title: Dose optimization of voriconazole/anidulafungin combination against Aspergillus fumigatus using an in vitro pharmacokinetic/pharmacodynamic model and response surface analysis: clinical implications for azole-resistant aspergillosis.
abstract: Combination therapy of voriconazole with an echinocandin is often employed in order to increase the efficacy of voriconazole monotherapy.
  
  
  
  Four clinical Aspergillus fumigatus isolates with different in vitro susceptibilities to voriconazole (MIC 0.125-2 mg/L) and anidulafungin (MEC 0.008-0.016 mg/L) were tested in an in vitro pharmacokinetic/pharmacodynamic model simulating human serum concentrations of standard dosages of voriconazole and anidulafungin. Fungal growth was assessed using galactomannan production and quantitative PCR. Drug concentrations were determined with bioassays. Pharmacodynamic interactions were assessed using Bliss independence analysis (BI) and Loewe additivity-based canonical mixture response-surface non-linear regression analysis (LA). Probability of target attainment (PTA) was estimated with Monte Carlo analysis for different doses of anidulafungin (25, 50 and 100 mg) and azole resistance rates (5%-25%).
  
  
  
  Synergy [BI 51% (8%-80%), LA 0.63 (0.38-0.79)] was found at low anidulafungin (fCmax/MEC <10) and voriconazole (fAUC/MIC <10) exposures, whereas antagonism [BI 12% (5%-18%, LA 1.12 (1.04-4.6)] was found at higher drug exposures. The largest increase in PTA was found with 25 mg of anidulafungin and voriconazole MIC distributions with high (>10%) resistance rates. PTAs for isolates with voriconazole MICs of 1, 2 and 4 mg/L was 78%, 12% and 0% with voriconazole monotherapy and 96%-100%, 68%-82% and 9%-20% with combination therapy, respectively. Optimal activity was associated with a voriconazole tCmin/MIC ratio of 1.5 for monotherapy and 0.75 for combination therapy.
  
  
  
  The present study indicated that the combination of voriconazole with low-dose anidulafungin may increase the efficacy and reduce the cost and potential toxicity of antifungal therapy, particularly against azole-resistant A. fumigatus isolates and in patients with subtherapeutic serum levels. This hypothesis warrants further in vivo verification.
authors: Clinical Microbiology Laboratory, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece.
authors: Maria
authors: M
authors: Siopi
authors: Clinical Microbiology Laboratory, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece.
authors: Nikolaos
authors: N
authors: Siafakas
authors: Clinical Microbiology Laboratory, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece.
authors: Sophia
authors: S
authors: Vourli
authors: Department of Medical Microbiology and Infectious Diseases, Erasmus Medical Center, Rotterdam, The Netherlands.
authors: Johan W
authors: JW
authors: Mouton
authors: Clinical Microbiology Laboratory, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece.
authors: Loukia
authors: L
authors: Zerva
authors: Clinical Microbiology Laboratory, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece jmeletiadis@med.uoa.gr.|Department of Medical Microbiology and Infectious Diseases, Erasmus Medical Center, Rotterdam, The Netherlands.
authors: Joseph
authors: J
authors: Meletiadis
mesh_terms: D000077612:Anidulafungin; D000935:Antifungal Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000494:pharmacology; D001228:Aspergillosis / Q000188:drug therapy*; D001232:Aspergillus fumigatus / Q000187:drug effects*; D004271:DNA, Fungal / Q000032:analysis; D004359:Drug Therapy, Combination / Q000379:methods; D054714:Echinocandins / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000494:pharmacology; D005690:Galactose / Q000031:analogs & derivatives; D006801:Humans; D008351:Mannans / Q000032:analysis; D008826:Microbial Sensitivity Tests; D008962:Models, Theoretical; D009010:Monte Carlo Method; D060888:Real-Time Polymerase Chain Reaction; D065819:Voriconazole / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000494:pharmacology
chemical_list: D000935:Antifungal Agents; D004271:DNA, Fungal; D054714:Echinocandins; D008351:Mannans; C012990:galactomannan; D000077612:Anidulafungin; D065819:Voriconazole; D005690:Galactose