Can you apply more than one lidocaine (local anesthetic) patch at a time?

Lidocaine Patch Application Guidelines

Multiple lidocaine patches should not be applied simultaneously as this increases the risk of local anesthetic systemic toxicity (LAST). 1 The American Society of Anesthesiologists and other guidelines specifically caution against concurrent use of multiple local anesthetic interventions.

Maximum Safe Dosing

The primary concern with using multiple lidocaine patches is exceeding the maximum safe dose:

• The maximum safe dose of lidocaine should not exceed 9 mg/kg lean body weight for topical applications 2
• Lidocaine patches contain significant amounts of medication:
  • Standard 5% lidocaine patches contain 700 mg of lidocaine per patch 3
  • Newer 1.8% lidocaine systems contain 36 mg per patch but are bioequivalent to 5% patches 3

Risk Factors for Toxicity

Several factors increase the risk of lidocaine toxicity when using multiple patches:

• Applying patches to highly vascular areas increases absorption 1
• Patients with cardiac disease, electrolyte disorders, seizure disorders, renal/hepatic impairment, and neurological disorders are at higher risk 2, 1
• Concurrent use with other local anesthetic interventions significantly increases toxicity risk 2

Guidelines for Safe Use

The American Society of Anesthesiologists and other medical authorities recommend:

• Topical 5% lidocaine patches should be removed before starting any intravenous lidocaine infusion 2
• Lidocaine patches should not be used concurrently with other local anesthetic interventions 2, 1
• Continuous ECG, pulse oximetry, and regular blood pressure monitoring are required when using high doses of lidocaine 1

Signs of Lidocaine Toxicity

Be vigilant for early signs of toxicity, which occur in a dose-dependent manner:

• Early: Circumoral numbness, facial tingling, light-headedness, tinnitus 2, 1
• Moderate: Slurred speech, muscle twitching 2
• Severe: Seizures, cardiac arrhythmias, myocardial depression, respiratory arrest 2, 1

Proper Application Technique

For patients requiring coverage of larger painful areas:

• Use a single patch over the most painful area
• Consider alternative or adjunctive pain management strategies
• If multiple patches are absolutely necessary (rare cases), ensure:
  1. Total lidocaine dose remains below maximum safe dose
  2. Patient is closely monitored for signs of toxicity
  3. No other local anesthetics are used concurrently

Alternative Approaches

For patients with widespread pain requiring more coverage:

• Consider systemic medications appropriate for neuropathic pain
• Use multimodal pain management approaches with non-local anesthetic agents
• Consider referral to a comprehensive pain rehabilitation center for refractory cases 1

Remember that the risk of toxicity outweighs potential benefits of using multiple patches simultaneously in most clinical scenarios.