Locations:
More than 90 years ago, sulfonamides changed modern medicine. These were some of the first widely used antibiotics. While penicillin soon overshadowed them as an antibiotic, sulfonamides are still very commonly used today to treat dozens of different conditions. In the U.S., there are over 40 sulfonamide drugs still approved for use.
Advertisement
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy
Sulfonamides, also known as sulfa drugs, are a class of synthetic (not naturally occurring) medications. They get their name from what they all have in common: a particular part of their chemical structure that contains sulfur.
Advertisement
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy
Sulfonamides’ mechanism of action — or how they work — is to block how bacteria make folate (vitamin B9). They don’t actually kill bacteria. Without folate, the bacteria essentially starve to death.
We mainly get folate from food. That means sulfonamides don’t usually affect us the same way (except with certain rare medical conditions).
Sulfonamides weren’t the first antibiotics. But they were some of the best antibiotic drugs available for about a decade after their discovery. Deaths from infectious diseases fell by 28% in the U.S. after sulfonamides became widely available in the mid-1930s. But today, treating bacterial infections isn’t their only use. They also treat a wide variety of other conditions.
When sulfonamides first became available, their uses included treating and preventing bacterial infections. This lasted until penicillin use expanded in the mid-1940s.
Today, sulfonamides treat a huge range of conditions, from Type 2 diabetes and high blood pressure to HIV and melanoma.
The following sulfonamide antibiotics are currently U.S. Food and Drug Administration (FDA)-approved:
Advertisement
These nonantibiotic sulfonamide drugs (including what they treat or are used for) also currently have FDA approval:
Yes, you can be allergic to sulfonamide drugs. About 3% to 8% of people worldwide have an allergy to one of the sulfa drugs. But penicillin has a similar allergy rate. And researchers now know that just because you’re allergic to one sulfonamide doesn’t necessarily mean you’re allergic to all of them.
If you have a history of allergy to a sulfonamide, talk to a healthcare provider or pharmacist. They may be able to find you an alternate sulfonamide medication or suggest an alternative from another drug class.
Sulfonamides have a few drawbacks. They include:
These drawbacks can vary widely depending on the medication. Because of that, your healthcare provider is the best source of information for medications in your specific case.
Partly, yes. Bactrim™ contains the sulfonamide drug sulfamethizole. It also contains trimethoprim, which works similarly to sulfonamides but isn’t one.
Yes, celecoxib (often known under the brand name Celebrex®) is a sulfonamide.
Sulfa drugs can sometimes cause crystals to form in your pee (urine). This isn’t a common side effect, and you may be able to avoid it. Your healthcare provider can tell you if a drug you take is likely to cause them and what you can do to avoid having them.
Advertisement
With more than 90 years of history to back them, sulfonamide drugs have a tried-and-true reputation. But they’ve come a long way from where they started. They still treat bacterial infections like they did when they were first discovered. But now, they also treat dozens of other conditions, from head to toe.
If you have questions or concerns, talk to your healthcare provider or pharmacist. They can give you detailed information specific to your case. That way, you can try to maximize the benefits of these medications and limit any unwanted effects.
Advertisement
Last reviewed on 02/26/2025.
Learn more about the Health Library and our editorial process.
