What Are Sulfonamides?

‘Sulfa drugs’ were some of the original antibiotics, and are still in use today.

Sulfonamides, or "sulfa drugs," are a group of medicines used to treat bacterial infections.

They may be prescribed to treat urinary tract infections (UTIs), bronchitis, eye infections, bacterial meningitis, pneumonia, ear infections, severe burns, traveler's diarrhea, and other conditions.

Sometimes, the medicines are also used to help control seizures and treat other medical concerns.

The drugs won't work for viral infections, such as a cold or the flu.

Sulfonamides work by preventing the growth of bacteria in the body.

They come in different formulations and may be taken as an oral, topical, vaginal, or ophthalmic (eye) medicine.

The discovery of sulfonamides paved the way for the widespread use of antibiotics. The first sulfonamide, Prontosil, was tested in the 1930s.

Common Sulfonamides

Commonly prescribed sulfonamides include:

• Gantrisin (sulfisoxazole)
• Bactrim or Septra (trimethoprim and sulfamethoxazole)
• Sulfadiazine
• Azulfidine (sulfasalazine)
• Zonegran (zonisamide)

Side Effects of Sulfonamides

Side effects of sulfonamides may include:

• Skin rash
• Itching
• Headache
• Dizziness
• Diarrhea
• Tiredness
• Nausea or vomiting
• Pale skin
• Joint pain
• Sensitivity to light

Allergies to Sulfonamides

Allergies to sulfonamides are common.

Tell your doctor if you have allergies to food dyes, preservatives, or animals.

Let your doctor know right away if you experience signs of a severe allergic reaction (anaphylaxis), which may include rash, hives, difficulty breathing, chest tightness, or swelling of the face, lips, or tongue.

Sulfonamide Warnings

Tell your doctor about all medical conditions you have — especially kidney, liver, or blood disorders — before taking a sulfonamide.

Sulfonamides may cause blood problems, especially if they're taken for a long period of time.

These medicines can also cause a serious, even life-threatening, skin rash. Tell your doctor right away if you notice a rash or unusual skin changes.

Your doctor will want to carefully monitor your body's response to this medicine with frequent observation. Keep all appointments with your doctor's office and laboratory.

These medicines shouldn't be given to infants under 2 months old.

Elderly people may be more sensitive to the side effects of sulfonamides. Talk to your doctor if you're over 65.

Tell your doctor about all prescription, non-prescription, illegal, recreational, herbal, nutritional, or dietary drugs you're taking before using sulfonamides.

Let your healthcare provider know you're taking a sulfonamide before having any type of medical procedure, including a dental exam or procedure.

These drugs may make your skin more sensitive to the sun. Avoid unnecessary exposure to sunlight, and wear sunscreen and protective clothing while outdoors.

Sulfonamides may make you dizzy. Don't drive or perform activities that require alertness until you know how your medicine affects you.

Tell your doctor if your symptoms don't improve or worsen after starting on a sulfonamide.

Sulfonamides and Pregnancy

Animal studies have shown that sulfonamides may cause birth defects.

Tell your doctor if you're pregnant, or might become pregnant, before taking any of these drugs.

These medicines can also pass into breast milk. Don't breastfeed while taking a sulfonamide.