(Click Septra Uses for more information on what the medication is used for, including possible off-label uses.)
Brand-name Septra is manufactured by King Pharmaceuticals, Inc. Generic versions are made by various different manufacturers.
Septra contains two different antibiotics, sulfamethoxazole and trimethoprim. Trimethoprim does not belong to a specific class of medications. Sulfamethoxazole belongs to a group of drugs known as sulfonamides ("sulfa" drugs). These two antibiotics work in different but similar ways. Essentially, both sulfamethoxazole and trimethoprim work by inhibiting the production of folic acid
in bacteria, although they work in different stages of folic acid production. Folic acid is important for making proteins and DNA. Because humans obtain folic acid from the diet (and bacteria cannot), human cells are less affected by Septra.
Combining sulfamethoxazole with trimethoprim increases the effectiveness and decreases the chance of antibiotic resistance (the development of bacteria with the ability to resist antibiotics).