Treatment of Herpetic Neuralgia
Acute Herpes Zoster (Within 72 Hours of Rash Onset)
Start antiviral therapy immediately—valacyclovir, famciclovir, or acyclovir—within 72 hours of rash onset to reduce acute pain severity, shorten rash duration, and lower the risk of post-herpetic neuralgia. 1
Begin gabapentin with aggressive early titration: 300 mg on day 1,600 mg on day 2,900 mg on day 3, then escalate to 1800–3600 mg/day in divided doses for optimal acute pain control and prevention of post-herpetic neuralgia. 1
Famciclovir 500 mg three times daily for 7 days shortens median time to full crusting from 7 days (placebo) to 5 days, with greater benefit when initiated within 48 hours and in patients ≥50 years old. 2
Apply topical lidocaine 5% patches for 12–24 hours daily to provide excellent localized relief (NNT ≈ 2) with minimal systemic absorption, particularly valuable in elderly patients. 1
Critical pitfall: Doses of gabapentin below 1800 mg/day are sub-therapeutic; the American College of Physicians emphasizes that 400 mg/day is far below the therapeutic range. 1
Established Post-Herpetic Neuralgia (Pain Persisting ≥3 Months)
Post-herpetic neuralgia is defined as pain persisting ≥3 months after rash resolution and may last months to years, requiring long-term treatment in many patients. 3
First-Line Pharmacologic Options
Gabapentin 1800–3600 mg/day (divided doses) is the first-line oral agent, with efficacy demonstrated across this range and no additional benefit above 1800 mg/day. 1, 4
Nortriptyline is preferred over amitriptyline due to better tolerability with equivalent analgesic benefit (NNT ≈ 2.6); start 10–25 mg at bedtime, titrate every 3–7 days to 25–100 mg at bedtime, and in older adults begin at 10 mg with slower titration. 1, 4
Topical lidocaine 5% patches provide excellent efficacy (NNT = 2) with minimal systemic absorption, making them especially suitable for elderly patients or those with comorbidities. 1, 4
Capsaicin 8% patch applied once provides pain relief for at least 12 weeks; pretreat the area with 4% lidocaine for ~60 minutes to reduce burning and erythema. 1, 4
Common adverse effects of gabapentin include somnolence, dizziness, and ataxia in approximately 80% of patients, though these are generally tolerable; gabapentin also improves sleep quality, which is beneficial since pain often disrupts sleep. 1
Second-Line Pharmacologic Options
Pregabalin 150–600 mg/day (divided doses) is an alternative when gabapentin is ineffective or not tolerated (NNT ≈ 4.9). 1, 4
Duloxetine or venlafaxine (SNRIs) may be considered based on their efficacy in other neuropathic pain conditions, particularly when depressive symptoms coexist. 1, 4
Tramadol offers moderate efficacy for post-herpetic neuralgia (NNT ≈ 4.8). 1, 4
Opioids such as oxycodone, extended-release morphine, or methadone have demonstrated efficacy (NNT ≈ 2.7) but should not be first-line because of risks of cognitive impairment, respiratory depression, endocrine changes, and addiction. 1, 4
Combination Therapy
- Combination therapy—e.g., gabapentin + nortriptyline or morphine + gabapentin—can achieve better pain control while allowing lower doses of each agent, providing additive effects when single agents fail. 1, 4
Special Population Considerations
Elderly Patients
In older adults, initiate all medications at lower doses and titrate more slowly to minimize adverse effects, particularly somnolence, dizziness, and mental clouding, which increase fall risk. 1, 4
Topical lidocaine patches are especially valuable for the elderly due to minimal systemic exposure. 1, 4
Duloxetine 30–60 mg daily, titrating to 60–120 mg daily, offers neuropathic pain relief with less fall risk than tricyclics. 4
Avoid benzodiazepines, including clonazepam, due to their dramatic increase in fall risk in the elderly. 4
Pregnant Patients
Topical lidocaine 5% patches are the safest and most appropriate first-line therapy for post-herpetic neuralgia in pregnancy, delivering excellent pain relief with minimal systemic absorption and no known fetal risks. 4
Benzodiazepines should be avoided entirely in pregnant patients because they provide no analgesic benefit and carry a high risk profile. 4
Intrathecal or epidural injections are contraindicated during pregnancy unless absolutely required for maternal survival. 4
Nortriptyline and amitriptyline demonstrate strong efficacy (NNT ≈ 2.64) but cross the placenta; consider only after topical therapies have failed and when pain severely compromises maternal health. 4
Critical Pitfalls to Avoid
Lamotrigine should not be used for herpes zoster pain because it lacks convincing efficacy and carries a risk of serious rash. 1, 4
Systemic corticosteroids provide no benefit for established post-herpetic neuralgia and expose patients to hyperglycemia, osteoporosis, hypertension, and immunosuppression. 1, 4
Do not underdose gabapentin; doses <1800 mg/day are typically sub-therapeutic. 1, 4
Duration of Therapy and Prognosis
Post-herpetic neuralgia may persist for months to years; approximately 50% of individuals aged ≥60 years with herpes zoster develop post-herpetic neuralgia, and the condition can require lifelong management. 3
No predefined maximum duration exists for pregabalin or nortriptyline when clinically indicated; nortriptyline can be continued indefinitely until satisfactory pain relief is achieved, with periodic reassessment. 1, 3
The overall prognosis for complete resolution is poor; only a small proportion of patients achieve full recovery, although the disease typically does not worsen over time. 3
Approximately 90% of post-herpetic neuralgia patients exhibit allodynia with sensory deficits to temperature or pinprick stimuli, reflecting significant nerve injury that contributes to chronicity. 3
Counsel patients that treatment goals focus on pain reduction rather than rapid or complete elimination; expectations for swift resolution should be avoided. 3
Interventional Options
If pain is not sufficiently reduced with pharmacologic therapy, interventional treatment such as epidural injection with local anesthetics and corticosteroids or pulsed radiofrequency of the dorsal root ganglion are options. 5
Thoracic transforaminal epidural steroid injections can be considered an early treatment for post-herpetic neuralgia, though several courses may be required to achieve adequate and prolonged symptom control. 6