Bactrim® (sulfamethoxazole/trimethoprim) is a prescription antibiotic used to treat several infections and to prevent one particular infection, Pneumocystis carinii pneumonia, in people with a weakened immune system.
The drug comes in pill form. Bactrim is taken by mouth, usually twice a day (although it is taken as frequently as four times daily or as infrequently as once daily for certain uses). The pills are available in two strengths:
- Tablets -- 80 mg of trimethoprim and 400 mg of sulfamethoxazole
- DS ("double strength") tablets -- 160 mg of trimethoprim and 800 mg of sulfamethoxazole.
The pills contain two different antibiotics, sulfamethoxazole and trimethoprim. 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. Combining sulfamethoxazole with trimethoprim increases the effectiveness and decreases the chance of antibiotic resistance (when bacteria develop the ability to resist antibiotics).
(Click Bactrim for a more in-depth look at how Bactrim works, potential side effects, general dosing guidelines, and information on what to tell your healthcare provider before using this medication.)