Allergy to which medication contraindicates the use of Bactrim?

The correct choice indicates that an allergy to hydrochlorothiazide contraindicates the use of Bactrim. Bactrim is a combination antibiotic that contains sulfamethoxazole and trimethoprim. Hydrochlorothiazide is a thiazide diuretic, and although not directly related to antibiotics, cross-reactivity can occur due to the sulfonamide component in Bactrim.

Patients who have a known allergy to hydrochlorothiazide may also have an increased risk of having an allergic reaction to sulfonamide drugs because both medications share a similar chemical structure. Therefore, it's essential to avoid Bactrim in these patients to prevent potential adverse reactions.

On the other hand, allergies to penicillin, aspirin, or cephalosporins do not typically contraindicate the use of Bactrim. While cross-reactivity between penicillin and cephalosporins is a well-known concern, it does not extend to sulfonamides like those in Bactrim. Similarly, aspirin allergies primarily relate to sensitivities involving NSAIDs and do not directly impact the use of Bactrim. Thus, understanding the specific risks associated with sulfa drugs is crucial for patient safety.