Clinical Inquiries

What measures relieve postherpetic neuralgia?

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Tricyclic antidepressants, gabapentin, and pregabalin effectively reduce pain (strength of recommendation [SOR]: A, at least 2 good-quality randomized controlled trials [RCTs] and/or meta-analyses). Opioids have demonstrated pain relief in 3 RCTs (SOR: A, consistent RCTs). Capsaicin and the lidocaine 5% patch relieve pain and decrease allodynia (SOR: B, recommendations from meta-analyses and lower-quality RCTs).

Evidence summary

Postherpetic neuralgia (PHN) is defined as pain lasting 1 to 3 months after resolution of acute herpes zoster (shingles) rash. It occurs in approximately 10% to 15% of patients and can cause significant morbidity.

Tricyclic antidepressants provide effective pain relief

Five systematic reviews have concluded that tricyclic antidepressants (TCAs) are effective treatments for PHN.1-5 Amitriptyline, the best studied TCA, provides at least moderate pain relief in two-thirds of patients with a pooled number needed to treat (NNT) for TCAs of 2.64 (95% confidence interval [CI], 2.1-3.54)5 (TABLE).

Selective serotonin reuptake inhibitors—including fluoxetine, paroxetine, citalopram, and sertraline—have been studied in a variety of neuropathic pain syndromes, but not for treating PHN.1

What’s the NNT for drugs used to treat postherpetic neuralgia?

Tricyclic antidepressants5AmitriptylineUp to 150 mg/d (mean 120 mg/d)2.64Sedation, dry mouth, blurred vision, constipation, urinary retention
NortriptylineUp to 150 mg/d (mean 89 mg/d)
DesipramineUp to 150 mg/d (mean 65-73 mg/d)
Anticonvulsants3,5Gabapentin1800-3600 mg/d2.8-5.3Somnolence, dizziness, edema, dry mouth
Pregabalin150-600 mg/d4.93
Opioids5OxycodoneVariable2.67Constipation, nausea, vomiting, sedation, dizziness, dependence
Long-acting morphine/methadone15-225 mg/d (morphine) (mean 91 mg/d for morphine, 15 mg/d for methadone)2.67
Tramadol100-400 mg/d (mean 275 mg/d)4.76Dependence
Topicals5Capsaicin 0.075% creamApplied 3-4 times per day3.26Burning skin
Lidocaine 5% extended release patchMax 3 patches per day2.0Mild skin reaction
NNT, number needed to treat.

Anticonvulsants help, too

Five systematic reviews found gabapentin to be effective, with a range of NNT from 2.8 to 5.3 for as much as 50% pain reduction based on the visual analog score (VAS).2-6 Pregabalin is also effective, with an NNT of 4.93 (95% CI, 3.34-6.07) for up to 50% pain reduction.7,8 Limited data are available concerning the effectiveness of valproate.5

A look at the role of narcotics

Four systematic reviews found that controlled-release oxycodone reduced pain by 50%, based on the VAS.2-5 Another systematic review reported only limited evidence of effectiveness.6 In pooled results from systematic reviews, opioids decreased pain by 50% on the VAS (NNT=2.67; 95% CI, 2.10-3.77).6


Evidence-based answers from the Family Physicians Inquiries Network

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