A 30-year-old woman reports that a dental procedure with a procaine-based injection years ago caused generalised urticaria and facial swelling requiring hospital admission. For a planned minor skin excision under infiltration anaesthesia, which agent should be selected?

• A Benzocaine
• B Procaine
• C Tetracaine
• D Lignocaine (lidocaine) ✓

Explanation

True IgE-mediated allergy to local anaesthetics is essentially confined to the ester group and is directed mainly against para-aminobenzoic acid, the common metabolite of all esters. Procaine, tetracaine and benzocaine all generate PABA, so an ester-allergic patient should receive an amide such as lidocaine, whose allergic reactions are vanishingly rare and unrelated to PABA. Cross-reactivity between esters is expected, so switching to another ester would repeat the event.

Reference: Katzung Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.