What are the treatment options for post herpetic neuralgia?

Treatment Options for Post-Herpetic Neuralgia

Start with gabapentin 300 mg on day 1,600 mg on day 2, and 900 mg on day 3, titrating to 1800-3600 mg/day in divided doses, or use topical lidocaine 5% patches for 12-24 hours daily if the patient is elderly or has significant comorbidities. 1

First-Line Treatment Algorithm

For Most Patients: Gabapentin

• Gabapentin is the recommended first-line oral treatment with dosing starting at 300 mg on day 1,600 mg on day 2, and 900 mg on day 3, then titrating up to 1800-3600 mg/day as needed for pain relief 1
• No additional benefit is shown above 1800 mg/day, so avoid escalating beyond this dose unless absolutely necessary 1
• For elderly patients specifically, start with 100-200 mg/day and titrate more gradually to prevent side effects 2
• Monitor for somnolence, dizziness, and mental clouding, particularly in older adults 1

For Elderly or Patients with Multiple Comorbidities: Topical Lidocaine

• Topical lidocaine 5% patches provide excellent efficacy (NNT = 2) with minimal systemic absorption, making them ideal for elderly patients 1, 2
• Apply patches for 12-24 hours on affected areas, delivering medication gradually over hours 1
• This option avoids systemic side effects that are problematic in older adults 2

Alternative First-Line: Tricyclic Antidepressants

• Nortriptyline has excellent efficacy (NNT = 2.64) and is preferred over amitriptyline due to better tolerability with equivalent analgesic benefit 1, 2
• Start at 10-25 mg at bedtime and increase every 3-7 days to a final dose of 25-100 mg at bedtime as tolerated 1
• This minimizes daytime sedation effects while providing strong pain relief 1

Second-Line Treatments (When First-Line Inadequate)

Pregabalin

• Consider pregabalin if gabapentin provides inadequate response, with an NNT of 4.93 1
• Effective dose typically ranges from 150-600 mg/day in two divided doses 1
• No maximum duration is specified in guidelines, as some patients require long-term treatment 1

High-Concentration Capsaicin

• The 8% capsaicin patch can provide pain relief for at least 12 weeks 1, 2
• Apply 4% lidocaine for 60 minutes before capsaicin application to mitigate erythema and pain side effects 1, 2

Tramadol

• Tramadol shows efficacy with an NNT of 4.76 1
• Consider this before moving to stronger opioids 2

Third-Line Treatments (Refractory Cases Only)

Opioids

• Oxycodone, extended-release morphine, and methadone show strong efficacy (NNT = 2.67) 1, 2
• However, these 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 for severe, refractory pain only 2

Combination Therapy

• Combining morphine with gabapentin may be more effective when single agents fail, allowing for lower doses of each medication while providing additive effects 1, 2
• This approach reduces individual medication side effects while improving pain control 1

Interventional Treatments (For Refractory Cases)

When conservative pharmacological options fail:

• Start with less invasive options: subcutaneous botulinum toxin A injection, transcutaneous electrical nerve stimulation (TENS), or stellate ganglion block 3
• Second tier: paravertebral block and pulsed radiofrequency 3
• Consider spinal cord stimulation or peripheral nerve stimulation if severe pain persists despite above measures 3
• Avoid dorsal root ganglion destruction and intrathecal methylprednisolone except as last resort due to destructiveness and adverse events 3

Non-Pharmacological Approaches

• Cognitive behavioral therapy (CBT), hypnosis, and physical/occupational therapy may provide additional benefit 1, 2
• These can be used adjunctively with pharmacological treatments 1

Critical Pitfalls to Avoid

• Never use lamotrigine for PHN - it lacks convincing evidence of efficacy and carries risk of serious skin rash 1, 2
• Always adjust doses based on renal function in elderly patients to prevent toxicity 2
• Avoid starting gabapentin at full doses in elderly patients - use 100-200 mg/day initially 2
• Do not exceed gabapentin 1800 mg/day expecting additional benefit 1
• Reassess therapy periodically, as PHN may improve over time and medication reduction may be possible 1