Pharmacodynamics of ceftriaxone and cefixime against community-acquired respiratory tract pathogens

Over the last decade or so there has been a growing interest in routes of a ntimicrobial administration other than by the conventional intravenous rout e for institutionalized patients and for some outpatients. Both oral (PO) a nd intramuscular (IM) routes of administration are less costly than giving antimicrobial agents by vein (IV). In addition, fewer complications such as catheter-related sepsis and phlebitis are associated with non-IV routes of administration. Furthermore, a reduced-dosage, reduced-volume TM administr ation of ceftriaxone may provide a tolerable route of administration and eq uivalent bactericidal activities compared with higher dose IV ceftriaxone. The purpose of this study was to determine the time that the drug concentra tion remained in excess of the minimum inhibitory concentration (MIC) (T > MIG) and the duration of bactericidal activities of ceftriaxone one gram ad ministered IV. ceftriaxone 250 mg given IM and cefixime 400 mg given orally against clinical isolates of Streptococcus pneumoniae, Haemophilus influen zae and Moraxella catarrhalis in adult volunteers. Single doses of each age nt were administered and serum concentrations were collected over the stand ard dosing period of 24 h for all study regimens. Ceftriaxone, regardless o f route of administration and dose, resulted in bactericidal activities and T > MIC for 100% of the dosing period for S. pneumoniae, H. influenzae. an d M. catarrhalis. Cefixime maintained at least 50%, T > MIC and bactericida l activity against both isolates each of H. influenzae and M. catarrhalis. Against both isolates of S. pneumoniae cefixime achieved T > MIC for at lea st 50% of the dosing period, but did not maintain bactericidal activity. Re duced dose ceftriaxone given IM seems to be a viable alternative to ceftria xone IV if the pathogen. susceptibility and infection site are known. Based on T > MIC exceeding 50% of the dosing interval, cefixime would be conside red an effective alternative to IV therapy against common respiratory tract pathogens. Clinical studies need to be conducted to confirm these findings . (C) 2001 Published by Elsevier Science B.V. and International Society of Chemotherapy. All rights reserved.