From the Guidelines
A crossover reaction between intramuscular (IM) lidocaine and topical lidocaine is rare, with a genuine immunologic reaction representing only 1% of all adverse reactions to these medications 1.
Key Points
- Patients who experience an allergic reaction to IM lidocaine may also react to topical lidocaine formulations, although the likelihood is low 1.
- The reaction may manifest as localized skin irritation or erythema, and caution is advised when administering topical lidocaine to patients with a known history of IM lidocaine allergy.
- For patients with a true allergy to lidocaine, switching to an ester type of local anesthetic is an option, as cross-reaction between amide and ester types is rare 1.
Considerations
- Paraben allergy in preservative-containing amide preparations or cosensitization may contribute to the rare cross-reactions between amide and ester local anesthetics 1.
- Alternative anesthetics, such as 1% diphenhydramine or bacteriostatic saline, may be useful for small excisions and biopsies in patients with sensitivity or allergy to lidocaine 1.
From the Research
Crossover Reaction between Intramuscular (IM) Lidocaine and Topical Lidocaine
- The crossover reaction between IM lidocaine and topical lidocaine is not directly addressed in the provided studies, as they focus on the pharmacokinetics, bioequivalence, and safety of topical lidocaine formulations 2, 3, 4, 5, 6.
- However, the studies suggest that topical lidocaine can cause allergic contact dermatitis and delayed hypersensitivity reactions, which may be relevant to the crossover reaction with IM lidocaine 2, 3.
- The bioequivalence of different topical lidocaine formulations, such as lidocaine topical system 1.8% and lidocaine patch 5%, has been demonstrated, indicating that the drug delivery and absorption profiles of these formulations are similar 4, 5.
- The safety and efficacy of topical lidocaine formulations, including a rapid-acting topical 4% lidocaine gel, have been evaluated, and the results suggest that these formulations can provide effective anesthesia without causing toxic blood levels of lidocaine 6.
- The studies do not provide direct evidence on the crossover reaction between IM lidocaine and topical lidocaine, but they suggest that the pharmacokinetics and safety profiles of topical lidocaine formulations are well-characterized, and that allergic reactions and delayed hypersensitivity may be a concern for some patients 2, 3.