[Study of concentrations of clindamycin phosphate in bone marrow blood and tissue]

Clindamycin phosphate (CLDM) was administered to 33 surgical cases in orthopedics to treat or prevent infection (600 mg in 15 cases and 1,200 mg in 18 cases by intravenous drip infusion over 60 minutes) and the concentrations of CLDM in the bone marrow blood and tissue of the operative field as well as in venous blood were determined with the cup plate method of bioassay by collecting specimens immediately after completion of infusion or 30 or 60 minutes later. The concentration of CLDM in bone marrow blood averaged 104.3 approximately 105.5% of the corresponding concentration in venous blood in the cases receiving 600 mg and 101.3% in those receiving 1,200 mg. The concentration of CLDM in bone marrow tissue averaged 154.0 approximately 163.7% of the corresponding concentration in venous blood in the group receiving 600 mg but 78.8 approximately 86.2% in the group receiving 1,200 mg. This difference between the 2 groups was considered to reflect largely the difference in specimens collected. Thus, the concentration of CLDM in bone marrow tissue was interpreted as the amount of drug penetrating and remaining in bone marrow tissue and its adjacent area. The MIC75 of CLDM for clinical isolates were 0.20 micrograms/ml for S. aureus, 0.78 micrograms/ml for B. fragilis and 0.20 micrograms/ml for Peptostreptococcus spp. The concentrations of CLDM attained in bone marrow blood and tissue and its adjacent area after administration of 600 mg or 1,200 mg were thus sufficient to eliminate these organisms. The above results indicate that CLDM is a useful antibiotic for treatment and prevention of infection in orthopedics.