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Sulfamethoxazole
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| Systematic (IUPAC) name | |
| 4-amino-N-(5-methylisoxazol-3-yl)-benzenesulfonamide | |
| Identifiers | |
| CAS number | |
| ATC code | J01 |
| PubChem | |
| DrugBank | |
| Chemical data | |
| Formula | C10H11N3O3S |
| Mol. mass | 253.279 g/mol |
| SMILES | & |
| 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. | |
| Legal status |
Prescription Only (S4)(AU) ℞-only |
| Routes | Oral |
Sulfamethoxazole 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, which is also known as Bactrim, Septrin, or Septra (also abbreviated SMX/TMP). 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.
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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.[1] 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 do the drugs from binding and blocking folic acid synthesis.
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.
Gardnerella
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.
References
- ^ Martindale, The extra pharmacopoeia, 30th ed, p. 208
External links
See also
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Wikipedia content modification information:
- This page was last modified on 18 September 2008, at 00:11.
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