What are sulfonamides?

Sulfonamides (sulfa drugs) are drugs that are derived from sulfanilamide, a sulfur-containing chemical. Most sulfonamides are antibiotics, but some are prescribed for treating ulcerative colitis. Sulfonamide antibiotics work by disrupting the production of dihydrofolic acid, a form of folic acid that bacteria and human cells use for producing proteins.

What are the side effects of sulfonamides?

Sulfonamides may cause:

• dizziness,
• headache,
• lethargy,
• diarrhea,
• anorexia,
• nausea,
• vomiting, and
• serious skin rashes.

Sulfonamides should be stopped at the first appearance of a skin rash before the rash becomes severe.

Serious rashes include:

• Stevens-Johnson syndrome, which includes symptoms like:
• aching joints,
• aching muscles,
• redness,
• blistering, and
• peeling of the skin
• Toxic epidermal necrolysis, which includes symptoms like:
  • difficulty in swallowing,
  • peeling,
  • redness,
  • loosening, and
  • blistering of the skin.

Sulfonamides also may cause sensitivity to the sun that leads to extensive sunburn after exposure to sunlight (photosensitivity). Patients receiving sulfonamides should avoid excessive exposure to sunlight and should wear sunscreen.

Other rare side effects include liver damage, low white blood cell count (leucopenia), low platelet count (thrombocytopenia), and anemia. Formation of urinary crystals which may damage the kidney and may cause blood. Adequate hydration is needed to prevent the formation of urinary crystals.

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Report Problems to the Food and Drug Administration

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.