Comparative study of antimicrobial release kinetics from polymethylmethacrylate.

Polymethylmethacrylate loaded with antimicrobial agents (most commonly vancomycin and/or aminoglycosides) is used for treatment and prevention of orthopaedic infections. Emergence of organisms resistant to vancomycin or aminoglycosides or both has been reported. Therefore, we studied in vitro release from polymethylmethacrylate beads of antimicrobials with suitable spectra for orthopaedic infections, including cefazolin, ciprofloxacin, gatifloxacin, levofloxacin, linezolid, and rifampin (2.5%, 7.5%, and 15%). Beads were placed in a continuous flow chamber, and antimicrobial concentrations in chamber outflow were determined by bioassay at timed intervals thereafter. Release profiles were bimodal with initial rapid release of high concentrations followed by sustained, slow release. Antimicrobial agents studied showed varied release profiles, indicating that elution from polymethylmethacrylate is unique to individual antimicrobial agents. Increasing antimicrobial concentration in polymethylmethacrylate increased peak concentrations and area under the curve. Cefazolin, ciprofloxacin, gatifloxacin, levofloxacin, linezolid, and rifampin may be suitable for incorporation into polymethylmethacrylate for management of orthopaedic infections.