Sulfonamides are medicines that prevent the growth of bacteria in the body, and sulfa drugs are used to treat bacterial infections of different kinds. Sulfonamide group of drugs may be with or without antibiotic characteristics. Common sulfonamide antibiotics are sulfamethoxazole, trimethoprim/sulfamethoxazole, and erythromycin-sulfisoxazole. Besides these, there are many other medications, like furosemide (Lasix), hydrochlorothiazide (Microzide), glyburide (Glynase, Diabeta, Micronase), glimepiride (Amaryl), celecoxib (Celebrex), and sumatriptan (Imitrex), which contain sulfonamide.
Approximately 3% of the general population shows the symptoms of sulfa drugs allergy when treated with sulfonamide and other similar antibiotics. People with immune system-related diseases like AIDS, are more prone to developing this allergy and show a much higher prevalence of about 60%. Patients showing hypersensitivity reaction to any one member of the sulfonamide class are likely to have a similar reaction with others. Sulfa allergy may also lead to Stevens-Johnson Syndrome (SJS) which is a highly acute, immune-complex-mediated hypersensitivity condition that affects the skin and mucous membranes.
Antibacterial sulfonamides are synthetic antimicrobial agents that contain the sulfonamide group. They are structurally different from non-antibiotic sulfonamides and are more likely known to result in allergic reactions. Sulfa drugs are generally known to cause allergies, therefore, the medications should be carefully prescribed. Sulfates and sulfites are chemically unrelated to the sulfonamide group, and do not cause the same hypersensitivity reactions which are seen in the case of sulfonamide medications.
The following symptoms are generally seen in people suffering from this allergy.
Skin and Lung Reactions
Skin reaction is one of the most common reactions associated with these drugs. The adverse effects related to skin may range from skin rashes, to life-threatening Stevens-Johnson Syndrome (SJS), and toxic epidermal necrolysis. In some cases, an increased sensitivity to sunlight (photosensitivity) may also be observed. Sulfa medication and allergy can also affect the lungs with pneumonia-like reactions and worsen asthma problems.
The blood cells can be affected resulting in a decrease in the number of white blood cells, red blood cells, and platelets.
Aching Joints and Muscles
It may also result in a sensation of severe pain in the joints and muscles. Both the symptoms occur within a week or two after the medication starts.
An allergy to sulfa drugs can also worsen asthma due to its effect on the lungs.
The diagnosis is usually made when a person on sulfa medication experiences the allergy symptoms. There are no specific skin or blood tests available to diagnose sulfa allergy. In most of the cases, if a person is diagnosed with allergy, the sulfa medication is immediately stopped. However, merely avoiding medicines with 'sul' or 'sulfa' prefix is not the rule of thumb in this type of allergy, as there are many generic or brand names of medications that contain sulfonamides and which may not necessarily start with these prefixes.
In some cases, a person requiring sulfa drugs can be desensitized to the medication by giving very small amounts of the medication initially and then gradually increasing the amount over a period of time. This process helps the body to tolerate the medication. Allergic reactions to drugs are usually self-limiting and last only for a few days after the drug is discontinued. If the allergy symptoms are very severe, the patient should be treated by an allergist, who is experienced in the management of drug allergies.
Disclaimer: This HealthHearty article is for informative purposes only and should not be used as a replacement for expert medical advice.