Article: Sulfamethoxazole

Sulfamethoxazole
Systematic (IUPAC) name
4-amino-N-(5-methylisoxazol-3-yl)-benzenesulfonamide
Identifiers
CAS number	723-46-6
ATC code	J01EC01
PubChem	5329
DrugBank	APRD00076
Chemical data
Formula	C10H11N3O3S
Mol. weight	253.279 g/mol
SMILES	CC1=CC(=NO1)NS(=O)(=O)C2=CC=C(C=C2)N
Physical data
Melt. point	3°C (37°F)
Pharmacokinetic data
Bioavailability	?
Protein binding	70%
Metabolism	Hepatic acetylation and glucuronidation
Half life	10 hours
Excretion	Renal
Therapeutic considerations
Pregnancy cat.	C (Au, U.S.)
Legal status	℞-only (U.S., Ca)
Routes	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 Bactrin or Septrin. It can be used as an alternative to amoxicillin-based antibiotics to treat sinusitis.

Mechanism of action

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

• trimethoprim

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