What is the recommended treatment regimen for the Lidoderm (lidocaine) patch in postherpetic neuralgia?

Lidocaine Patch Treatment Regimen for Postherpetic Neuralgia

The lidocaine 5% patch (Lidoderm) should be applied to the area of greatest pain for 12 hours per day, with up to 3 patches worn simultaneously depending on the size of the painful area. 1, 2

Application Guidelines

• Apply lidocaine 5% patch to intact skin only, covering the most painful area for 12 hours daily, followed by 12 hours off to minimize skin irritation 1, 2
• Up to 3 patches may be used simultaneously, depending on the size of the painful area 3, 2
• Patches should be removed before applying heat or during activities that may cause excessive sweating to avoid increased systemic absorption 3
• The patch can be cut to fit the affected area if needed, but ensure complete skin contact for optimal effectiveness 3

Efficacy and Expected Outcomes

• Clinical studies show the lidocaine 5% patch provides significant pain reduction with approximately 60% of patients reporting moderate to complete pain relief 1
• Pain relief typically begins within the first week of treatment, with 66% of patients reporting improvement in pain intensity by day 7 1
• For patients who don't respond by day 7, approximately 43% may experience improvement by day 14, suggesting a trial of at least 2 weeks is appropriate 1
• The patch reduces both pain intensity and pain interference with quality of life, with 74% of patients reporting improved quality of life by day 7 1

Safety Profile and Monitoring

• Systemic absorption is minimal, making it particularly suitable for elderly patients or those with comorbidities 4, 2
• Most adverse events are limited to application site reactions (mild skin redness or irritation) 2, 5
• Monitor for signs of skin irritation or sensitization with periodic skin checks 3
• No clinically significant systemic adverse effects have been noted, even with long-term use 2

Anatomical Considerations

• Effectiveness is similar regardless of anatomic location (head/neck, trunk, or extremities) 5
• Application to the head/neck area may be associated with more adverse events compared to trunk or extremities 5
• For areas where patches may not adhere well, consider complementary use of lidocaine cream 3

Treatment Duration

• The lidocaine patch 5% is effective regardless of time since shingles onset, showing significant improvement even in longstanding PHN 1
• Treatment should be initiated as early as possible in the course of PHN for optimal results 1
• Long-term use is considered safe with minimal risk of systemic effects or drug-drug interactions 2

Combination Therapy

• The lidocaine patch 5% can be used alone or in combination with other agents for PHN 1
• Consider combining with other first-line agents such as gabapentin, pregabalin, or tricyclic antidepressants if monotherapy provides inadequate relief 4

Common Pitfalls and Caveats

• Avoid applying patches to broken or inflamed skin 3
• Do not use lidocaine patches within 4 hours of other local anesthetic interventions 3
• Remove patches before starting intravenous lidocaine therapy if indicated 3
• Brain imaging studies show that while short-term treatment (6 hours) affects sensory and affective pain pathways, longer-term treatment (2 weeks) is needed to modulate reward-related regions involved in chronic pain 6