<prompt> If a patient is absolutely allergic to LA, the specific drug used in place of it is:Chlorpheniramine maleateBenzalkonium chlorideDiphenhydramine hydrochlorideKetamine hydrochloride  <response>: If the patient is allergic:To ester local anesthetics, try an amide local anesthetic.To amide local anesthetics, try an ester local anesthetic.To methylparaben or is allergic to both amide and ester local anesthetics, try a MPF product.To antioxidants or sulfite compounds, review the product ingredients.Some drugs like pheniramine, promethazine, diphenhydramine have strong while others have weak membrane stabilizing property.MPF Methyl paraben Free Reference : KDT pharmacology 8th ed page no 180 