Carrier systems for the local delivery of antibiotics in bone infections

Carriers used for the local delivery of antibacterial agents may be classif ied as nonbiodegradable or biodegradable. A major representative of the for mer category are the polymethylmethacrylate (PMMA) beads often impregnated with gentamicin which have been commercially available for the last 2 decad es. Examples of the latter category include the collagen-gentamicin sponge, apatite-wollastonite glass ceramic blocks, hydroxyapatite blocks, polylact ide/polyglycolide implants and the polylactate polymers. All of the above s ystems release antibiotics at concentrations exceeding those of the minimum inhibitory concentrations (MICs) for the most common pathogens of chronic osteomyelitis without releasing any antibiotic in the systemic circulation and without producing adverse effects. The major disadvantage of the PMMA b eads is the need for their surgical removal at the completion of antibiotic release, which usually takes place 4 weeks after their implantation. The b iodegradable carriers do not require surgical removal, and of those listed, the collagen-gentamicin sponge has been applied successfully over the last decade for bone infections. Among the other biodegradable systems which ar e still in experimental stages, polylactate polymers carrying quinolones se em very promising, since they are characterised by prolonged duration of re lease at concentrations 100 to 1000 times the MICs of the causative bacteri a implicated in bone infections; preliminary results have shown these carri ers to be very effective in the management of experimental osteomyelitis ca used by methicillin-resistant Staphylococcus aureus. Further development of such biodegradable systems will provide a novel approach in the future for the eradication of chronic osteomyelitis.