What are the treatment options for postherpetic neuralgia (PHN)?

Management of Postherpetic Neuralgia

Start with gabapentin as first-line oral therapy, titrating from 300 mg on day 1 to 900 mg on day 3, then up to 1800-3600 mg/day in three divided doses, or use topical lidocaine 5% patches for localized pain, particularly in elderly patients. 1, 2, 3

First-Line Treatment Options

Oral Pharmacotherapy

• Gabapentin is the American College of Physicians' recommended first-line oral agent, starting at 300 mg on day 1,600 mg on day 2 (divided twice daily), and 900 mg on day 3 (divided three times daily), with subsequent titration to 1800-3600 mg/day in three divided doses as needed for pain relief. 1, 3
• The FDA label confirms efficacy across the 1800-3600 mg/day range, though no additional benefit is demonstrated above 1800 mg/day. 1, 3
• Gabapentin has an excellent number needed to treat (NNT) of 2.64 and was effective in reducing pain by Week 1 in clinical trials. 1, 3

Topical Therapy (Preferred for Elderly/Localized Pain)

• Topical lidocaine 5% patches are the ideal first-line choice for elderly patients, offering excellent efficacy (NNT = 2) with minimal systemic absorption, making them particularly suitable for those with comorbidities. 1, 2
• The patches can be worn 12-24 hours on affected areas, delivering medication gradually with minimal side effects. 1
• Capsaicin 8% patches provide an alternative topical option with pain relief lasting at least 12 weeks, though erythema and pain are common side effects that can be mitigated by applying 4% lidocaine for 60 minutes before capsaicin application. 1, 2

Tricyclic Antidepressants

• Nortriptyline is preferred over amitriptyline due to better tolerability with equivalent analgesic benefit (NNT = 2.64), started at 10-25 mg at bedtime and increased every 3-7 days to 25-100 mg at bedtime as tolerated. 1, 2
• TCAs have excellent efficacy but are frequently contraindicated or poorly tolerated in elderly patients with PHN. 4

Second-Line Treatment Options

When Gabapentin Fails or Is Insufficient

• Pregabalin should be considered if gabapentin provides inadequate response, with an NNT of 4.93 and effective doses typically ranging from 150-600 mg/day in two divided doses. 1, 5
• The FDA label confirms pregabalin's efficacy for PHN in patients with pain persisting at least 3 months after herpes zoster rash healing, with pain reduction observed as early as Week 1. 5
• Dose adjustments are required based on creatinine clearance: patients with CLcr 30-60 mL/min should receive lower doses (75-150 mg twice daily) compared to those with CLcr >60 mL/min (up to 300 mg twice daily). 5

Opioid Therapy (Use with Caution)

• Opioids (oxycodone, extended-release morphine, methadone) show excellent 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 and may be considered as a safer opioid alternative. 1

Combination Therapy

• When single agents provide inadequate relief, combination therapy such as morphine with gabapentin may be more effective, allowing for lower doses of each medication while providing additive effects. 1, 2
• Combining gabapentin with nortriptyline is another rational approach when monotherapy fails. 6
• Recent evidence suggests that local anesthesia combined with gabapentin shows outstanding compatibility. 7

Special Considerations for Elderly Patients

• Start with lower doses and titrate more slowly in elderly patients, with topical treatments being particularly valuable due to minimal systemic effects. 1, 2
• For gabapentin in elderly patients, begin with 100-200 mg/day rather than the standard 300 mg starting dose. 2
• Always adjust doses based on renal function to prevent toxicity, as elderly patients are more likely to have decreased renal function. 2, 3
• Monitor closely for neurological side effects (somnolence, dizziness, confusion, mental clouding) that are particularly problematic in older adults. 1, 2

Non-Pharmacological Approaches

• Cognitive behavioral therapy (CBT), hypnosis, and physical and occupational therapy may be beneficial as adjunctive treatments. 1, 2
• For refractory cases with persistent intractable pain, interventional techniques such as peripheral nerve stimulation can be considered when conservative management fails. 8
• Electroacupuncture and osteopathic manipulative treatment show efficacy and are potential options to alleviate pain, especially for intractable cases. 7

Common Pitfalls and Contraindications

• Lamotrigine is NOT recommended for PHN due to lack of convincing evidence of efficacy and risk of lamotrigine-associated rash. 1, 2
• Avoid underdosing gabapentin—doses of 400 mg/day are far below the effective range for neuropathic pain control. 6
• Do not exceed 12 hours between gabapentin doses when using three-times-daily dosing. 3
• In patients with creatinine clearance <15 mL/min, reduce daily gabapentin dose in proportion to creatinine clearance, and provide supplemental post-hemodialysis doses. 3

Treatment Duration and Monitoring

• PHN is a chronic condition that may persist for months to years, and some patients require long-term treatment with no maximum duration specified in guidelines. 1
• Periodic reassessment of continued therapy is recommended, as PHN may improve over time. 1
• Some patients experience pain reduction as early as Week 1, which typically persists throughout treatment. 5, 3