Comparative pharmacokinetics of cefoxitin in postpartum normotensive and pregnancy-induced hypertensive patients

Pharmacokinetics of three-dose cefoxitin prophylaxis in caesarean section

A pharmacokinetic analysis of cefoxitin in women undergoing caesarean section under general anaesthesia, was performed. In order to prevent infections postoperatively three doses of cefoxitin--2, 1 and 1 g, respectively--were given as a 3-min intravenous infusion at 6-h intervals. In vitro growth of most pathogens is inhibited at a cefoxitin concentration of 16 micrograms/ml. In the sera of the patients, this antibiotic level was maintained for a period of 90-100 min after the first administration (2 g) and 45-50 min after the second and the third administration of cefoxitin (1 g). The period of subinhibitory antibiotic concentrations lasted 270 and 315 min, respectively. How can one reach prolonged antibiotic coverage? In order to minimize antibiotic pressure on hospital flora it is advisable not to increase the total amount of antibiotic (4 g) administered. By starting a 310 mg/h infusion after the initial 2 g bolus injection, the serum concentration of cefoxitin can be maintained at a minimum level of 16 micrograms/ml during a period of 6.5 h. The improvement of antibiotic administration suggested requires further clinical testing.

Pharmacokinetics of cefoperazone in the parturient

Limited pharmacokinetic data for cefoperazone are available from the parturient. Because cefoperazone has a dual excretory pattern, primarily via the biliary system and secondarily via the kidney, pregnancy-induced physiologic alterations can influence its deposition and clearance. Twelve term parturients receiving cefoperazone prophylaxis after cesarean section were selected for study. After 2 g of cefoperazone was administered for 1 h intravenously, serial blood samples were assayed by high-pressure liquid chromatography. Plasma protein binding of cefoperazone was studied in vitro. The mean peak cefoperazone concentration +/- standard deviation was 169.9 +/- 60.4 micrograms/ml. The mean half-life was 152 min. Total serum clearance was 80.8 +/- 30.8 ml/min. The steady-state volume of distribution was 14.2 +/- 6.0 liters. All subjects had detectable trough levels at the end of the dosage interval, with a mean value of 6.5 +/- 5.2 micrograms/ml. Protein binding of cefoperazone for parturients was 74.3 +/- 10.9%, compared with 87.7 +/- 3.2% in nonpregnant controls (P less than 0.05). These data suggest that cefoperazone deposition can be greatly influenced by pregnancy. However, unlike several other new antimicrobial agents whose excretions are mainly renal, the cefoperazone half-life and thus trough concentration for the parturient more closely resemble that for the nonpregnant subject.