Topical Anesthetics (Lidocaine, Prilocaine, Tetracaine, Benzocaine)

Also known as: numbing cream, EMLA (lidocaine/prilocaine), compounded BLT-type creams

DermatologyOther

In plain English

These are numbing medicines applied to the skin or mucous membranes before procedures such as injections, laser, microneedling, or minor surgery. Compounded 'numbing creams' combine one or more of lidocaine, prilocaine, tetracaine, and benzocaine and are left on (often under a covering) for 20-60 minutes to take effect. Used correctly on limited areas they are safe; applying strong numbing cream over large areas or under wrap can lead to dangerous absorption.

The science

These agents are ester (tetracaine, benzocaine) or amide (lidocaine, prilocaine) local anesthetics that block voltage-gated sodium channels, preventing nerve depolarization and pain transmission. The eutectic lidocaine/prilocaine (EMLA) formulation is well studied for dermal analgesia before needle sticks and minor dermatologic surgery; combined higher-strength compounded creams increase potency but also absorption risk.

References

• Buckley MM & Benfield P, eutectic lidocaine/prilocaine cream (EMLA) review, Drugs 1993
• Tran AN & Koo JY, risk of systemic toxicity with topical lidocaine/prilocaine (review), J Drugs Dermatol 2014