Phosphomycin levels in serum and interstitial tissue fluid in a multiple dosage regimen in rabbits.

The evolution of phosphomycin (Fosfocina), levels in serum and experimentally induced interstitial tissue fluid and the access of the drug to different organs were studied in rabbits after the administration of a single dose of 60 mg/kg and during a multiple dosage regimen of 60 mg/kg/6 h over three days. Following the administration of a single dose a Cmax value of phosphomycin in interstitial tissue fluid of 80.4 micrograms/ml was reached at 1.2 h. The elimination half-life of the drug from the systemic circulation after a single dose had a value of 1.6 h, and was not significantly different from the value found for the same parameter in the multiple dosage regimen. The disappearance half-life of phosphomycin from interstitial tissue fluid, with a value of 1.9 h for the single dose schedule, was not significantly different from the value of the disappearance half-life of the drug from interstitial tissue fluid in the multiple dosage regimen. Finally, the results of the present study confirm the linearity of phosphomycin kinetics, at least in the conditions studied, and show that the drug is not accumulated in the organs considered.