Sulfamethoxazole

• 4-amino- N-(5 -methyl- 1,2- oxazol- 3-yl) benzenesulfonamide
• N1 -(5- methyl-3- isoxazolyl) sulfanilamide
• 3 - (p- Aminophenylsulfonamido ) - 5 -methylisoxazole
• Abacin

J01EC01

Crystalline solid

Sulfonamides

Fixed

167 ° C.

5.6

Slightly soluble in water ( 0.61 g · l-1 at 37 ° C)

Attention

2300 mg · kg -1 ( LD50, mouse, oral)

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Sulfamethoxazole is an antibiotic from the group of sulfonamides, which is mainly used in the control of urinary tract infections and pneumonia.

In Germany sulfamethoxazole is only available in fixed combination with trimethoprim as a finished product. This fixed combination in the ratio 5:1 is also called co-trimoxazole.

Specific indications include combating Pneumocystis jirovecii (formerly Pneumocystis carinii ), Nocardia asteroides and Stenotrophomonas maltophilia.

Mechanism of Action

Sulfamethoxazole is a competitive antagonist of the dihydropteroate synthase. The natural substrate of this enzyme is para- aminobenzoic acid ( PABA). Thus inhibited the enzyme reaction is an essential step of the bacterial folic acid synthesis. Folic acid is required for the synthesis of DNA. People does not affect this inhibition, since these can not synthesize folic acid itself, but obtained from the diet.

Pharmacokinetics

Sulfamethoxazole has a plasma half -life of nine to eleven hours.

Side effects

The side effects of sulfamethoxazole correspond to those of the sulfonamides, where skin problems occur most frequently. Skin reactions of various kinds, most eruptions are observed at 2-3 percent of those treated. Dangerous blood counts are concerned side effects that can affect all cell lines: leukopenia, anemia, and thrombocytopenia are possible. By side effects on the central nervous system can lead to convulsions and ataxia, psychoses and depression. More common are nausea and vomiting, loss of appetite and diarrhea. Liver involvement may for transaminases and renal involvement lead to increased creatinine.

In the conventional combination with trimethoprim sulfamethoxazole can cause the heart to prolongation of the QT interval and should therefore not be used in patients with a longQT syndrome.

Contraindications

The combination of sulfamethoxazole and trimethoprim may not except in case of hypersensitivity to the ingredients even in erythema multiforme, pre-existing blood dyscrasias, glucose -6- phosphate dehydrogenase deficiency, severe renal insufficiency, severe hepatic impairment, porphyria, premature infants and neonates with hyperbilirubinemia be applied. In mild renal and hepatic dysfunction, thyroid dysfunction and newborns aged under five weeks, they should only be used in exceptional cases, with careful monitoring.

Trade names

Bactrim (A, CH), Drylin (D), Escoprim (CH), Eusaprim (D, A), Kepinol (D), Lagatrim (CH), Nopil (CH), TMS forte (D ), numerous generics (D, A, CH)