Absorption: Well absorbed from the GI tract.

Distribution: Widely distributed. Crosses the blood-brain barrier and placenta and enters breast milk.

Protein Binding: TMP: 45%; SMX: 68%.

Metabolism and Excretion: Some metabolism by the liver (20%); remainder excreted unchanged by the kidneys.

Half-life: Trimethoprim—6–11 hr; sulfamethoxazole—9–12 hr, both prolonged in renal failure.

TIME/ACTION PROFILE (blood levels)