Sulfonamides are a group of drugs with or without antimicrobial properties. Hypersensitivity is usually attributed to the antibiotic class commonly called Sulfa drugs.

Mechanism of the allergic reaction

There are a number of medications containing sulfonamides. Usually their generic names have a prefix “sulfa-“, or “sul” Examples include sulfamethoxazole, sulfadiazine, erythromycin-sulfisoxazole, trimethoprim sulfamethoxazole. It is also present in other drugs such as furosemide, hydrochlorthiazide, glimepiride, imitrex, probenecid, celecoxib, and acetazolamide. However, allergy to sulfa drugs does not necessarily mean that the person also has an allergy to compounds containing sulfur. People who have HIV or AIDS are more likely to experience hypersensitivity to this drug category with a prevalence of 65%.

The pathophysiology is almost the same with other drug allergies. In most cases the symptoms affects various organ systems of the body:

• Dermatologic

May range from rashes, edema, photosensitivity, and urticaria, to the fatal Stevens-Johnson syndrome to Lyell’s syndrome or toxic epidermal necrosis

• GI

Fulminant hepatic necrosis

• Respiratory

Difficulty of breathing, wheezing, asthma exacerbations

• Blood components

Bone marrow depression manifested by agranulocytosis, hemolytic and aplastic anemia, thrombocytopenia.

What your Doctor can do for you

The diagnosis of sulfa allergy is based on evident clinical manifestations following the ingestion of sulfa medication. And the only way to treat the condition is to withhold the administration of the drug and the avoidance of medications that contain sulfonamide. Stevens-Johnson Syndrome and the rest of the symptoms will be needing supportive therapy.  Desensitization may be necessary to reduce the hypersensitivity to the drug.

What you can do

If you suspect any allergic reaction after taking sulfa drugs, discontinue the intake of any sulfa medication and report this immediately with your allergist.