Ceftriaxone pharmacokinetics during iatrogenic hydroxyethyl starch-induced hypoalbuminemia: a model to explore the effects of decreased protein binding capacity on highly bound drugs.

BACKGROUND Although various drugs used by anesthesiologists highly bind to plasma proteins, the impact of iatrogenically induced hypoproteinemia on their pharmacologic effects has never been investigated. The authors determined the pharmacokinetics of ceftriaxone, a cephalosporin that binds strongly to albumin in postsurgical patients with hydroxyethyl starch-induced hypoalbuminemia. METHODS Eleven hypoalbuminemic (serum albumin < 25 g/l) patients and age (+/- 5 yr)-, sex-, and body surface area (+/- 10%)-matched healthy volunteers received a 2-g ceftriaxone dose infused over a 15-min period. Fourteen venous blood samples were collected during the 24-h study period. Free ceftriaxone concentrations were determined by ultrafiltration. Antibiotic concentrations in plasma and ultrafiltrate were measured by ion-paired reversed-phase chromatography. The pharmacokinetic parameters derived from total and free antibiotic concentrations were determined using a noncompartmental method. Data are expressed as median and range. RESULTS The pharmacokinetic parameters derived from total ceftriaxone concentrations were similar for the two groups, except for the median corrected volume of distribution at steady state, which was increased (P = 0.05) to 0.18 l/kg (range, 0. 11-0.29 l/kg) in patients, compared with 0.15 l/kg (range, 0.13-0.22 l/kg) in volunteers. The area under the free ceftriaxone concentration-time curve was twice as high in patients as in volunteers (median 192, range 114-301 vs. median 122, range 84-169 h. mg-1. l-1;P = 0.03). Moreover, the free ceftriaxone concentration remained more than 4 mg/l during more time in patients (median, 16. 7; range, 12.6-21.4 vs. median, 11.1; range, 6.0-19.0 h; P = 0.03). CONCLUSIONS Compared with healthy volunteers, patients with iatrogenic hypoalbuminemia have higher free ceftriaxone concentrations during the 24 h after antibiotic administration. This modification increases drug distribution into extravascular space and may enhance effectiveness.