Comparison of the pharmacodynamics of biapenem in bronchial epithelial lining fluid in healthy volunteers given half-hour and three-hour intravenous infusions.

The time above the MIC (T>MIC) is the pharmacokinetic/pharmacodynamic (PK/PD) parameter that correlates with the therapeutic efficacy of beta-lactam antibiotics. A prolonged infusion can provide plasma drug concentrations that remain above the MIC for a long period. The objective of this study was to compare the PK/PD parameters in bronchial epithelial lining fluid (ELF) of biapenem given as 0.5-h and 3-h infusions by using bronchoscopic microsampling (BMS). Six healthy adult volunteers received 0.5-h and 3-h infusions of 0.3 g of biapenem with a washout interval. BMS was performed repeatedly from 0.5 to 24 h after biapenem administration in order to determine the pharmacokinetics in bronchial ELF. The subjects received intravenous biapenem with the same regimens again and then underwent bronchoalveolar lavage (BAL) at the end of infusion in order to determine the concentration of the drug in alveolar ELF. The percentages (means +/- standard deviations) of T>MIC in bronchial ELF at MICs from 0.25 to 4 microg/ml ranged from zero to 34.6% +/- 5.2% after the 0.5-h infusion and from 5.1% +/- 5.6% to 52.2% +/- 17.0% after the 3-h infusion. The percentage of T>MIC in bronchial ELF after the 3-h infusion tended to be higher than that after the 0.5-h infusion. The concentrations of the drug in alveolar ELF after 0.5-h and 3-h infusions were 3.5 +/- 1.2 microg/ml and 1.3 +/- 0.3 microg/ml, respectively. The present results support the use of prolonged infusions of beta-lactam antibiotics and may provide critical information for successful treatment of lower respiratory tract infections based on PK/PD parameters in bronchial ELF.