What are the treatment options for postherpetic neuralgia?

Treatment of Postherpetic Neuralgia

Start with gabapentin as first-line oral therapy (300 mg day 1,600 mg day 2,900 mg day 3, titrating to 1800-3600 mg/day in three divided doses) or topical lidocaine 5% patches for localized pain, particularly in elderly patients. 1, 2

First-Line Treatment Options

Oral Pharmacotherapy

• Gabapentin is the recommended first-line oral agent, with FDA approval for postherpetic neuralgia and demonstrated efficacy in reducing pain scores from 6.3 to 4.2 points (vs. 6.5 to 6.0 with placebo, p<0.001) 1, 3, 4
• Initiate gabapentin at 300 mg on day 1,600 mg on day 2, and 900 mg on day 3, then titrate in 600-1200 mg/day increments every 3-7 days to reach 1800-3600 mg/day in three divided doses 1
• No additional benefit occurs above 1800 mg/day, so avoid unnecessarily high doses that increase side effects without improving pain control 1
• In elderly patients, start with 100-200 mg/day and titrate more gradually to minimize somnolence, dizziness, and mental clouding 2

Topical Therapy (Preferred for Elderly/Localized Pain)

• Topical lidocaine 5% patches provide excellent efficacy (NNT = 2) with minimal systemic absorption, making them ideal for elderly patients or those with comorbidities 1, 2
• Apply patches for 12-24 hours on affected areas, delivering medication gradually with negligible systemic effects 1
• Capsaicin 8% patches offer another topical option, providing pain relief for at least 12 weeks 1, 2
• To minimize capsaicin-induced erythema and pain, pretreat with 4% lidocaine for 60 minutes before capsaicin application 1, 2

Tricyclic Antidepressants

• Nortriptyline has excellent efficacy (NNT = 2.64) and is preferred over amitriptyline due to better tolerability with equivalent analgesic benefit 1, 5, 6
• Start nortriptyline at 10-25 mg at bedtime, increasing every 3-7 days to a target dose of 25-100 mg at bedtime 1, 5
• In elderly patients, begin with 10 mg and titrate more slowly to minimize anticholinergic side effects 5
• Continue treatment indefinitely until pain resolves, as postherpetic neuralgia may persist for months to years 5

Second-Line Treatment Options

When First-Line Agents Fail

• Pregabalin is appropriate if gabapentin provides inadequate response, with an NNT of 4.93 and FDA approval for postherpetic neuralgia 1, 7
• Dose pregabalin at 150-600 mg/day in two divided doses, with demonstrated efficacy across this range 1, 7
• Pregabalin showed statistically significant improvement in pain scores and increased the proportion of patients achieving ≥50% pain reduction from baseline 7
• Tramadol demonstrates efficacy with an NNT of 4.76 and can be considered as an alternative second-line agent 1

Opioid Therapy (Use with Caution)

• Opioids (oxycodone, extended-release morphine, methadone) show excellent efficacy (NNT = 2.67) but should NOT be used as first-line agents due to risks of pronociception, cognitive impairment, respiratory depression, endocrine/immunological changes, and potential for misuse and addiction 1, 2
• Reserve opioids for patients who have failed multiple first- and second-line therapies 1, 2
• Controlled-release oxycodone has been shown in randomized trials to provide superior pain relief compared to placebo 6

Combination Therapy

• When single agents provide inadequate relief, combine morphine with gabapentin for additive effects while allowing lower doses of each medication 1, 2
• This approach reduces individual drug-related side effects while maintaining or improving pain control 1

Non-Pharmacological Approaches

• Cognitive behavioral therapy (CBT), hypnosis, and physical/occupational therapy may provide additional benefit for pain management 1
• These modalities are particularly valuable as adjuncts to pharmacotherapy rather than standalone treatments 1

Critical Pitfalls to Avoid

• Never use lamotrigine for postherpetic neuralgia—it lacks convincing efficacy evidence and carries risk of serious skin rash 1, 2
• Always adjust doses based on renal function in elderly patients to prevent drug accumulation and toxicity, particularly with gabapentin and pregabalin 2
• Monitor closely for neurological side effects (somnolence, dizziness, confusion) that are especially problematic in older adults receiving gabapentinoids 1, 2
• Avoid unnecessarily high gabapentin doses above 1800 mg/day, as they provide no additional benefit but increase adverse effects 1

Treatment Algorithm

1. Start with topical lidocaine 5% patches if pain is well-localized and patient is elderly or has multiple comorbidities 1, 2
2. If topical therapy insufficient or pain is widespread, initiate gabapentin using the rapid titration schedule (300/600/900 mg over 3 days, then increase to 1800-3600 mg/day) 1, 3
3. Alternatively, start nortriptyline 10-25 mg at bedtime if patient tolerates anticholinergic effects, titrating to 25-100 mg 1, 5
4. If first-line oral agent fails, switch to pregabalin 150-600 mg/day in divided doses 1, 7
5. Consider combination therapy (gabapentin + morphine) if monotherapy inadequate 1, 2
6. Reserve opioids for refractory cases after exhausting other options 1, 2
7. Reassess periodically, as postherpetic neuralgia may improve over time, allowing dose reduction or discontinuation 1