Trimethoprim is a classic example of what kind of agent?

Trimethoprim is a classic example of what kind of agent?

• A. Sulfonamide
• B. Nucleic Acid Synthesis Inhibitor
• C. Cell Wall Inhibitor
• D. Folic Acid Analog

Answer: (D)

Trimethoprim is a folic acid analog, an antifolate. It targets bacterial folate metabolism by inhibiting dihydrofolate reductase, which prevents the conversion of dihydrofolate to tetrahydrofolate. Without tetrahydrofolate, the synthesis of thymidine and purines stalls, so DNA replication slows or stops and bacterial growth is impeded. This specific action makes it classifiable as a folic acid analog rather than a general nucleic acid synthesis inhibitor. In practice, it’s often paired with a sulfonamide to block sequential steps in the same pathway—sulfonamides inhibit dihydropteroate synthase, while trimethoprim blocks dihydrofolate reductase, producing a synergistic effect. It’s not a cell wall inhibitor, and its defining feature is its antifolate mechanism via folate analog activity.

Trimethoprim is a folic acid analog, an antifolate. It targets bacterial folate metabolism by inhibiting dihydrofolate reductase, which prevents the conversion of dihydrofolate to tetrahydrofolate. Without tetrahydrofolate, the synthesis of thymidine and purines stalls, so DNA replication slows or stops and bacterial growth is impeded. This specific action makes it classifiable as a folic acid analog rather than a general nucleic acid synthesis inhibitor. In practice, it’s often paired with a sulfonamide to block sequential steps in the same pathway—sulfonamides inhibit dihydropteroate synthase, while trimethoprim blocks dihydrofolate reductase, producing a synergistic effect. It’s not a cell wall inhibitor, and its defining feature is its antifolate mechanism via folate analog activity.