and non-pharmacological therapies showing promising results for patients with shingles.

A PPM Brief

Postherpetic neuralgia (PHN) is a sensory nervous system, injury-based neuropathic pain, caused by the herpes zoster virus. A complication of Shingles, PHN causes a persistent burning and paroxysmal stimulation pain that may last several months to several years, commonly occurring in the chest and back, but the pain may also affect the whole body. PHN is most frequently accompanied by severe pain, but the underlying mechanism of this complication remains misunderstood among the literature.

The pathogenesis of PHN has yet to be fully clarified, but most studies suggest that the herpes zoster virus located in the dorsal root ganglion is reactivated in persons age 60 or older, or in individuals with low immunity, thereby leading to the degeneration of the spinal nerve sensory system and increased neuropathic pain.1

Many promising therapies, both pharmacological and non-pharmacological, or a combination of the two, have shown positive results in recent studies, as highlighted below.

Gabapentin

One review2 of the literature found gabapentin to be a safe and effective treatment for PHN. Collecting data from 11 randomized controlled trials involving 2,376 subjects, gabapentin groups reported significantly reduced pain intensity [mean difference = -0.91, 95% CI -1.32 to -0.51, P < 0.00001] compared with placebo groups. Those treated with gabapentin also experienced significantly improved sleep quality [standardized mean difference = -0.44, 95% CI -0.66 to -0.23, P < 0.0001], but they were also more likely to experience incidence of adverse events, such as somnolence, dizziness, and peripheral edema.

Scrambler Therapy

A smaller study of 10 patients treated refractory PHN using scrambler therapy, a neurocutaneous stimulation device that delivers "nonpain" information using surface electrodes.3 The therapy was administered via 30-minute sessions daily for 10 days, with pain levels recorded pre and post-treatment. The sessions resulted, in average, in pain scores diminishing from 7.64 ± 1.46 baseline to 0.42 ± 0.89 at 1 month, a 95% reduction, with continued relief at Month 2 and Month 3 followup; patients achieved maximum pain relief with less than five treatments.

Ozone Autohemotherapy

Ozone autohemotherapy, an alternative medicine that aims to increase the amount of oxygen in the body through the introduction of ozone, combined with pharmacological therapy in PHN made for a good combination in one study4 of 98 patients randomly divided into a pharmacological therapy group and ozone autohemotherapy group (49 in each group).

PHN patients in the pharmacological therapy group were administered pharmacological therapy (diclofenac 75 mg/day, pregabalin 300 mg/day, and cobamamide 1 mg/day) for 2 weeks, whereas PHN patients in the ozone autohemotherapy group were given ozone autohemotherapy (200 mL blood from patients; the concentration of medical ozone was set as 30 μg/mL using an ozone medical apparatus, 40 mL medical ozone was incubated in 200 mL autologous blood for 3-5 minutes) combined with pharmacological therapy for 2 weeks.

Source: 123RFShinges, or postherpetic neuralgia, often affects older patients.

Researchers used the Visual Analog Scale (VAS), McGill Pain Questionnaire (MPQ), the Patients' Global Impression of Change (PGIC) scale, and the World Health Organization Quality of Life (WHOQOL-BREF) to evaluate patient responses. Outcomes were taken pre-therapy and at Week 1, Week 4, and 3 Months post-treatment.

Forty-five patients in the pharmacological therapy group and 47 patients in the ozone autohemotherapy group completed the study. Compared to baseline, the two groups showed significant improvements in VAS, MPQ, PGIC, and WHOQOL-BREF scores after therapy (p < 0.05). Moreover, compared with the scores of the pharmacological therapy group, the ozone autohemotherapy group's scores were significantly improved in the VAS, MPQ, PGIC, and WHOQOL-BREF as well as the 50% VAS reduction of the initial value after therapy (p < 0.05).

Neuromodulation

Both spinal cord stimulation (SCS) and peripheral nerve stimulation (PNS) are considered mostly experimental and still rarely performed in patients with PHN.5 However, some reports show promising outcomes for patients. A review5 of 20 original reports involved 309 patients with PHN treated with SCS. A total of 16 of the reports had a permanent SCS implantation with a total of 255 patients, where 120 patients had long-term pain relief.

There were six reports of subcutaneous PNS (in the thoracic area) for PHN, where researchers concluded that subcutaneous PNS seems to be a promising intervention in the treatment of PHN. For example, in the researchers’ practice at the Mayo Clinic in Jacksonville, FL, two patients underwent subcutaneous PNS for PHN with good pain relief for 10 months and 2.5 years, respectively.

Currently, clinical therapy of the disease consists of comprehensive measures to compensate for the shortcomings of a single treatment, as the available therapies for PHN are still not ideal.4 It is hoped that these promising developments bring about further research on their safety and efficacy.

Last updated on: November 12, 2018
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Non-pharmacologic Treatment of Shingles
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