Antibiotic polymer prostheses.

Antibiotic polymer prostheses 

Polymer plastics are already being used as implanted, controlled-release drug-delivery systems (SN: 6/4/88, p.360). Now researchers at the University of Cologne in West Germany are investigating a variation on this theme -- the design of antibiotic-impregnated polymers for artificial heart valves and cardiac-pacemaker electrodes.

Skin bacteria often contaminate the surface of polymer prosthetic devices, causing serious infections, explains Bernd Jansen. Once such an infection occurs, he says, removal of the plastic device is usually necessary because antibiotic treatment of the patient at this stage is seldom successful. But he and his co-workers incorporated different antibiotics into polyetherurethane plastics at concentrations as high as 5 percent by weight. In test environments simulating body implantation, thin films of these plastics released either of the antibiotics clindamycin or flucloxacillin at constant, high rates for at least five days. And the Cologne scientists were able to tailor the rate of drug release by pretreating the plastic with gamma irradiation. Though the released antibiotics did not completely inhibit bacterial colonization of the plastic, Jansen reports data from in vitro tests showing they could reduce viable bacterial numbers to as little as one ten-thousandth of the original population.