[Experimental study of acrylic resin coated gentamicin tablets for local antibiotic therapy]

Gentamicin tablets were prepared and evaluated for local antibiotic therapy. Two types of tablet were used. One, a slow release tablet, was coated with acrylic resin (Eudragit R.S.) and another was non-coated. The release of gentamicin from the coated tablets can be controlled by changing the thickness of the film coating. The thickness of the film coating was adjusted to release gentamicin within three weeks when placed in Ringer's solution. Coated tablets were inserted into the bone marrow of rabbits. Thereafter, daily excretion of gentamicin was measured in the urine for three weeks. Constant excretion of gentamicin was seen for ten to fourteen days, which suggests the release of gentamicin from the bone marrow. Plasma concentrations were very low, thus precluding side effects. Non-coated tablets were inserted to the bone marrow by the same method as above. Plasma concentrations of gentamicin peaked in one hour and then rapidly decreased. This pattern is similar to that seen with intramuscular administration. As acrylic resin was non-absorbable material in vivo, the tissue reactions around coated tablets were examined. Histological findings at three weeks, six weeks and six months after insertion, respectively, did not show any severe tissue reactions. The possible use of local therapy by coated antibiotic tablets for bone infections is discussed.