[Release of 14c-chloramphenicol in the rabbit femur implanted with polymethylmetacrylate (author's transl)]

In vitro studies and animal experiments were started for the purpose of following the migration of chloramphenicol marked with 14C from polymerised polymethylmetacrylate cylinders. Test-cylinders were submerged in a physiological saline solution and the 14C concentration followed over a period of 34 days. Two series were started with the cylinders being submerged at intervals of 5 and 40 min after the start of polymerisation. These in vitro studies showed that initially the migration of active substances marked with 14C from the plastic cylinders was extremely high but remained then constant over the whole test period. Over a period of at least 20 days a higher 14C migration was evident in those cylinders submerged in the elution 5 min after the start of polymerisation. In our in vivo studies we implanted test-cylinders into the femur of rabbits. The migration of active substances marked with 14C resulted in 14C-concentrations being present in the surrounding tissues. During the phase of exudation, depending on the operative process, the concentration increased and reached values that remained constant during the phase of recanalisation of the surrounding tissues over a period of up to 6 weeks. Thereafter the concentration of active substances fell. The max. concentration rates of active substances within the boundary layer were between 15 and 20 mug/g humidity weight. After 8 weeks we found concentration rates of approx. 1 mug/g humidity weight. On examining the 14C distribution within the implanted plastic cylinders we observed that in the course of time the boundary layer increased in thickness and a concentration gradient towards the centre had developed. The spread of diffusion gradually seized the deeper layers so that a long-lasting presence of active substances may be expected.