Elution characteristics of tobramycin from polycaprolactone in a rabbit model

This study investigated the elution characteristics of tobramycin from poly caprolactone, a bioabsorbable polymer, in a rabbit model. Sixty rabbits wer e divided into two groups. Group I had polycaprolactone rods impregnated wi th 6% tobramycin surgically implanted into the proximal femoral intramedull ary canal. Group 2 received polymethylmethacrylate rods of like size, shape , and antibiotic concentration. Serum and urine samples were obtained, and tobramycin levels were determined via fluorescent immunosorbent assay. Rabb its were sacrificed as long as 56 days after surgery. Local bone tobramycin concentration was determined using the agar diffusion method. Polycaprolac tone delivered a significantly higher peak bone concentration of tobramycin (22.4 mug/mL) than did polymethylmethacrylate (13.59 mug/mL). Polycaprolac tone also had a more gradual decrease in local tobramycin concentration tha n did polymethylmethacrylate. Neither polycaprolactone nor polymethylmethac rylate yielded consistently detectable (> 0.1 mug/mL) serum tobramycin leve ls. Urine concentrations mirrored those seen in bone, with polycaprolactone achieving significantly higher tobramycin concentrations than did polymeth ylmethacrylate. Polycaprolactone had superior elution characteristics compa red with polymethylmethacrylate in this lapine model, suggesting that polyc aprolactone might be a promising local antibiotic delivery vehicle for the treatment of osteomyelitis.