What is the treatment for neuropathic pain after a herpes zoster (shingles) outbreak?

Treatment of Neuropathic Pain After Shingles Outbreak

Gabapentin is the first-line oral pharmacological treatment for post-herpetic neuralgia (PHN) following a shingles outbreak, with a recommended starting dose of 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

Gabapentinoids

• Gabapentin has demonstrated efficacy in clinical trials for PHN, with FDA approval specifically for this indication 2
• Start with low doses in older adults (100-200 mg/day) and gradually titrate to minimize side effects such as somnolence, dizziness, and mental clouding 3
• Effective doses typically range from 900-3600 mg/day in divided doses, though older adults may respond to lower doses 3, 2
• Pregabalin may be preferred for initial trials in some patients due to pharmacokinetics that support easier and more rapid titration, with effective doses ranging from 150-600 mg/day in two divided doses 3, 4

Topical Treatments

• Topical lidocaine patches (5%) provide excellent efficacy with minimal systemic absorption, making them particularly suitable for elderly patients or those with localized pain 1
• High-concentration capsaicin (8%) patches or cream can provide pain relief for up to 12 weeks, though application may cause temporary erythema and pain 1
• Consider applying 4% lidocaine for 60 minutes before capsaicin application to mitigate application-related discomfort 1

Tricyclic Antidepressants

• Tricyclic antidepressants (TCAs) have excellent efficacy with a number needed to treat (NNT) of 2.64 1
• Nortriptyline is preferred over amitriptyline due to better tolerability with equivalent analgesic benefit 1
• 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

Second-Line Treatment Options

Alternative Medications

• If gabapentin provides inadequate response, consider serotonin-norepinephrine reuptake inhibitors (SNRIs) 3, 1
• Tramadol shows efficacy with an NNT of 4.76 and may be considered when first-line agents fail 1
• 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, and potential for misuse 1

Combination Therapy

• Combining medications with different mechanisms of action may provide better pain relief than monotherapy 1, 5
• For example, combining gabapentin with topical agents may allow for lower doses of each medication while providing additive effects 1

Special Considerations

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 1
• Monitor closely for side effects such as somnolence, dizziness, and mental clouding with gabapentinoids 3

Treatment Algorithm

1. Start with gabapentin (first-line) with gradual titration to effective dose 1, 2
2. Add topical lidocaine or capsaicin for localized pain 1
3. If inadequate response, consider adding a TCA (preferably nortriptyline) 1
4. For refractory cases, switch to pregabalin or add an SNRI 3, 1
5. Consider opioids only when other options have failed 1

Common Pitfalls and Caveats

• Lamotrigine is not recommended for PHN due to lack of convincing evidence of efficacy and risk of lamotrigine-associated rash 3
• Do not stop gabapentin suddenly as this can cause serious problems; taper gradually when discontinuing 2
• Monitor for suicidal thoughts or actions, which can occur in approximately 1 in 500 patients taking gabapentin 2
• Medication side effects, especially sedation, may limit adherence and effectiveness, particularly in elderly patients 3
• Periodic reassessment of continued therapy is recommended, as post-herpetic neuralgia may improve over time 1