The pharmacokinetics and tissue penetration of intravenously administered CGP 31608

The pharmacokinetics of CGP 31608, a new injectable penem antibiotic, were studied following a 1 g intravenous infusion. Concentrations were determined in serum, urine and cantharidin-induced inflammatory fluid by a microbiological assay. Peak serum concentrations were achieved at, or before the end of, the 1 h infusion, with a mean of 24.9 mg/l occurring at 0.8 h. The mean serum elimination half-life was 0.5 h, with no detectable drug in serum after 3 h. Inflammatory fluid was penetrated rapidly with a mean peak level of 10.5 mg/l occurring at 1.3 h (i.e. 20 min after the end of the infusion). Urinary elimination of CGP 31608 accounted for 52.1% of the administered dose within an hour of finishing the infusion, and 57.1% by 12 h. This study suggests that therapeutic serum levels (greater than 8 mg/l) are present for about 1.5 h after starting a 1 h infusion, and in inflammatory fluid for about 2.5 h. Unless a dose in excess of 1 g is used, CGP 31608 will probably have to be given four or more times a day.