Abstract: Aim The postantibiotic effects(PAEs)induced by Amoxacillin(AMPC)alone or com-bined with gentamicin(GM)or netilmycin(NTL)were studied.Methods The PAEs were determined by the spectrophotometric method.Results The PAEs induced by AM- PC alone to S.aureus and E.faecalis were long;whereas to E.coli, the PAEs were poor.PAEs induced by GM or NTL alone to Gram-positive cocci were longer than to Gram-negative bacilli.The PAEs of NTL were more obvious than those of GM.The PAEs of AMPC combined with 4x MIC of GM or NTL were all synergic or additive, and the combined PAEs to Gram-positive cocci were longer than to Gram-negative bacilli.The combined PAEs of AMPC plus NTL were more obvious than plus GM.Conclusion It is suggested that the rational prelonged dosing intervals in combinations of AMPC with two aminoglycosides should be recommended.

Key words: amoxacillin, gentamicin, netilmicin, PAE