NCIt definition : The sulfate salt form of trimethoprim, a synthetic substituted pyrimidine with antibacterial
activity. Trimethoprim sulfate selectively binds to and reversibly inhibits dihydrofolate
reductase, thereby blocking the production of tetrahydrofolic acid from dihydrofolic
acid. This leads to an inhibition of bacterial synthesis of folic acid, thereby affecting
nucleic acid and protein synthesis. Trimethoprim sulfate has a stronger binding affinity
for the bacterial enzyme than for the corresponding mammalian enzyme.;