In Vitro Elution Studies of Amikacin and Cefazolin from Polymethylmethacrylate

Authors

  • HEIDI PHILLIPS VMD, Diplomate ACVS,

    1. Allegheny Veterinary Emergency Trauma and Specialty, Monroeville, PA
    2. Clinical Pharmacology Laboratory, Auburn University, College of Veterinary Medicine, Auburn, AL
    3. Matthew J. Ryan Veterinary Hospital of the University of Pennsylvania, Philadelphia, PA
    4. Bay Area Veterinary Specialists, San Leandro, CA
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  • DAWN M. BOOTHE DVM, PhD, Diplomate ACVIM, ACVCP,

    1. Allegheny Veterinary Emergency Trauma and Specialty, Monroeville, PA
    2. Clinical Pharmacology Laboratory, Auburn University, College of Veterinary Medicine, Auburn, AL
    3. Matthew J. Ryan Veterinary Hospital of the University of Pennsylvania, Philadelphia, PA
    4. Bay Area Veterinary Specialists, San Leandro, CA
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  • FRANCES SHOFER PhD,

    1. Allegheny Veterinary Emergency Trauma and Specialty, Monroeville, PA
    2. Clinical Pharmacology Laboratory, Auburn University, College of Veterinary Medicine, Auburn, AL
    3. Matthew J. Ryan Veterinary Hospital of the University of Pennsylvania, Philadelphia, PA
    4. Bay Area Veterinary Specialists, San Leandro, CA
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  • JEFFREY S. DAVIDSON,

    1. Allegheny Veterinary Emergency Trauma and Specialty, Monroeville, PA
    2. Clinical Pharmacology Laboratory, Auburn University, College of Veterinary Medicine, Auburn, AL
    3. Matthew J. Ryan Veterinary Hospital of the University of Pennsylvania, Philadelphia, PA
    4. Bay Area Veterinary Specialists, San Leandro, CA
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  • R. AVERY BENNETT DVM, MS, Diplomate ACVS

    1. Allegheny Veterinary Emergency Trauma and Specialty, Monroeville, PA
    2. Clinical Pharmacology Laboratory, Auburn University, College of Veterinary Medicine, Auburn, AL
    3. Matthew J. Ryan Veterinary Hospital of the University of Pennsylvania, Philadelphia, PA
    4. Bay Area Veterinary Specialists, San Leandro, CA
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  • Presented in part at the 32nd Annual Conference of the Veterinary Orthopedic Society, Snowmass, CO, March 6–15, 2005.
    Research conducted at, and funded in part by the Matthew J. Ryan Veterinary Hospital of the University of Pennsylvania, Philadelphia, PA.

Address reprint request to Dr. Heidi Phillips, VMD, Diplomate ACVS, Allegheny Veterinary Emergency Trauma and Specialty, 4224 Northern Pike, Monroeville, PA 15146. E-mail: sxn2005@comcast.net.

Abstract

Objective— To compare the in vitro elution characteristics of amikacin and cefazolin from polymethylmethacrylate (PMMA) alone and in combination.

Study Design— A prospective, controlled, experimental study.

Methods— Three aliquots of 6 g sterile PMMA were measured and to them added (1) 750 mg amikacin; (2) 1050 mg cefazolin; and (3) 750 mg amikacin and 1050 mg cefazolin. Ten beads of each antimicrobial/PMMA combination were placed in 5 mL phosphate-buffered saline (PBS) at pH 7.4 and room temperature with constant agitation. PBS was sampled at 15 time points between 1 hour and 30 days. Amikacin concentrations were determined by fluorescence polarization immunoassay and cefazolin concentrations by high-performance liquid chromatography.

Results— Amikacin and cefazolin eluted at concentrations greater than 8 and 4 times, respectively, above the minimum inhibitory concentration (MIC) for susceptible bacteria over 30 days. Co-elution of the antibiotics resulted in a greater rate and proportion of antibiotic eluted. Concentrations of amikacin and cefazolin in the co-eluted fluid were not maintained sufficiently above the MIC for selected bacteria over 30 days.

Conclusions— PMMA beads of only amikacin or cefazolin-eluted concentrations greater than the MIC for selected bacteria for 30 days. Co-elution of the antibiotics at the selected doses resulted in a significantly shorter duration of elution and may not be effective for treatment of wound infection.

Clinical Relevance— Co-elution of amikacin and cefazolin from PMMA at the selected doses cannot be recommended for sustained treatment of infection.

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