OnabotulinumtoxinA Appears to Improve Pain and Sleep in Patients with Chronic Postherpetic Neuralgia

EBM Focus - Volume 8, Issue 14

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Reference: Clin J Pain 2013 Jan 30 early online, (level 2 [mid-level] evidence)

About 10% of patients develop severe chronic neuropathic pain following acute herpes zoster, with the frequency being higher in older patients. Postherpetic neuralgia can be difficult to manage. Various treatments that have been used include oral analgesics, tricyclic antidepressants, anticonvulsants, topical lidocaine and topical capsaicin. A recent small randomized trial evaluated the efficacy of onabotulinumtoxinA injections for pain relief in chronic postherpetic neuralgia.

Thirty adults with postherpetic neuralgia for at least 3 months (mean duration 104 days) were randomized to onabotulinumtoxinA (100 units in 4 mL normal saline) vs. placebo in a single treatment of 40 subcutaneous injections. The injections were made with 30-gauge needles in a chess board pattern over the affected areas designated by the patients (thoracic dermatomes in 25 patients, brachial plexus in 4 patient, and sciatic nerve in 1 patient). The minimal distance between injection sites was 1 cm. Pain was rated on 0-10 visual analog scale and sleep quality was rated on 0-15 scale by 5-item questionnaire (higher scores indicating worse outcomes).

At 4 weeks, pain reduction of at least 50% was reported in 87% with onabotulinumtoxinA compared to 0% with placebo (p < 0.001, NNT 2). The median time to 50% pain reduction was 7.4 days, and pain reduction was maintained for median 16 weeks. The mean sleep scores at 4 weeks were 4.1 with onabotulinumtoxinA vs. 8.5 with placebo (p < 0.001), and this difference was maintained at 16 weeks. No adverse events were reported.

For more information, see the Postherpetic neuralgia topic in DynaMed.