Several options effective for postherpetic neuralgia

ABSTRACT

BACKGROUND: Postherpetic neuralgia (PHN) is the most common complication of herpes zoster, especially in older patients, and can last weeks to years. This study evaluated the literature to determine the most effective treatments for PHN.

POPULATION STUDIED: Patients in the included studies were a mean age of 71 years (range, 16–90 years). Most of the patients had had PHN for more than 1 year.

STUDY DESIGN AND VALIDITY: This study was a well-done systematic review of English language, randomized controlled trials evaluating treatments for PHN with patient-relevant outcomes and evaluation periods of more than 24 hours. After a qualitative assessment of the 186 identified studies, 27 were included for methodologic review. Methodologic quality of the studies was rated independently by the authors using the 5-point Jadad scale, which is a well-evaluated validity checklist addressing randomization technique, allocation concealment, blinding, and accounting of dropouts. Most of the trials were found to be of good quality, receiving a Jadad score of 4. Trials scoring only 1 point were excluded with 2 exceptions: both were not double-blinded but were otherwise methodologically strong.

OUTCOMES MEASURED: Outcomes measured were PHN pain resolution, severity, and effect on quality of life.

RESULTS: The strongest evidence in this review supported the use of tricyclic antidepressants for the treatment of PHN, with 1 patient responding for every 2 to 3 who were treated (number needed to treat [NNT] = 2–3). Common side effects were dry mouth, drowsiness, and constipation. Amitriptyline was the best-studied antidepressant, at a dose of 75 mg nightly. Gabapentin 1200 mg 3 times daily was effective in a single, large placebo-controlled trial with an NNT of 3.2 for the outcome of moderate or better pain relief and 13.9 for the outcome of no pain during the 8th week of treatment. For every 2 patients treated with gabapentin, 1 had somnolence, dizziness, or ataxia. Controlled-release oxycodone 20 mg every 12 hours was effective in a crossover trial with an NNT of 2 for pain relief and common side effects of constipation, nausea, and sedation. Topical capsaicin 0.075% cream applied 4 times daily showed a trend toward effectiveness in a large trial and greater effectiveness in a smaller trial with an NNT of 2 for pain relief, although skin reaction was common and caused significant patient dropout from the study. The ability to blind these studies was difficult because of the stinging effect of the capsaicin. Intrathecal methylprednisolone plus lidocaine was highly effective for achieving good or excellent results (pain relief > 50%) in patients with longstanding PHN refractory to multiple conventional therapies, with an NNT of 2 and no reported adverse effects.