Pharmacokinetic-pharmacodynamic comparison of ceftriaxone regimens in acute cholangitis

The most important factors determining the prognosis of patients with acute cholangitis (AC) are prompt biliary drainage and appropriate choice of antibiotics. This study was performed to evaluate whether dividing the number of doses based on the PK-PD theory contributes to better clinical outcome in the management of acute cholangitis. We measured ceftriaxone levels in blood and bile in 21 cases diagnosed with moderate-to-severe AC. Eleven cases were administered 2 g of ceftriaxone once-daily (group A) and 10 cases were given 1 g of ceftriaxone twice-daily (group B). The theoretical effect of ceftriaxone was evaluated by pharmacokinetic-pharmacodynamic (PK-PD) parameters. Clinical efficacy was evaluated by body temperature, white blood cell count and serum levels of C-reactive protein. Minimum level of ceftriaxone in serum (in mg/L) in groups A and B at 24 h after the first dose was 9.1 and 9.2, whereas that in bile was 2.9 and 2.5, respectively. The minimum inhibitory concentration (MIC) of ceftriaxone for all isolated bacteria was below the minimum serum and biliary concentration of ceftriaxone 24 h after the first administration (except for Enterococcus species). The MIC for isolated bacterial strains was <16 mg/L, which is the PK-PD breakpoint for ceftriaxone at 2 g/day. Both regimens showed clinical efficacy and did not contradict the effect predicted based on PK-PD.