Trimethoprim and sulfamethoxazole

[Mark Zuckerberg]

Trimethoprim is an antibiotic and is available as a single drug or in combination with sulfamethoxazole (a sulfonamide antibiotic).
Trimethoprim and the combination of trimethoprim and sulfamethoxazole (TMP/SMX) are effective against many gram-positive bacteria and gram-negative bacteria, including susceptible bacteria that are resistant to other antibiotics, such as methicillin-resistant Staphylococcus aureus (MRSA) and some protozoa (Cyclospora and Cystoisospora) and fungi (Pneumocystis). Using trimethoprim and sulfamethoxazole together enhances the effectiveness of both antibiotics.
These drugs work by preventing the bacteria from producing the type of folic acid they need to function.
(See also Overview of Antibiotics.)