Sulfonamides: Definition, Classification & Examples

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Kirstyn Wade

Kirstyn is a registered nurse and has a master's degree in Nursing Education. She has taught college Nursing courses.

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Christianlly Cena

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Sulfonamides are medications used to treat many different disorders. In this lesson you will learn more about the definition, classification, and some examples of sulfonamides. Updated: 05/30/2021

What Are Sulfonamides?

Cody arrives at his primary care doctor's office with an earache. After a thorough examination, his doctor states he has an ear infection and wants to prescribe him Bactrim. Cody's doctor then asks if he has ever had an allergic reaction to any sulfonamide medications, and that Bactrim is classified as a sulfonamide antibiotic. Confused by what a sulfonamide is, Cody asks his doctor for more clarification.

Sulfonamides are a synthetic substance created from the sulfonamide chemical group. They are used as a medication to treat a variety of illnesses and conditions. Sulfonamide medications are supplied as oral tablets, oral liquids, or even injections, and require a physician's prescription.

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  • 0:04 What Are Sulfonamides?
  • 0:50 Sulfonamide Classification
  • 2:41 Examples of Sulfonamides
  • 3:26 Lesson Summary
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Sulfonamides Classification

There are generally thought to be two major classifications of sulfonamide medications based upon their chemical structure. Most commonly they're bacteriostatic antibiotic medications, which work by inhibiting bacteria from multiplying, but they don't kill the existing bacteria. Sulfonamides are often combined with trimethoprim, which acts as a bactericidal agent, meaning it kills bacteria.

Other types of sulfonamides do not have antibacterial properties. These can be classified under carbonic anhydrase inhibitors (CAIs), thiazide diuretics, loop diuretics, cyclooxygenase 2 (COX-2) inhibitors, and sulfonylureas.

CA inhibitors are primarily used to treat glaucoma (damage to the optic nerve in the eye) by reducing fluid pressure in the eye. Zonisamide, another sulfonamide, is also considered a CA inhibitor but is used to treat seizures. The exact mechanism of action of zonisamide is not fully understood.

Thiazide diuretics are used to treat hypertension (high blood pressure) and help lower blood pressure by causing diuresis, or increased urination. Similarly, loop diuretics are used to treat hypertension due to heart failure. They also cause diuresis but by a different mechanism than thiazide diuretics.

COX-2 inhibitors are a type of non-steroidal anti-inflammatory medication and are used to treat pain and inflammation by altering the COX-2 enzymes in the body that are responsible for pain and inflammation symptoms.

Finally, sulfonylureas are used to help manage type 2 diabetes. They help lower the blood sugar level in the body by telling the pancreas to release more insulin.

Examples of Sulfonamides

Here are some general examples of sulfonamides:

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Additional Activities

Sulfonamides: Word Scramble Activity

In this activity, you'll check your knowledge regarding the definition, classification, and examples of sulfonamides.


For this activity, study the scrambled letters and unscramble or rearrange the letters to form a word or phrase that fits the given clues. To do this, you must right-click and print this page. With a pencil and an eraser, neatly write your answers in the appropriate blank spaces in the clues.

Scrambled Words



  1. __________ are a group of medicines used to treat a variety of illnesses and conditions, including bacterial infections, high blood pressure, heart failure, etc.
  2. __________ drugs are a type of medication that __________ the growth of bacteria.
  3. Thiazide diuretics help regulate blood pressure by causing increased __________.
  4. COX-2 inhibitors impede the production of COX-2 enzymes, which are the main cause of pain and __________.
  5. Sulfonylureas lower the blood sugar level by increasing the release of __________ from the __________.
  6. Zonisamide is used with other medications to treat and control __________.
  7. CA inhibitors are used to reduce the __________ in the eye.
  8. Loop diuretics can trigger diuresis and are utilized to treat __________ due to heart failure.

Answer Key

  1. Sulfonamides
  2. Bacteriostatic, inhibits
  3. urination
  4. inflammation
  5. insulin, pancreas
  6. seizures
  7. fluid pressure
  8. hypertension

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