Alternative Local Anesthetics for Rapid Lidocaine Metabolizers

Patient Identification and Management

Patients with enhanced hepatic metabolism may experience shorter duration of anesthesia due to faster clearance, and factors affecting lidocaine metabolism include individual genetic variations in cytochrome P450 enzymes, drug interactions with medications that induce hepatic enzymes, and acid-base status 1
History of inadequate anesthesia with standard lidocaine doses and patients taking medications that induce cytochrome P450 enzymes can identify patients at risk for rapid lidocaine metabolism 1

Ester-type local anesthetics are useful for patients with true lidocaine allergy, with a different chemical structure and metabolic pathway than amides 2
Diphenhydramine (1%) can be used for small procedures, with a longer onset of action and limited efficacy compared to traditional local anesthetics 2, 3
Bacteriostatic saline (0.9% benzyl alcohol in normal saline) is an alternative for small excisions and biopsies, and may be less painful than diphenhydramine when combined with epinephrine 2, 3

Maximum safe dose of lidocaine is 7 mg/kg with epinephrine and 4.5 mg/kg without epinephrine, and should be calculated based on ideal body weight rather than actual body weight 2, 4, 5
Incremental dosing for longer procedures and monitoring for early signs of toxicity, such as circumoral numbness and facial tingling, are recommended 3
Avoid combining different local anesthetics without careful dose adjustment and wait at least 4 hours between different local anesthetic interventions 4, 5