Previous Article | Next Article ![]()
Antimicrobial Agents and Chemotherapy, November 1998, p. 2841-2847, Vol. 42, No. 11
Department of Pharmacokinetics, Centre of
Science & Technology LekBioTech, Moscow 117246, Russia,1 and
Division of Infectious Diseases, Roger Williams Medical Center,
Rhode Island Hospital, Brown University, Providence, Rhode
Island2
Received 30 January 1998/Returned for modification 19 May
1998/Accepted 10 August 1998
Time-kill studies, even those performed with in vitro dynamic
models, often do not provide definitive comparisons of different antimicrobial agents. Also, they do not allow determinations of equiefficient doses or predictions of area under the
concentration-time curve (AUC)/MIC breakpoints that might be related to
antimicrobial effects (AMEs). In the present study, a wide range of
single doses of trovafloxacin (TR) and twice-daily doses of
ciprofloxacin (CI) were mimicked in an in vitro dynamic model. The AMEs
of TR and CI against gram-negative bacteria with similar
susceptibilities to both drugs were related to AUC/MICs that varied
over similar eight-fold ranges [from 54 to 432 and from 59 to 473 (µg · h/ml)/(µg/ml), respectively]. The observation periods
were designed to include complete bacterial regrowth, and the AME was
expressed by its intensity (the area between the control growth in the
absence of antibiotics and the antibiotic-induced time-kill and
regrowth curves up to the point where viable counts of regrowing
bacteria equal those achieved in the absence of drug
[IE]). In each experiment monoexponential
pharmacokinetic profiles of TR and CI were simulated with
half-lives of 9.2 and 4.0 h, respectively. Linear
relationships between IE and log AUC/MIC were
established for TR and CI against three bacteria: Escherichia
coli (MIC of TR [MICTR] = 0.25 µg/ml; MIC of CI
[MICCI] = 0.12 µg/ml), Pseudomonas
aeruginosa (MICTR = 0.3 µg/ml; MICCI = 0.15 µg/ml), and Klebsiella pneumoniae
(MICTR = 0.25 µg/ml; MICCI = 0.12 µg/ml). The slopes and intercepts of these relationships differed for
TR and CI, and the IE-log AUC/MIC plots were
not superimposed, although they were similar for all bacteria with a
given antibiotic. By using the relationships between IE and log AUC/MIC, TR was more efficient than
CI. The predicted value of the AUC/MIC breakpoint for TR [mean for all
three bacteria, 63 (µg · h/ml)/(µg/ml)] was approximately
twofold lower than that for CI. Based on the
IE-log AUC/MIC relationships, the respective dose (D)-response relationships were reconstructed.
Like the IE-log AUC/MIC relationships, the
IE-log D plots showed TR to be more efficient than CI. Single doses of TR that are as efficient as two
500-mg doses of CI (500 mg given every 12 h) were similar for the
three strains (199, 226, and 203 mg). This study suggests that in vitro
evaluation of the relationships between IE and
AUC/MIC or D might be a reliable basis for comparing
different fluoroquinolones and that the results of such comparative
studies may be highly dependent on their experimental design and datum quantitation.
0066-4804/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
A New Approach to In Vitro Comparisons of Antibiotics in Dynamic
Models: Equivalent Area under the Curve/MIC Breakpoints and
Equiefficient Doses of Trovafloxacin and Ciprofloxacin against
Bacteria of Similar Susceptibilities
*
Corresponding author. Mailing address: Department of
Pharmacokinetics, Centre of Science & Technology LekBioTech,
8 Nauchny proezd, Moscow 117246, Russia. Phone: 7 (095) 332-3435. Fax:
7 (095) 331-0101. E-mail: Biotec{at}glas.apc.org.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»