Trimethoprim-sulfamethoxazole: An overview
- D Byron May, PharmD, BCPS
D Byron May, PharmD, BCPS
- Professor and Chairman, Department of Pharmacy Practice
- Campbell University College of Pharmacy & Health Sciences
Trimethoprim-sulfamethoxazole (TMP-SMX), also known as co-trimoxazole, is a combination of two antimicrobial agents that act synergistically against a wide variety of bacteria. Although other combinations of sulfonamides are available with trimethoprim, TMP-SMX is by far the most widely used.
This topic will review basic issues related to the clinical use of trimethoprim-sulfamethoxazole. The multiple clinical settings in which this combination may be used are discussed separately on the appropriate topic reviews.
MECHANISM OF ACTION
The two components, TMP and SMX, work sequentially to inhibit enzyme systems involved in the bacterial synthesis of tetrahydrofolic acid (THF) [1,2].
●SMX is a structural analog of para-aminobenzoic acid (PABA) and competes with PABA to inhibit the synthesis of dihydrofolic acid, an intermediate step in the formation of THF [1,3]. SMX binds to dihydropteroate synthetase which catalyses this reaction .
●TMP binds to bacterial dihydrofolate reductase (in preference to human dihydrofolate reductase), also preventing the formation of THF .
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- MECHANISM OF ACTION
- SPECTRUM OF ACTIVITY
- PHARMACODYNAMICS AND PHARMACOKINETICS
- Metabolism and excretion
- DOSAGE AND ADMINISTRATION
- Renal dose adjustment
- ADVERSE EFFECTS AND PRECAUTIONS
- Adverse effects
- - Life threatening effects
- DRUG INTERACTIONS
- SUMMARY AND RECOMMENDATIONS