What is the best treatment approach for an elderly adult patient with a history of herpes zoster infection and experiencing zoster-related pain, considering the use of Lido (lidocaine) derm gel?

Lidocaine Topical Therapy for Zoster-Related Pain

For elderly adults with herpes zoster pain, the 5% lidocaine patch is a recommended first-line topical therapy that should be applied over the affected area for up to 12 hours daily (up to 3 patches), particularly valuable given its high safety profile and minimal systemic absorption in this vulnerable population. 1

Why Lidocaine Patch Over Gel

The lidocaine 5% patch is significantly more effective than lidocaine gel or cream for zoster-related pain. 2 In a case series of 34 patients with erythromelalgia (a condition with similar neuropathic pain mechanisms), most patients who used the 5% lidocaine patch noted improvement, in contrast to 10 previous patients who failed to respond to lidocaine gel. 2 The patches deliver lidocaine gradually over hours, providing sustained analgesia that topical gels cannot match. 2

Evidence-Based Application Guidelines

• Apply up to 3 patches for 12 hours per day over the affected dermatomal area, though some guidelines support up to 24-hour application. 1, 2
• The patch works by blocking sodium ion channels required for neuronal impulse conduction, resulting in local anesthesia. 2
• No systemic absorption or lidocaine toxicity has been documented with proper patch use, making it exceptionally safe for elderly patients. 2
• The 5% prescription strength is preferred over the 4% over-the-counter formulation for optimal efficacy. 2

Position in Treatment Algorithm

Acute Zoster Pain (First 72 Hours)

• Initiate antiviral therapy immediately (valacyclovir 1000 mg three times daily or famciclovir 500 mg every 8 hours for 7 days) within 72 hours of rash onset. 1, 3, 4
• Combine with stepped analgesia: Start acetaminophen (up to 3000-4000 mg/day divided) for mild pain, progress to opioids for moderate-severe pain. 1
• Add lidocaine 5% patch as adjunctive topical therapy for localized pain relief. 1

Preventing Postherpetic Neuralgia (PHN)

• Consider gabapentin early (starting 100-300 mg at bedtime, titrating to 300-600 mg three times daily) alongside conventional analgesics and topical lidocaine. 1
• Alternatively, use nortriptyline (10-25 mg at bedtime, slowly titrated) due to lower anticholinergic effects than amitriptyline in elderly patients. 1

Established PHN (Pain >90 Days)

• Lidocaine 5% patch remains a first-line option for localized neuropathic pain. 1, 5
• The patch demonstrated numerically higher pain response rates than pregabalin in PHN patients in limited comparative data. 5
• Efficacy is maintained long-term with excellent tolerability. 5

Critical Advantages in Elderly Patients

• Minimal drug interactions due to negligible systemic absorption, crucial for elderly patients on multiple medications. 5, 2
• Low adverse effect burden: Application site reactions are the most common events, typically mild to moderate. 5
• Avoids systemic side effects that plague oral medications in elderly patients (sedation, cognitive impairment, falls, anticholinergic effects). 1, 2
• Particularly valuable for patients with renal impairment who require dose adjustments of systemic medications. 2

Common Pitfalls to Avoid

• Do not use lidocaine gel as a substitute for the patch formulation—the patch's sustained delivery mechanism is essential for efficacy. 2
• Patients with severe, long-duration disease may respond less well to lidocaine patches; consider combination therapy earlier in these cases. 2
• Trial for at least 4 weeks before declaring treatment failure and switching to alternative topical agents. 2
• Avoid muscle relaxants (cyclobenzaprine, carisoprodol) and benzodiazepines in elderly zoster patients due to anticholinergic effects, sedation, and fall risk. 1

Alternative Topical Options if Lidocaine Fails

• Compounded amitriptyline 1-2% with ketamine 0.5% applied up to 3 times daily (can increase ketamine to 5% if needed). 2
• High-concentration capsaicin has moderate-quality evidence for PHN but is often poorly tolerated. 2, 1

Prevention Remains Paramount

The most effective strategy is preventing zoster through vaccination with Shingrix (recombinant zoster vaccine), which demonstrates 97.2% efficacy in adults ≥50 years. 1, 6 This should be recommended even for patients with previous zoster history. 1