Treatment of Postherpetic Neuralgia
For postherpetic neuralgia (PHN), start with topical lidocaine 5% patches (12-24 hours daily) or gabapentin (300 mg day 1,600 mg day 2,900 mg day 3, then titrate to 1800-3600 mg/day in three divided doses), as both are first-line treatments with excellent efficacy. 1
First-Line Treatment Options
Topical Therapies (Preferred for Elderly or Those with Comorbidities)
- Lidocaine 5% patches provide excellent pain relief (NNT = 2) with minimal systemic absorption, making them ideal for elderly patients or those with multiple comorbidities. 1, 2
- Apply patches for 12-24 hours on affected areas, delivering medication gradually over hours. 1
- Capsaicin 8% dermal patch can provide pain relief for at least 12 weeks, though erythema and pain are common side effects. 1
- To minimize capsaicin side effects, apply 4% lidocaine for 60 minutes before capsaicin application. 1, 2
Oral Pharmacological Therapies
Gabapentin is recommended as 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 in three divided doses. 1, 3
No additional benefit is shown above 1800 mg/day, though the FDA label supports dosing up to 3600 mg/day. 1, 3
In elderly patients, start with 100-200 mg/day and titrate more gradually to minimize somnolence, dizziness, and mental clouding. 2
Pain reduction can be seen as early as Week 1 and is maintained throughout treatment. 3, 4
Tricyclic antidepressants (TCAs) have excellent efficacy (NNT = 2.64), with nortriptyline strongly preferred over amitriptyline due to better tolerability with equivalent analgesic benefit. 1, 5
Start nortriptyline at 10-25 mg at bedtime, increase every 3-7 days as tolerated, targeting 25-100 mg at bedtime. 1, 5
In elderly patients, start with 10 mg and titrate more slowly. 5
Continue indefinitely until pain relief is achieved, as PHN may persist for months to years. 5
Second-Line Treatment Options
Pregabalin should be considered if gabapentin provides inadequate response, with an NNT of 4.93 and effective dosing of 150-600 mg/day in two divided doses. 1, 6
Start with 25-50 mg/day and titrate to the effective dose range. 1
Pain reduction can occur as early as Week 1 and persists throughout treatment. 6
Monitor for somnolence, dizziness, and mental clouding, especially in older patients. 1
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. 1, 2
Tramadol shows efficacy with an NNT of 4.76. 1
Combination therapy, such as morphine with gabapentin, may be more effective when single agents provide inadequate relief, allowing for lower doses of each medication while providing additive effects. 1, 2
Non-Pharmacological Approaches
- Cognitive behavioral therapy (CBT), hypnosis, and physical and occupational therapy may be beneficial for PHN management. 1
Treatment Duration
- PHN is a chronic condition that may persist for months to years, requiring long-term treatment with periodic reassessment. 1, 5
- No maximum duration is specified for pregabalin or gabapentin therapy when clinically indicated. 1
- The probability of pain relief correlates strongly with early treatment initiation after rash onset. 5
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, 2
- Always adjust doses based on renal function in elderly patients to prevent toxicity, particularly with gabapentin and pregabalin. 2
- Monitor closely for neurological side effects (somnolence, dizziness, confusion) that are particularly problematic in older adults. 1, 2
- Gabapentin for prevention of PHN during acute herpes zoster is not effective and should not be used for this indication. 7, 8