Bactrim is a prescription medication used for treating various types of bacterial infections. It can also be used to prevent Pneumocystis carinii pneumonia in people with a weakened immune system. The combination drug contains two different antibiotics that work by inhibiting the production of folic acid in bacteria. Bactrim comes in tablet form and is usually taken twice a day.
What Is Bactrim?
Bactrim® (sulfamethoxazole/trimethoprim) is a prescription antibiotic approved to treat a variety of different infections. In addition to treating infections, it is also approved to prevent one particular infection, Pneumocystis cariniipneumonia, in people with a weakened immune system.
(Click Bactrim Uses for more information on what the medication is used for, including possible off-label uses.)
Who Makes It?
Brand-name Bactrim is manufactured by Mutual Pharmaceutical Company, Inc. and is marketed and distributed by AR Scientific. Generic versions are made by various different manufacturers.
How Does It Work?
Bactrim contains two different antibiotics, sulfamethoxazole and trimethoprim. Sulfamethoxazole belongs to a group of drugs known as sulfonamides ("sulfa" drugs). Trimethoprim does not belong to a specific class of medications. 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 Bactrim.
Combining sulfamethoxazole with trimethoprim increases the effectiveness and decreases the chance of antibiotic resistance (when bacteria develop the ability to resist antibiotics).
Written by/reviewed by: Kristi Monson, PharmD;Arthur Schoenstadt, MD
Last reviewed by: KristiMonson, PharmD;
List of references (click here):
Bactrim [package insert]. Philadelphia, PA: AR Scientific, Inc.;2013 June.
Food and Drug Administration, Center for Drug Evaluation and Research. Electronic orange book: approved drug products with therapeutic equivalence evaluations. FDA Web site. Available at: http://www.fda.gov/cder/ob/. Accessed September 3, 2008.
Briggs GG, Freeman RK, Yaffe SJ. Drugs in Pregnancy and Lactation. 7th ed. Philadelphia (PA): Lippincott Williams & Wilkins;2005.
National Library of Medicine (US). Drugs and Lactation Database (LactMED). NLM Web site. Available at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT. Accessed August 19, 2008.
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