.png | CAS_number = 723-46-6 |ATC_prefix = J01 |ATC_suffix = EC01 |PubChem = 5329 | DrugBank = APRD00076 | C = 10 |H = 11 |N = 3 |O = 3 |S = 1 | molecular_weight = 253.279 g/mol | smiles = CC1=CC(=NO1)NS(=O)(=O)C2=CC=C(C=C2)N | melting_point = 3 | protein_bound = 70% | metabolism = Hepatic acetylation and glucuronidation | elimination_half-life = 10 hours | excretion = Renal | pregnancy_category = C (Au, U.S.)| legal_status = ℞-only (U.S., Ca)| routes_of_administration = Oral}} Sulfamethoxazole is a sulfonamide antibiotic. It is most often used as part of a synergistic combination with trimethoprim in a 5:1 ratio in co-trimoxazole, which is also known as Bactrim or Septrim. It can be used an alternative of amoxicillin-based antibiotics to treat sinusitis.

Mechanism of action

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Sulfonamides are structural anologs and competitive antagonists of para-aminobenzoic acid (PABA). They inhibit normal bacterial utilization of PABA for the synthesis of folic acid, an important metabolite in DNA synthesis. The effects seen are usually bacteriostatic in nature. Folic acid is not synthesized in humans, but is instead a dietary requirement. This allows for the selective toxicicty to bacterial cells (or any cell dependent on synthesizing folic acid) over human cells.

See also

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• trimethoprim

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