Sample collection
Cefoperazone/sulbactam (Sulperazon, Pfizer, New York, USA) with cefoperazone 2.0 g/sulbactam 1.0 g in a 3-g ampoule was given to patients. A dose of 3.0 g CFP/SUL for adults was added to 100 mL of 0.9% normal saline solution and was administered by intravenous injection using an infusion pump at the usual rate for 60 min every 8 h. Each TPE session began 10 min after the end of the CFP/SUL infusion. 3 mL blood anticoagulated with EDTA were collected from median cubital vein. To evaluate the effect of TPE on the pharmacokinetics of CFP and SUL, whole blood samples were collected during two sessions.
Session I, the third dose of CFP/SUL was administered on the first day with TPE. Serial venous blood samples were collected at time 0 (trough concentration), time 1 (peak level, 10 min before TPE), and time 2, 3, 4, 6, 8 h after the start of drug infusion. An aliquot was also taken from the effluent port of plasma eliminated during TPE.
Session II, before the following day’s TPE, a series of venous blood samples were collected respectively at the same time points at the sixth CFP/SUL administration without TPE.
Whole blood samples were centrifuged at 4°C at 3000 rpm for 10 min, and then the plasma was separated. All plasma samples were stored at -80°C until analysis.