Sulfamethoxazole is an oral sulfonamide antibiotic, given in combination with trimethoprim, used to treat a variety of infections of the urinary tract, respiratory system, and gastrointestinal tract. Sulfamethoxazole is a bacteriostatic sulfonamide antibiotic that interferes with folic acid synthesis in susceptible bacteria.
- Mechanism
- Curator reviewed · 5 references
Sulfamethoxazole is a sulfonamide that inhibits bacterial dihydrofolic acid synthesis due to its structural similarity to an endogenous substrate, para-aminobenzoic acid (PABA). Most bacteria meet their need for folic acid by synthesizing it from PABA, as opposed to Animalia that require exogenous folic acid sources. Sulfamethoxazole competitively inhibits dihydropteroate synthase, the enzyme responsible for bacterial conversion of PABA to dihydrofolic acid. Inhibition of this pathway prevents the synthesis of tetrahydrofolate and, ultimately, the synthesis of bacterial purines and DNA, resulting in a bacteriostatic effect.
- Primary indication
- Sulfamethoxazole is indicated in combination with trimethoprim, in various formulations, for the following infections caused by bacteria with documented susceptibility: urinary tract infections, acute otitis media in pediatric patients (when clinically indicated), acute exacerbations of...Curator reviewed · 13 structured indications
- Formula / weight
- C10H11N3O3S · 253.278 g/mol (avg)
- First approval
- Canada, 2000 · United States, 1973
- Also known as
- Sulphamethoxazole
- Code names
- NSC-147832 · RO 4-2130 · STX-608
- Brand names
Resolves to
JLKIGFTWXXRPMT-UHFFFAOYSA-NSMILESCC1=CC(NS(=O)(=O)C2=CC=C(N)C=C2)=NO1What you can answer from here — as of September 23, 2026
Which drugs share a target with Sulfamethoxazole, and which of those have an active Phase 3 trial?
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