What are the treatment options for post herpetic neuralgia?

Treatment for Post Herpetic Neuralgia

Gabapentin is recommended as first-line therapy for post herpetic neuralgia (PHN), starting at 300 mg on day 1,600 mg on day 2,900 mg on day 3, and titrating to 1800-2400 mg/day in divided doses, with an adequate trial period of 4-6 weeks. 1

First-Line Pharmacological Options

Anticonvulsants

• Gabapentin:

  • Initiate at 300 mg on day 1,600 mg on day 2,900 mg on day 3 1, 2
  • Target dose: 1800-2400 mg/day in three divided doses 2
  • Clinical studies demonstrated efficacy across 1800-3600 mg/day, but additional benefit above 1800 mg/day was not demonstrated 2
  • Requires 4-6 week adequate trial period 1
  • Common side effects: dizziness, somnolence

• Pregabalin:

  • Alternative to gabapentin 1
  • Dosage: 150-600 mg/day 1
  • Similar side effect profile to gabapentin (dizziness, somnolence, peripheral edema) 1
  • May have better absorption profile than gabapentin

Topical Treatments

• 5% Lidocaine patch:

  • First-line topical treatment 1
  • Up to 3 patches used simultaneously 1
  • Requires at least 4-week trial period 1
  • Minimal systemic side effects, making it particularly suitable for elderly patients

• High-concentration capsaicin:

  • Provides pain relief for at least 12 weeks 1
  • Pre-treatment with 4% lidocaine for 60 minutes recommended to reduce application discomfort 1

Second-Line Pharmacological Options

Antidepressants

• Tricyclic antidepressants (e.g., amitriptyline, nortriptyline):

  • Use with caution in elderly patients (>65 years) due to anticholinergic effects 1
  • Start at lower doses and titrate slowly in elderly patients 1
  • Monitor for drug interactions, especially in patients with polypharmacy 1

• Duloxetine:

  • Associated with small improvements in neuropathic pain 1

Special Considerations for Dosing

Renal Impairment

• Gabapentin dosage adjustment based on creatinine clearance 2:

  • CrCl ≥60 mL/min: 300-1200 mg three times daily
  • CrCl 30-59 mL/min: 200-700 mg twice daily
  • CrCl 15-29 mL/min: 200-700 mg once daily
  • CrCl <15 mL/min: 100-300 mg once daily
  • Hemodialysis patients require supplemental post-hemodialysis doses 2

• Pregabalin dosage adjustment also required in renal impairment 3

Elderly Patients

• Start at lower doses and titrate more slowly 1
• Increased risk of adverse effects, particularly with tricyclic antidepressants 1
• Dose should be adjusted based on creatinine clearance values 2

Non-Pharmacological Interventions

• Cognitive Behavioral Therapy (CBT): Helps address maladaptive behaviors related to pain 1
• Physical Therapy: Recommended for chronic pain management 1
• Transcutaneous electrical nerve stimulation (TENS): Non-invasive option with no serious adverse effects 1
• Hypnosis: Recommended for neuropathic pain (strong recommendation, low evidence) 1

Interventional Procedures for Refractory Cases

• Pulsed radiofrequency (PRF) targeting the dorsal root ganglion: Effective with long-term efficacy 1
• Botulinum toxin A injections: 50-100 units divided across affected dermatomes, minimal side effects, 3-4 months duration 1
• Stellate ganglion block: Prioritized if PHN duration is less than 1 year (75% improvement if used within 1 year) 1
• Spinal cord stimulation and peripheral nerve stimulation: Third-tier options for refractory cases 1

Prevention of PHN

• Antiviral therapy started within 72 hours of rash onset reduces acute pain and risk of PHN 1
• Oral acyclovir, famciclovir, or valacyclovir recommended 1
• Immunocompromised patients may require intravenous antiviral therapy 1

Treatment Algorithm

1. First step: Start gabapentin or pregabalin, potentially with topical lidocaine patch
2. If inadequate response after 4-6 weeks: Consider adding or switching to tricyclic antidepressant
3. If still inadequate response: Consider high-concentration capsaicin
4. For refractory cases: Consider interventional procedures starting with botulinum toxin or stellate ganglion block if <1 year duration
5. Last resort: Consider spinal cord or peripheral nerve stimulation

Common Pitfalls and Caveats

• Inadequate trial duration: Ensure 4-6 weeks of treatment at therapeutic doses before declaring treatment failure
• Insufficient dosing: Many patients require gradual titration to effective doses
• Overlooking renal function: Always adjust dosing based on creatinine clearance
• Ignoring side effects in elderly: Start at lower doses and titrate more slowly
• Neglecting non-pharmacological approaches: Incorporate physical therapy and CBT for comprehensive management