title: Pharmacokinetic considerations and efficacy of levofloxacin in an inhalational anthrax (postexposure) rhesus monkey model.
abstract: Because the treatment of inhalational anthrax cannot be studied in human clinical trials, it is necessary to conduct efficacy studies using a rhesus monkey model. However, the half-life of levofloxacin was approximately three times shorter in rhesus monkeys than in humans. Computer simulations to match plasma concentration profile, area under the concentration-time curve (AUC), and time above MIC for a human oral dose of 500 mg levofloxacin once a day identified a dosing regimen in rhesus monkeys that would most closely match human exposure: 15 mg/kg followed by 4 mg/kg administered 12 h later. Approximately 24 h following inhalational exposure to approximately 49 times the 50% lethal doses of Bacillus anthracis (Ames strain), monkeys were treated daily with vehicle, levofloxacin, or ciprofloxacin for 30 days. Ciprofloxacin was administered at 16 mg/kg twice a day. Following the 30-day treatment, monkeys were observed for 70 days. Nine of 10 control monkeys died within 9 days of exposure. No clinical signs were observed in fluoroquinolone-treated monkeys during the 30 treatment days. One monkey died 8 days after levofloxacin treatment, and two monkeys from the ciprofloxacin group died 27 and 36 days posttreatment, respectively. These deaths were probably related to the germination of residual spores. B. anthracis was positively cultured from several tissues from the three fluoroquinolone-treated monkeys that died. MICs of levofloxacin and ciprofloxacin from these cultures were comparable to those from the inoculating strain. These data demonstrate that a humanized dosing regimen of levofloxacin was effective in preventing morbidity and mortality from inhalational anthrax in rhesus monkeys and did not select for resistance.
authors.affiliation: Johnson & Johnson Pharmaceutical Research and Development, LLC, 1000 Route 202 South, Raritan, NJ 08869, USA. mkao@prdus.jnj.com
authors.forename: L Mark
authors.initials: LM
authors.lastname: Kao
authors.forename: Karen
authors.initials: K
authors.lastname: Bush
authors.forename: Roy
authors.initials: R
authors.lastname: Barnewall
authors.forename: James
authors.initials: J
authors.lastname: Estep
authors.forename: Frederic W
authors.initials: FW
authors.lastname: Thalacker
authors.forename: Pamela H
authors.initials: PH
authors.lastname: Olson
authors.forename: George L
authors.initials: GL
authors.lastname: Drusano
authors.forename: Neil
authors.initials: N
authors.lastname: Minton
authors.forename: Shuchean
authors.initials: S
authors.lastname: Chien
authors.forename: Alex
authors.initials: A
authors.lastname: Hemeryck
authors.forename: Michael F
authors.initials: MF
authors.lastname: Kelley
mesh_terms: D000336:Aerosols; D000818:Animals; D000881:Anthrax / Q000188:drug therapy* / Q000401:mortality / Q000473:pathology; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D019540:Area Under Curve; D001408:Bacillus anthracis / Q000187:drug effects; D003198:Computer Simulation; D004305:Dose-Response Relationship, Drug; D004339:Drug Compounding; D005260:Female; D006801:Humans; D019570:Inhalation Exposure; D064704:Levofloxacin; D008253:Macaca mulatta; D008297:Male; D008826:Microbial Sensitivity Tests; D015242:Ofloxacin / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D013171:Spores, Bacterial / Q000187:drug effects
chemical_list: D000336:Aerosols; D000900:Anti-Bacterial Agents; D064704:Levofloxacin; D015242:Ofloxacin