Intravenous pharmacokinetics and in vitro bactericidal activity of trimethoprim-sulfamethoxazole.

Trimethoprim-sulfamethoxazole (240 mg of trimethoprim plus 1,200 mg of sulfamethoxazole) was administered intravenously in a volume of 200 ml to 7 volunteers every 12 hr for 4 days. The mean peak levels of TMP and SMZ in plasma were 3.22 and 100 micrograms/ml, respectively, on day 1 and 5.91 and 178 micrograms/ml, respectively, on day 4, when a steady state was achieved. Tests of in vitro susceptibility indicated that these concentrations are bactericidal for a large proportion of enteric gram-negative bacilli.