CONTROLLED-RELEASE OF ANTIBIOTICS FROM BIOMEDICAL POLYURETHANES - MORPHOLOGICAL AND STRUCTURAL FEATURES

Polymer-associated infections are of increasing importance. Antistaphy lococcal antimicrobial substances (ciprofloxacin, gentamycin, fosfomyc in, flucloxacillin) were incorporated into polyurethanes by the solven t casting technique. Drug release rates, bacterial colonization and mo rphological features were evaluated to predict and understand the anti microbial activity of these delivery systems. Drug release characteris tics were investigated by standard bioassay and high-performance liqui d chromatography (HPLC), and the physico-chemical mechanisms of the de livery were discussed. Ciprofloxacin hydrochloride showed a fast initi al release rate, whereas gentamicin-base was characterized by a more c ontinuous release type of behaviour. Bacterial colonization to the ant ibiotic-loaded polyurethanes was inhibited effectively by preparations showing a slower but more sustained antimicrobial delivery. Polyureth ane-antibiotic combinations were most homogeneous for gentamicin-base and flucloxacillin as shown by scanning electron microscopy (SEM). In polymers loaded with fosfomycin and ciprofloxacin a granular structure of the crystallized drug embedded in the polyurethane matrix could be demonstrated. Physico-chemical similarity of the polymeric material a nd the antibiotics is important for the homogeneity of polymer-antibio tic combinations. High homogeneity is required for a sustained and pro longed release over time and effective inhibition of bacterial coloniz ation. (C) 1997 Elsevier Science Limited.