Sulfamethoxazole: Wikis


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From Wikipedia, the free encyclopedia

Systematic (IUPAC) name
CAS number 723-46-6
ATC code J01EC01 QJ01EQ11
PubChem 5329
DrugBank APRD00076
ChemSpider 5138
Chemical data
Formula C 10H11N3O3S 
Mol. mass 253.279 g/mol
SMILES eMolecules & PubChem
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 Prescription Only (S4) (AU) ℞-only
Routes Oral
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Sulfamethoxazole (abbreviated SMX[1][2] and less reliably[3] SMZ[4][5][6]) is a sulfonamide bacteriostatic antibiotic. It is most often used as part of a synergistic combination with trimethoprim in a 5:1 ratio in co-trimoxazole (abbreviated SXT, SMX-TMP and SMZ-TMP,[7] or TMP-SMX and TMP-SMZ), also known under trade names such as Bactrim, Septrin, or Septra. Its primary activity is against susceptible forms of Streptococcus, Staphylococcus aureus, Escherichia coli, Haemophilus influenzae, and oral anaerobes. It is commonly used to treat urinary tract infections. In addition can be used as an alternative to amoxicillin-based antibiotics to treat sinusitis. It can also be used to treat toxoplasmosis.

Other names include: sulfamethylisoxazol, sulfisomezole, MS 53, RO 4 2130,[8][1][2] and sulfamethazole.[9]


Mechanism of action

Sulfonamides are structural analogs 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.[10] 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 toxicity to bacterial cells (or any cell dependent on synthesizing folic acid) over human cells. Bacterial resistance to sulfamethoxazole are caused by mutations in the folic acid enzyme that inhibit PABA from binding and block folic acid synthesis.

Tetrahydrofolate synthesis pathway

Side effects

The most common side effect of sulfamethoxazole/trimethoprim is gastrointestinal upset. Allergies to sulfa-based medications typically cause skin rashes, hives, or trouble breathing or swallowing and warrant immediate discontinuation of the medication and contact with doctor immediately. Sulfamethoxazole/trimethoprim is also known to increase blood concentrations of the drug warfarin (U.S. brand name: Coumadin) and can cause an unexpected increase in clotting time and uncontrolled bleeding. Neutropenia and thrombocytopenia also are rare adverse effects to be monitored if a patient is placed on long-term therapy.


A TM-SXT (or simply SXT) disk impregnated with trimethoprim and sulfamethoxazole may be used to help identify an organism as Gardnerella vaginalis; it is sensitive to the TM-SXT disk. Sulfamethoxazole can also cause nausea, severe stomach or abdomen pains. Headaches commonly occur when taking sulfamethoxazole. Muscle pains sometimes occur when taking this medicine. If symptoms persist or you have trouble breathing or you have swelling of the face, mouth or tongue discontinue medicine or get emergency medical help for swelling of the face, mouth or tongue. These are often symptoms of a severe allergic reaction.

See also


  1. ^ a b PubChem, "Sulfamethoxazole - Substance Summary"
  2. ^ a b ChemDB, "Sulfamethoxazole"
  3. ^ "SMZ" is not found in databases, but often seen in the published literature; it could however be confused with sulfamethazine, also seen abbreviated SMZ.
  4. ^ Ma, M.; Cheng, Y.; Xu, Z.; Xu, P.; Qu, H.; Fang, Y.; Xu, T.; Wen, L. (2007). "Evaluation of polyamidoamine (PAMAM) dendrimers as drug carriers of anti-bacterial drugs using sulfamethoxazole (SMZ) as a model drug". European journal of medicinal chemistry 42 (1): 93–8. doi:10.1016/j.ejmech.2006.07.015. PMID 17095123.  
  5. ^ Garg, S.K.; Ghosh, S.S.; Mathur, V.S. (1986). "Comparative pharmacokinetic study of four different sulfonamides in combination with trimethoprim in human volunteers". International journal of clinical pharmacology, therapy, and toxicology 24 (1): 23–5. PMID 3485584.  
  6. ^ SMZ in Abstract of "Rat model of concurrent Pneumocystis carinii (Pc), Toxoplasma gondii (Tg), and Mycobacterium avium complex (MAC) infections for assessment of multiple prophylaxis" at
  7. ^ SMZ-TMP in Abstract of "Cutaneous hypersensitivity to sulfamethoxazole-trimethoprim (SMZ TMP) in HIV infected patients" at
  8. ^ BIAM, "Sulfamethoxazole"
  9. ^ Sulfamethazole in "Clinical Diabetes: Case Study: A 90-Year-Old Man With Confusion and Night Sweats", and "Chronic Granulomatous Disease"
  10. ^ Martindale, The extra pharmacopoeia, 30th ed, p. 208


External links

you use this antibiotic for MRSA

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