What Are Sulfonamides? Uses, Types, Side Effects, Precaution & Warning

Antibiotics of the sulfonamide class are often utilized in clinical practice to manage and cure bacterial diseases. In common parlance, these pharmaceuticals are called "sulfa medications." According to the Merck Manual, they are available in various dosage forms. 

Some of these dosage forms are designed for oral administration, while others are designed for topical application, vaginal usage, or ophthalmic (eye) application. Some of these dosage forms are also available in combination with one another.


According to the Science History Institute, the first antibacterial medications were commonly referred to as "sulfa pharmaceuticals." These treatments are credited with laying the groundwork for the widespread use of antibiotics later. In the 1930s, scientists set out to evaluate the efficacy of the first sulfonamide, Prontosil, in treating various illnesses.

According to the NIH or National Institutes of Health, as bacteria developed resistance to sulfonamides, penicillin eventually replaced sulfa medications as the major therapeutic option. It occurs because penicillin is more effective against multidrug-resistant bacteria. 

Even though there is still a problem with antibiotic resistance, sulfa medicines are regularly used to treat various bacterial infections. 

What Are Sulfonamides? 

The term "sulfonamides" refers to any medications that are part of the sulfonamide chemical group (sulphonamides). The name "sulfa medicines" is commonly used to refer to these types of pharmaceuticals.

Antibiotics, such as sulfonamides, are prescribed to patients to treat bacterial infections. Experts call it a synthetic medicine because it is not obtained from natural sources but created in a laboratory rather than taken from natural sources.

Antibiotics of the sulfonamide class are known for their broad spectrum of activity against various pathogens. This suggests that they are effective against a diverse range of pathogens, which are the responsible agents for the disease.

Uses of Sulfonamides

Sulfa medicines are successful because they prevent dihydropteroate synthase synthesis (DHPS). Folic acid, produced in part by DHPS, is an essential component for the proliferation of bacteria and is required for this process. The suppression of the enzyme will hamper the bacteria's growth and reproduction ability.

According to the Merck Manual, sulfa medicines can treat various illnesses, such as urinary tract infections (UTIs), inflammatory bowel disease (IBD), malaria, skin infections, vaginal infections, eye infections, and burns. According to research conducted, the medications do not work against viral diseases like the common cold or the flu.

Types of Sulfonamides

According to the experts, the following are examples of common sulfonamides −

  • Sulfasalazine (Azulfidine, Azulfidine EN-tabs) (Azulfidine, Azulfidine EN-tabs)

  • Diamox sequels (acetazolamide xr)

  • For children, a suspension of acetic acid and sulfisoxazole (Gantrisin)

  • Sulfisoxazole (Trixazole)

  • Zonisamide (Zonegran)

Precautions and Warnings

Experts warn that using sulfonamides over an extended period can cause damage to blood cells. A blood problem can increase the risk of infection, hinder the body's recovery capacity, and cause bleeding in the gums. You should use dental implements such as toothbrushes, floss, and toothpicks with extreme caution and postpone any dental operations until your blood counts have returned to normal.

You should inform your doctor if your symptoms do not improve while taking sulfonamides or if they worsen while you are on them.

Increased photosensitivity is one of the potential adverse effects caused by sulfonamides. Even a brief exposure to the sun can cause unpleasant side effects such as severe sunburn, a rash, itching, redness, or other skin discoloration. When taking these medications, always protect yourself from the sun by applying sunscreen, wearing protective clothing, and staying inside as much as possible.

When taking sulfonamides, it is preferable not to engage in activities that require one's whole mental focus, such as driving a vehicle or operating heavy machinery. These kinds of tasks require one's undivided attention. While on this medicine, your primary care physician will want to watch carefully how you are doing. Maintain all of your scheduled appointments at the clinic and the laboratory.

You are strongly encouraged to inform your physician that you are taking a sulfonamide before undergoing any medical or dental procedure. Sulfonamides should not be given to infants younger than two months of age unless specifically instructed to do so by a pediatrician. Because of their heightened sensitivity, sulfonamides should be administered to older patients with extreme caution, particularly if they are also taking diuretics (water pills).

Common Side Effects of Sulfonamides

Experts list the following as potential negative effects of sulfonamides

  • Itching

  • Red, itchy, and scaly skin

  • Sensitization of the skin to sunlight has increased

  • Diarrhea

  • Dizziness

  • Headache

  • lack of hunger

  • Irresistible need to throw up or experience nausea

  • Fatigue

Some other possible adverse effects are

  • Soreness in muscles and joints

  • Challenges with swallowing

  • white or very pale

  • Discoloration, soreness, blistering, peeling, or slackening of skin

  • Fever and sore throat

  • signs of abnormal bleeding or bruising

  • fatigue or a lack of strength that doesn't make sense

  • Discolored eyes or skin

Rare adverse effects may include

  • Sharp, stabbing pain in the abdomen, sometimes followed by vomiting

  • Pain in the belly

  • Discolored pee

  • severe and maybe bloody diarrhea

  • Urinary frequency or output that is extremely high or low

  • Dryness of the mouth

  • Lumbar pain

  • Alterations n one's mental or emotional state

  • Discomfort or burning when urinating

  • Head and neck swelling


Infectious bacteria are eliminated by the antibiotic class known as sulfonamides or sulfa medicines. These medication groups are typically broad-spectrum antibiotics, which kill numerous different bacteria and are used to treat various bacterial infections. Although sulphonamides do not directly kill germs, they inhibit the growth and multiplication of bacteria (bacteriostatic).

Bacteria require folic acid for optimal development and proliferation. Sulfa medicines prevent the bacteria from using folic acid, which helps their development. Thus, the germs are unable to multiply and spread. A human being is protected from the harmful effects of inhibiting folate production since the body does not produce folic acid and must obtain it only from its food.

It is common practice to combine trimethoprim with sulfa medications due to its bactericidal effects (bactericidal). Because of this, sulfonamides and trimethoprim inhibit bacterial growth and ultimately kill the germs. 

It is common practice to combine trimethoprim with sulfa medications due to its bactericidal effects (bactericidal). Because of this, sulfonamides and trimethoprim inhibit bacterial growth and ultimately kill the germs.