[Plaster of Paris: a carrier for antibiotics in the treatment of bone infections].

Local antibiotherapy by diffusion from plaster of Paris is a promising method in orthopedic surgery. Nevertheless, the characteristics of this matrix have not yet been extensively studied with respect to regulation of drug-carrier capacity. From the careful comparative investigation of five commercialized plasters of Paris, it appears that the material must be constituted of fine homogeneous crystals devoid of any additive in order to obtain reproducible implants which are sufficiently hard. This condition determines their use as a biodegradable filler of bone cavities. Because of the antimicrobial spectrum, diffusion velocity and synergistic effect of sodium fusidate, amoxicillin trihydrate and sodium amoxicillin, this association of antibiotics with the plaster of Paris appears to be a useful sterilizing delivery system. The plaster of Paris allows a significant release of sodium amoxicillin during the first 3 days. This is followed by an important sustained liberation of sodium fusidate and amoxicillin trihydrate for one week. Finally, the local release of sodium fusidate for at least 2 weeks at concentrations higher than the minimum inhibition concentrations (MIC) of the most frequently infecting pathogens in osteomyelitis, will allow the sterilization of bone cavities.