Introduction

Trimethoprim is an antibiotic, mainly used in the management of urinary tract infections.

Mechanism of action

Mechanism of action
  • Interferes with DNA synthesis by inhibiting dihydrofolate reductase

Adverse effects

  • Myelosuppression
  • Transient rise in creatinine: trimethoprim competitively inhibits the tubular secretion of creatinine resulting in a temporary increase which reverses upon stopping the drug*


*Trimethoprim blocks the ENaC channel in the distal nephron, causing a hyperkalaemic distal RTA (type 4). It also inhibits creatinine secretion, often leading to an increase in creatinine by around 40 points (but not necessarily causing AKI).