All of the following are topically used sulfonamides EXCEPT:
💡 Explanation
## Core Concept
Topically used sulfonamides are primarily employed in the treatment of ocular infections and as antimicrobial agents in dermatology. These agents leverage the bacteriostatic properties of sulfonamides to inhibit folic acid synthesis in bacteria. The question requires identification of a sulfonamide not used topically.
## Why the Correct Answer is Right
Mafenide acetate is known for its use in burn creams to prevent infection of severe burns. It has significant systemic absorption and can cause metabolic acidosis. Sulfacetamide is commonly used in eye drops and ointments for the treatment of bacterial conjunctivitis. Silver sulfadiazine, another topical agent, is used for its antimicrobial properties in burn creams. However, **trimethoprim-sulfonamide combinations** are generally used orally or intravenously, not topically, for their synergistic effect on the folate pathway in bacteria.
## Why Each Wrong Option is Incorrect
* **Option A:** Mafenide acetate is indeed used topically, particularly in burn patients to prevent infection.
* **Option B:** Sulfacetamide is used topically, especially in ophthalmology for treating conjunctivitis.
* **Option D:** Silver sulfadiazine is a topical cream used on burns for its antimicrobial properties.
## Clinical Pearl / High-Yield Fact
A key point to remember is that while sulfonamides have a broad range of applications, their use can be limited by side effects and resistance. Topical sulfonamides are particularly useful for localized infections, reducing systemic side effects.