What drugs should be avoided with a sulfa allergy?

People with a sulfa allergy typically need to avoid sulfonamide antibiotics (antibiotics containing sulfa), including:

• Septra and Bactrim (sulfamethoxazole-trimethoprim)
• Pediazole (erythromycin-sulfisoxazole)

Whether other nonantibiotic sulfa-containing drugs need to be avoided with sulfa allergy is unclear and considered on a case-by-case basis.

Sulfa can be found in many different drugs, but sulfonamide antibiotics cause the majority of sulfa allergies. Research is mixed on whether there is an association between allergies to antibiotic sulfa drugs and nonantibiotic sulfa drugs. Experiencing an allergic reaction to a sulfonamide antibiotic does not mean that you will react poorly to sulfonamide nonantibiotic drugs.

While the risk is low, people with an allergy to sulfa antibiotics may have a higher risk of reacting poorly to nonantibiotic sulfa drugs. It may be that sulfa antibiotic allergies are associated with a greater risk of drug allergies overall. One study reported in a review in Canadian Family Physician found that penicillin, which is substantially different from sulfa antibiotics, was more likely to cause an allergic reaction than sulfa nonantibiotics among people allergic to sulfa antibiotics.

Besides antibiotics, some of the drugs that contain sulfa include:

• Antivirals, such as amprenavir and fosamprenavir
• Carbonic anhydrase inhibitors, such as acetazolamide and brinzolamide
• COX-2 inhibitors, such as celecoxib and rofecoxib
• Loop diuretics, such as bumetanide and furosemide
• Sulfonylureas, such as acetohexamide and chlorpropamide
• Thiazide diuretics, such as benzthiazide and chlorothiazide
• Triptans, such as almotriptan and eletriptan

It is important for your doctor to be aware of your history of drug allergies so that you and your doctor can make careful decisions and weigh the risks and benefits in each case.

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