Trimethoprim and sulfamethoxazole (TMP/SMX)

Definition

Trimethoprim and sulfamethoxazole (TMP/SMX) is a combination antibiotic used to treat various bacterial infections, including urinary tract infections (UTIs). It works by inhibiting two sequential steps in the bacterial folate synthesis pathway, making it highly effective against a broad spectrum of bacteria.

5 Must Know Facts For Your Next Test

1. TMP/SMX is commonly prescribed for UTIs due to its effectiveness against E. coli, the most frequent cause of these infections.
2. It is a synergistic combination where trimethoprim inhibits dihydrofolate reductase and sulfamethoxazole inhibits dihydropteroate synthase.
3. Common side effects include gastrointestinal upset, rash, and in rare cases, Stevens-Johnson syndrome.
4. Patients with a known sulfa allergy should not take TMP/SMX due to the risk of severe allergic reactions.
5. Resistance to TMP/SMX can occur, so it should be used based on susceptibility testing when possible.

Review Questions

• What are the primary mechanisms through which TMP/SMX exerts its antibacterial effects?
• Why should TMP/SMX be avoided in patients with sulfa allergies?
• What are common side effects associated with TMP/SMX?

Related terms

Urinary Tract Infection (UTI): An infection in any part of the urinary system, most commonly caused by bacteria like E. coli.

Antibiotic Resistance: The ability of bacteria to withstand the effects of an antibiotic that they were once sensitive to.

Folate Synthesis Pathway: A series of biochemical processes that produce folic acid derivatives crucial for bacterial DNA synthesis.