Which drug is least likely to cause a sulfa allergy?

Aspirin is least likely to cause a sulfa allergy because it does not contain a sulfonamide group, which is the specific chemical structure that can trigger allergic reactions in individuals sensitive to sulfa drugs. Sulfa allergies are primarily associated with medications that include sulfonamide in their chemical composition, such as certain diuretics, antibiotics like Bactrim, and some non-steroidal anti-inflammatory drugs (NSAIDs) like Celebrex.

Since aspirin is a salicylate and does not belong to the sulfonamide class of drugs, it is not associated with the same risk for sulfa allergy reactions. This makes it a safer option for patients with known sulfa allergies compared to the other drugs listed.