What is the recommended treatment for a patient with post herpetic neuralgia?

Treatment of Post-Herpetic 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 use 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, initiated at 300 mg on day 1,600 mg on day 2 (divided twice daily), and 900 mg on day 3 (divided three times daily), with subsequent titration to 1800 mg/day (600 mg three times daily) for pain relief. 2
• Efficacy is demonstrated across the dose range of 1800-3600 mg/day, but no additional benefit is shown above 1800 mg/day, so higher doses are unnecessary. 1, 2
• In elderly patients or those with renal impairment, start with 100-200 mg/day and titrate more gradually, adjusting doses based on creatinine clearance. 1, 2

Topical Therapy (Preferred for Elderly/Localized Pain)

• Lidocaine 5% patches provide excellent efficacy (NNT = 2) with minimal systemic absorption, making them ideal for elderly patients or those with comorbidities, worn for 12-24 hours on affected areas. 1, 3
• Capsaicin 8% patches can provide pain relief for at least 12 weeks; apply 4% lidocaine for 60 minutes before capsaicin application to mitigate erythema and pain. 1, 3

Tricyclic Antidepressants (Alternative First-Line)

• Nortriptyline is preferred over amitriptyline with excellent efficacy (NNT = 2.64) and better tolerability while providing equivalent analgesic benefit. 1, 4, 5
• Start at 10-25 mg at bedtime, increase every 3-7 days as tolerated to a target dose of 25-100 mg at bedtime. 4
• In elderly patients (≥65 years), start with 10 mg and titrate more slowly to minimize anticholinergic side effects. 1, 4

Second-Line Treatment Options

When Gabapentin Fails or Is Insufficient

• Pregabalin is the alternative gabapentinoid if gabapentin provides inadequate response, with NNT of 4.93 and effective doses of 150-600 mg/day in two divided doses. 1
• Start at 25-50 mg/day and titrate to the effective dose range, monitoring for somnolence, dizziness, and mental clouding, especially in older patients. 1

Opioid Therapy (Use With Caution)

• Opioids (oxycodone, extended-release morphine, methadone) show excellent efficacy (NNT = 2.67) but should NOT be first-line agents due to risks of pronociception, cognitive impairment, respiratory depression, endocrine/immunological changes, and potential for misuse and addiction. 1, 3, 6
• Tramadol shows efficacy with NNT of 4.76 and may be considered as a safer opioid alternative. 1
• Combination therapy (morphine with gabapentin) may be more effective when single agents provide inadequate relief, allowing lower doses of each medication while providing additive effects. 1, 3

Treatment Duration and Monitoring

• Continue treatment indefinitely until pain resolves, as post-herpetic neuralgia may persist for months to years. 4
• Conduct periodic reassessment of continued therapy, as the condition may improve over time. 1
• The probability of pain relief correlates with early treatment initiation. 4

Common Pitfalls and Contraindications

Medications to Avoid

• Lamotrigine is NOT recommended for PHN due to lack of convincing evidence of efficacy and risk of lamotrigine-associated rash. 1, 3
• Corticosteroids provide no benefit for established postherpetic neuralgia and expose patients to unnecessary adverse effects including hyperglycemia, osteoporosis, hypertension, and immunosuppression. 1
• Selective serotonin reuptake inhibitors (SSRIs) show little effectiveness in neuropathic pain. 7

Monitoring Considerations

• Monitor closely for neurological side effects (somnolence, dizziness, confusion, mental clouding) with gabapentinoids, particularly problematic in older adults. 1, 3
• Always adjust doses based on renal function in elderly patients to prevent toxicity, as gabapentin requires dose reduction when creatinine clearance is <60 mL/min. 2
• The maximum time between gabapentin doses should not exceed 12 hours. 2

Non-Pharmacological Approaches

• Cognitive behavioral therapy (CBT), hypnosis, and physical/occupational therapy may be beneficial adjuncts. 1, 3
• Interventional treatments (botulinum toxin A injection, transcutaneous electrical nerve stimulation, stellate ganglion block, pulsed radiofrequency) should be considered for refractory cases not responding to pharmacotherapy. 8