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Other information

Indication
For the treatment of bronchitis, prostatitis and urinary tract infections

Pharmacology
Sulfamethoxazole is a sulfonamide drug that inhibits bacterial synthesis of dihydrofolic acid by competing with para-aminobenzoic acid (PABA). Sulfamethoxazole is normally given in combination with Trimethoprim (a dihydrofolate reductase inhibitor). Studies have shown that bacterial resistance develops more slowly with the combination of the two drugs than with either Trimethoprim or Sulfamethoxazole alone.

Mechanism Of Action
Sulfonamides inhibit bacterial dihydrofolate synthetase, causing interference in the conversion of p-aminobenzoic acid (PABA) into folic acid. As folic acid is a coenzyme responsible for the transport of one-carbon fragments from one molecule to another, it is an essential component of bacterial development. Pyrimethamine and trimethoprim inhibit dihydrofolate reductase, the immediate next step, and therefore act synergistically with the sulfonamides.

Drug Category
Anti-Infectives; Sulfonamides; ATC:J01EC01

Brand Names/Synonyms
A047; Apo-Sulfamethoxazole; Azo Gantanol; Azo-Gantanol; Bactrim; Bactrim Ds; Bactrim Pediatric; Bactrimel; Co-Trimoxazole; Cotrim; Cotrim D.S.; Eusaprim; Fectrim; Gamazole; Gantanol; Gantanol-Ds; MS 53; Metoxal; Radonil; SIM; Septra; Septra Ds; Septra Grape; Septran; Septrin; Simsinomin; Sinomin; Sulfamethalazole; Sulfamethoprim; Sulfamethoprim-Ds; Sulfamethoxazol; Sulfamethoxazole; Sulfamethoxazole & Trimethoprim; Sulfamethoxazole Trimethoprim; Sulfamethoxizole; Sulfamethylisoxazole; Sulfatrim; Sulfatrim Pediatric; Sulfatrim-Ds; Sulfatrim-Ss; Sulfisomezole; Sulmeprim; Sulmeprim Pediatric; Sulpha-Methoxizole; Sulphamethalazole; Sulphamethoxazol; Sulphamethoxazole; Sulphamethoxazole Bp 98; Sulphamethylisoxazole; Sulphisomezole; Trib; Trimeth/Sulfa; Trimetoprim-Sulfa; Urobak; Uroplus Ds; Uroplus Ss

Dosage Forms
TABLET

Absorption
Sulfamethoxazole is rapidly absorbed following oral administration.

Interactions
Interactions for Sulfamethoxazole:

In elderly patients concurrently receiving certain diuretics, primarily thiazides, an increased incidence of thrombopenia with purpura has been reported.

It has been reported that sulfamethoxazole may prolong the prothrombin time in patients who are receiving the anticoagulant warfarin. This interaction should be kept in mind when Gantanol is given to patients already on anticoagulant therapy, and the coagulation time should be reassessed.

Sulfamethoxazole may inhibit the hepatic metabolism of phenytoin. At a 1.6-g dose, sulfamethoxazole produced a slight but significant increase in the half-life of phenytoin but did not produce a corresponding decrease in the metabolic clearance rate. When administering these drugs concurrently, one should be alert for possible excessive phenytoin effect.

Sulfonamides can also displace methotrexate from plasma protein-binding sites, thus increasing free methotrexate concentrations.

The presence of sulfamethoxazole may interfere with the Jaffé alkaline picrate reaction assay for creatinine, resulting in overestimations of about 10% in the range of normal values.

Chemical IUPAC Name
4-amino-N-(5-methyloxazol-3-yl)-benzenesulfonamide

Chemical Formula
C10H11N3O3S

Half Life
Not Available

Drug Type
Approved Drug

# Accession No
APRD00076

CAS Registry Number
723-46-6