[Penetration into bone and joint tissues of rabbits and in vitro antibacterial activity of tosufloxacin].

The penetration of tosufloxacin (TFLX) into the bone and joint tissues of rabbits and its in vitro antibacterial activity were compared with those of lomefloxacin (LFLX) which is a efficacious drug for orthopedic infections. Serum levels of TFLX at 1, 2, 4 and 6 hours after oral administration (100 mg/kg) were 0.41, 0.65, 0.62 and 0.42 micrograms/ml, respectively. Except in synovial fluid and femur, TFLX concentrations in bone and joint tissues were higher than those in serum (0.69 approximately 1.92 micrograms/g in bone marrow of sternum, 0.55 approximately 1.53 micrograms/g in bone marrow of femur). TFLX concentrations in synovial fluid at 4 and 6 hours after the administration were equal to those in serum, which were lower than those of LFLX, but the ratio of tissue level/serum level of TFLX was similar to that of LFLX. TFLX was 8- to 64-fold more active than LFLX against Staphylococcus aureus (including methicillin-resistant S. aureus), Streptococcus pyogenes, Haemophilus influenzae, which are major pathogens of purulent osteomyelitis and arthritis. TFLX inhibited the growth of these bacteria at less than 0.39 micrograms/ml. These results indicate that TFLX is a useful drug for orthopedic infection.