Management of Postherpetic Neuralgia
Gabapentin is the recommended first-line oral pharmacological treatment for postherpetic neuralgia (PHN), starting at 300 mg on day 1,600 mg on day 2, and 900 mg on day 3, titrating up to 1800-3600 mg/day as needed for pain relief. 1, 2
First-Line Treatment Options
Gabapentin: Start with 300 mg on day 1,600 mg on day 2, and 900 mg on day 3, with subsequent titration to 1800 mg/day in three divided doses. Clinical studies demonstrated efficacy across doses from 1800-3600 mg/day, but additional benefit beyond 1800 mg/day was not demonstrated 2
Tricyclic antidepressants (TCAs): Excellent efficacy with a number needed to treat (NNT) of 2.64, with nortriptyline preferred over amitriptyline due to better tolerability with equivalent analgesic benefit 1
Topical lidocaine 5% patch: Effective for postherpetic neuralgia with minimal systemic absorption, making it particularly suitable for elderly patients or those with comorbidities 3, 1
Capsaicin patches/cream: Available as an 8% dermal patch or cream, providing pain relief for at least 12 weeks. Note that application may cause erythema and pain, which can be mitigated by applying 4% lidocaine for 60 minutes before capsaicin application 1
Second-Line Treatment Options
Pregabalin: Consider if patients have an inadequate response to gabapentin, with effective doses typically ranging from 150-600 mg/day in two divided doses 1, 4
SNRIs (Serotonin-norepinephrine reuptake inhibitors): May be considered if first-line agents provide inadequate response 1
Opioids: Certain opioids (oxycodone, extended-release morphine, methadone) show 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 3, 1
Special Considerations for Elderly Patients
Start with lower doses and titrate more slowly in elderly patients 1
Topical treatments are particularly valuable for elderly patients due to minimal systemic effects 3, 1
For patients with renal impairment, dosage adjustment is necessary for gabapentin:
- 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 2
Combination Therapy
When single agents provide inadequate relief, combination therapy may be more effective, allowing for lower doses of each medication while providing additive effects 1
For example, combining gabapentin with topical lidocaine patches may provide better pain control with fewer systemic side effects 1
Monitoring and Side Effects
Monitor for common side effects of gabapentin, including:
- Dizziness and somnolence (most common, particularly during titration)
- Peripheral edema (more common at doses ≥1800 mg/day) 5
Interestingly, dizziness and somnolence appear to be transient and do not necessarily worsen with titration to higher doses of gabapentin 5
For pregabalin, monitor for similar side effects as gabapentin, including dizziness, somnolence, and peripheral edema 4
Non-Pharmacological and Interventional Approaches
Consider cognitive behavioral therapy, hypnosis, and physical therapy as adjunctive non-pharmacological approaches 1
For refractory cases, interventional treatments may be considered, including:
- Transcutaneous electrical nerve stimulation
- Local botulinum toxin A injections
- Stellate ganglion block
- Peripheral nerve stimulation 6
Common Pitfalls and Caveats
Lamotrigine is not recommended for PHN due to lack of convincing evidence of efficacy and risk of lamotrigine-associated rash 1
Benzodiazepines have limited efficacy in persistent pain management and carry high risk profiles in older adults 3
Gabapentin has limited absorption due to a saturable L-amino acid transport system, which is why it's typically administered in three divided doses for optimal efficacy 7
Preventive use of gabapentin during acute herpes zoster has not been shown to prevent the development of PHN 8