Cefixime is an orally absorbed third generation cephalosporin with a broad spectrum of activity against Gram-positive and Gram-negative bacteria and is highly resistant to beta-lactamase degradation. In general serum and urinary concentrations of cefixime achieved after recommended daily doses are well above the minimal inhibitory concentrations at 90% for indicated microorganisms. The pharmacokinetics of cefixime were determined in adult and pediatric subjects. In general the half-life of the drug is about 3 to 4 hours and is not dependent on dose. The drug is not extensively bound to serum proteins; the free fraction is about 31% and is concentration-independent. The absolute bioavailability, based on comparisons of area under the serum concentration-time curve values after 200-mg intravenous, 200-mg oral solution, and 200- and 400-mg capsule doses, ranged from 40 to 52%, showing a comparable bioavailability for cefixime at single 200- and 400-mg oral doses. In a dose proportionality study, over an oral dose range of 200 to 2000 mg, peak serum concentration (Cmax) and area under the concentration-time values increased linearly but were not directly proportional with dose. Upon multiple dosing for 2 weeks on a 400-mg daily or 200-mg twice a day regimen, serum concentrations and urinary recovery of unchanged drug were similar for each group, and there was no drug accumulation. Peak serum concentration and area under the concentration-time curve values after a 400-mg dose were almost double those after a 200-mg dose. All formulations of cefixime were bioequivalent to an oral reference solution at doses of 200 and 400 mg.(ABSTRACT TRUNCATED AT 250 WORDS)