Which medication is listed as a pretreatment drug for known allergies prior to a procedure?

• A. Diphenhydramine (Benadryl)
• B. Lidocaine
• C. Epinephrine
• D. Atropine

Answer: (A)

Diphenhydramine works as a pretreatment to blunt allergic reactions by blocking histamine H1 receptors. Histamine release during allergic responses causes symptoms such as itching, hives, swelling, and bronchospasm. Giving an antihistamine before a procedure that carries a known allergy risk (like exposure to contrast dye or certain anesthetics) helps reduce the severity or likelihood of these symptoms.

Lidocaine is a local anesthetic and isn’t used to prevent allergic reactions systemically. Epinephrine treats anaphylaxis or acute severe reactions, not as a routine preventive measure. Atropine is an anticholinergic used to reduce secretions or manage bradycardia, not for allergy prophylaxis.