[Resorbable antibiotic delivery systems in local treatment of chronic osteitis--polyglycolic acid/poly-L-lactide as drug carrier. Experimental studies in vitro].

Resorbable polyglycolic acid (PGA)- and poly-L-lactic acid (PLLA) cylinders were investigated in vitro to explore their properties as an antibiotic deposit (Ciprobay, Bayer Leverkusen) with prolonged release. PGA cylinders sized 3.2 x 5 mm, 4.5 x 5 mm and 4.5 x 7 mm respectively were shaped in monofil and polyfil technique. The Ciprofloxacin concentration varied from 0.5 mg to 5.0 mg of each cylinder. The cylinders were eluated in phosphate buffer, pH-value of 7.4, at 37 degrees C. The daily antibiotic release was measured by high performance liquid chromatography. Best combinations we could find demonstrated an initial delivery of Ciprofloxacin in vitro of 67 mg/l. The average daily release was about 16 mg/l during the first 36 days. After complete hydrolysis of the PGA carriers the recovery of Ciprofloxacin reached up to 6.5% and 11.6% respectively. For 40 bioactive cylinders (size phi 3.5 mm x 5 mm, containing 4 mg Ciprofloxacin) were eluated with phosphate buffer (pH 7.4 at 37 degrees C) respectively fresh human blood plasma and tested under various conditions. A gentamicin-polymethylmetacrylate (PMMA) chain (Septopal, E. Merck, Darmstadt) was exposed to equal test conditions for comparison. The quantities of released Ciprofloxacin and Gentamicin were analysed by a microbiological method (bioassay). Initially released rates of Ciprofloxacin were measured very high (up to 180 mg/l) but decreased rapidly within the first 5 days (4.2-22.5 mg/l). The release of Gentamicin produces an initial sharp decrease in concentration during the first 3 days (from 227.5 mg/l to 77.5 mg/l); this is then followed by an almost constant release over a long period of time (about 20 mg/l).(ABSTRACT TRUNCATED AT 250 WORDS)