A patient is allergic to both ester AND amide local anesthetics. What should you use?

If a patient is allergic to BOTH ester AND amide local anesthetics (true allergy to both classes), the alternative is DIPHENHYDRAMINE (Benadryl) 1% solution, which can be used as a local anesthetic by injection. It has intrinsic local anesthetic properties via sodium channel blockade. It's not ideal (shorter duration, more tissue irritation) but is the only safe option when both major LA classes are contraindicated. Mepivacaine and Prilocaine are amides. Benzocaine is an ester. A is correct.