Cefixime, in-vitro activity, pharmacokinetics and tissue penetration

The in-vitro activity of cefixime was studied with clinical isolates and compared with that of other agents. Cefixime exhibited good activity against the Enterobacteriaceae, Haemophilus influenzae, and Neisseria gonorrhoeae, including beta-lactamase producing strains. Activity was also high against Streptococcus pneumoniae and group A and group B beta-haemolytic streptococci. Staphylococcus aureus, faecal streptococci, anaerobic bacteria and Pseudomonas aeruginosa were not susceptible. Activity against susceptible isolates was comparable to cefotaxime and was normally superior to cefuroxime, cephalexin and amoxycillin. The pharmacokinetics of cefixime were studied in six healthy male volunteers, each receiving a 400 mg oral dose following an overnight fast. Tissue penetration of the Antibiotic was estimated with a cantharides-induced blister method. The mean serum elimination half-life was 3.8 h, the mean peak concentration was 3.7 mg/l. Penetration into tissue fluid was rather slow [Tmax 6.7 h) but percentage penetration was high (132.6%). Urinary excretion was low with a 24 h recovery rate of less than 20%, though the concentrations achieved in urine exceeded the MICs of most common urinary tract pathogens for up to 24 h post-dose.