Serum bactericidal activity and kinetics of azlocillin and moxalactam after single and combined administration

Ten healthy volunteers received 5 g azlocillin and 2 g moxalactam iv in single and combined administration. Serum and urine concentrations were measured with bioassay and HPLC (high pressure liquid chromatography), and serum bactericidal activity (SBA) was determined at 1 h and 6 h against 6 different clinical isolates. The combined applications of both antibiotics resulted in minor differences in serum kinetics and urine recovery in comparison to single administration. SBAs of both antibiotics against Enterobacteriaceae were between 1 : 4 and 1 : 8.4 for azlocillin and between 1 : 3 and 1 : 8 for moxalactam after 1 h. The combination of both β-lactam antibiotics did not result in a decrease in SBA against any strain; rather all Enterobacteriaceae showed a slight increase of SBA at 1 h. It can be concluded from these results that combination therapy with azlocillin and moxalactam has no adverse influence on the pharmacokinetics or the bactericidal activity of either substance.