Identifying alternative antibiotics that elute from calcium sulfate beads for treatment of orthopedic infections

There has been increasing interest in the use of a synthetic absorbable calcium sulfate (CaSO₄) for local antibiotic delivery in orthopaedic infections. The purpose of this study was to quantify elution kinetics of six antibiotics (amikacin, meropenem, fosfomycin, minocycline, cefazolin, and dalbavancin) from a clinically relevant CaSO₄ bead model and compare elution and antimicrobial activity to the current clinical gold standards: vancomycin and tobramycin. Antibiotic-loaded synthetic CaSO₄ beads were immersed in phosphate buffered saline and incubated at 37°C. Eluent was harvested at eight time points over 28 days. Antibiotic concentrations were measured by high performance liquid chromatography to quantify elution rates. CaSO₄ beads demonstrated burst release kinetics. Dalbavancin, cefazolin, and minocycline all demonstrated similar elution profiles to vancomycin. Amikacin and meropenem demonstrated favorable elution profiles and durations of above-minimum inhibitory concentration when compared to tobramycin.