What are the management options for post herpetic neuralgia?

Management 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 divided doses), or use topical lidocaine 5% patches for localized pain, particularly in elderly patients. 1, 2

First-Line Treatment Options

Topical Therapies (Preferred for Elderly or Localized Pain)

• 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 over hours with negligible systemic effects. 1
• Capsaicin 8% patches offer an alternative non-sedating option, providing pain relief for at least 12 weeks. 1
• To minimize capsaicin-related erythema and pain, pre-treat with 4% lidocaine for 60 minutes before capsaicin application. 1

Oral Pharmacotherapy

Gabapentin (First-Line Oral Agent)

• The American College of Physicians recommends gabapentin as first-line oral treatment, with FDA approval for postherpetic neuralgia. 1, 3
• Dosing protocol: Start 300 mg on day 1,600 mg on day 2,900 mg on day 3, then titrate to 1800-3600 mg/day in three divided doses. 1, 3
• No additional benefit demonstrated above 1800 mg/day, though doses up to 3600 mg/day are FDA-approved. 1, 3
• In elderly patients, start with 100-200 mg/day and titrate more gradually to minimize somnolence, dizziness, and mental clouding. 2
• Reduction in pain scores typically seen by Week 1 and maintained throughout treatment. 3, 4

Tricyclic Antidepressants (Alternative First-Line)

• Nortriptyline is preferred over amitriptyline, offering excellent efficacy (NNT = 2.64) with superior tolerability and equivalent analgesic benefit. 1, 5
• Start 10-25 mg at bedtime, increase every 3-7 days to target dose of 25-100 mg at bedtime. 5
• In elderly patients (≥65 years), start with 10 mg and titrate more slowly due to anticholinergic side effects. 1, 5
• Continue indefinitely until pain relief achieved, as PHN may persist for months to years. 5

Second-Line Treatment Options

Pregabalin

• Consider if inadequate response to gabapentin, with NNT of 4.93 and FDA approval for postherpetic neuralgia. 1, 6
• Effective dose: 150-600 mg/day in two divided doses, starting at 25-50 mg/day with gradual titration. 1, 6
• Pain reduction may occur as early as Week 1 and persist throughout treatment. 6
• Monitor for somnolence, dizziness, and mental clouding, especially in older patients. 1
• Adjust dose based on renal function (creatinine clearance 30-60 mL/min requires lower dosing). 6

SNRIs (Duloxetine, Venlafaxine)

• Duloxetine supported by two high-quality studies and five medium-quality studies for neuropathic pain. 1
• Start with lower doses and titrate slowly to minimize adverse effects in older adults. 1

Tramadol

• Shows efficacy with NNT of 4.76 as second-line option. 1

Third-Line Treatment Options

Opioids (Use with Caution)

• Oxycodone, extended-release morphine, and methadone show efficacy (NNT = 2.67) but should NOT be first-line agents. 1, 2
• Reserve for severe pain unresponsive to other treatments due to risks of pronociception, cognitive impairment, respiratory depression, endocrine/immunological changes, and potential for misuse and addiction. 1
• Combination therapy (morphine with gabapentin) may be more effective than single agents, allowing lower doses of each medication with additive effects. 1

Non-Pharmacological Approaches

• Cognitive behavioral therapy (CBT), hypnosis, and physical/occupational therapy may provide benefit. 1, 2
• Transcutaneous electrical nerve stimulation (TENS) has Level 2 evidence with grade B recommendation. 7
• Peripheral nerve stimulation shows promise for refractory cases, with one case report demonstrating 80% pain improvement. 7, 8

Interventional Therapies (Refractory Cases)

• Recommended sequence for interventional treatments: subcutaneous botulinum toxin A or triamcinolone injection, TENS, peripheral nerve stimulation, and stellate ganglion block first, followed by paravertebral block and pulsed radiofrequency if needed. 7
• Spinal cord stimulation may be considered for severe persistent pain. 7
• Dorsal root ganglion destruction and intrathecal methylprednisolone should be used with extreme caution due to destructiveness and adverse events. 7

Critical Pitfalls to Avoid

Medications NOT Recommended

• Lamotrigine is NOT recommended for PHN due to lack of efficacy evidence and risk of serious rash. 1, 2
• Corticosteroids provide NO benefit for established PHN and expose patients to unnecessary adverse effects including hyperglycemia, osteoporosis, hypertension, and immunosuppression. 1

Dosing Considerations

• Always adjust doses based on renal function in elderly patients to prevent toxicity. 2
• Monitor closely for neurological side effects (somnolence, dizziness, confusion) particularly problematic in older adults. 2
• Dizziness and somnolence with gabapentin are transient, occurring more frequently at doses <1800 mg/day than at higher doses. 9
• Peripheral edema with gabapentin increases at doses ≥1800 mg/day (7.5% vs 1.4% at lower doses). 9

Treatment Duration

• PHN may persist for months to years, requiring long-term treatment with no specified maximum duration for gabapentin or pregabalin therapy. 1, 5
• Periodic reassessment recommended as PHN may improve over time. 1