General description

Chemical structure: pyrimidine

Application

Trimethoprim is primarily used as an antibacterial agent. It has dihydrofolate reductase inhibitor activity with selectivity for the prokaryote enzyme. It is used clinically to treat urinary tract infections, mild acute prostatitis, recurrent cystitis, asymptomatic bacteriuria during pregnancy and respiratory tract infections. Trimethoprim lactate salt is used as a selection agent.

Biochem/physiol Actions

The combination of trimethoprim and sulfamethoxazole interferes with the cellular metabolism of folic acid in the bacterial cell by blocking the biosynthesis of nucleotides. Trimethoprim binds to prokaryote-specific dihydrofolate reductase (DHFR) and inhibits the reduction of dihydrofolic acid (DHF) to tetrahydrofolic acid (THF). THF is an essential precursor in the thymidine synthesis pathway and interference with this pathway inhibits bacterial DNA synthesis.