For an adequate dose adjustment of highly protein-bound drugs like ertapenem, knowledge of actual albumin concentrations is necessary. A shortening of the dosage interval or continuous infusion of ertapenem should be considered to ensure optimal free concentrations in critically ill patients with severe hypoalbuminaemia and normal renal function.

The extent of induction of CYP3A varies among St. John's wort products and depends on hyperforin dose.

The pharmacokinetics of piperacillin-tazobactam were investigated in eight anuric intensive care patients treated by continuous venovenous hemodialysis (CVVHD). The elimination half-life of piperacillin was 4.3 ؎ 1.2 h, and that of tazobactam was 5.6 ؎ 1.3 h. The contribution of CVVHD to the overall elimination was relevant (>25%) for both drugs.Piperacillin-tazobactam is a ␤-lactam-␤-lactamase inhibitor combination with a broad spectrum of antibacterial activity against gram-positive as well as gram-negative pathogens. It is frequently used for the empirical treatment of infection in intensive care patients (2, 15). The aim of this investigation was to determine the pharmacokinetics of piperacillin-tazobactam in critically ill patients with acute anuric renal failure treated by continuous venovenous hemodialysis (CVVHD).Eight critically ill patients were included in the investigation (Table 1). Inclusion criteria were an age of Ͼ18 years, acute renal failure treated by CVVHD, anuria (Ͻ100 ml of urine/day), and treatment with piperacillin-tazobactam. Patients with severe liver failure or cholestasis were excluded. The protocol of the study was approved by the local ethical committee, and informed consent was obtained from a first-degree relative. CVVHD was performed with an AN69 hollow-fiber dialyzer (Multiflow 60; Hospal, Nuremberg, Germany) under the following conditions: a blood flow rate of 150 ml/min, a dialysate flow rate of 1.5 liters/h, and an ultrafiltrate flow rate of 80 to 200 ml/h. Doses of piperacillin-tazobactam (4.5 g of Tazobac; Wyeth-Lederle) and dosing schedules were chosen empirically by the attending physicians (Table 2). Piperacillin-tazobactam was administered intravenously over 15 min. Corresponding predialyzer blood samples and dialyzer-outlet dialysate samples were taken before drug administration, at 10 and 30 min after infusion, and at 1, 2, 4,6,8,12,20, 22, and 24 h after infusion. Sampling was performed in the first dosage interval after the dialyzer membrane was changed. Blood samples were centrifuged immediately after they were taken, and plasma and dialysate samples were frozen at Ϫ80°C until analysis. The concentrations of piperacillin and tazobactam were determined by reversed-phase high-performance liquid chromatography with UV detection, with modification of the methods reported previously (13, 16). Plasma specimens were deproteinated, and dialysate was used without pretreatment. The presence of piperacillin was determined from the water layer extracted with dichloromethane; tazobactam samples were derivatized with 1,2,3-triazole and injected without extraction. The chromatographic conditions for piperacillin were as follows: a guarded Nucleosil C 18 100-5/250 ϫ 4 column, an eluent of methanol-KH 2 PO 4 (1:1, vol/vol; 67 mM; pH 3), ambient temperature, a flow rate of 0.5 ml/min, a of 214 nm, and a retention time of ϳ20 min. The chromatographic conditions for tazobactam were as follows: a Superspher C 18 100-5/250 ϫ 4 column; an eluent of acetonitrile-Na 2 HPO 4 (1:3, vol/vol; ...

Objective Induction of CYP3A by St. John's wort (SJW) products with high hyperforin content is well described. Since CYP3A induction is mediated by hyperforin in a concentration-dependent manner, and SJW preparations differ significantly in hyperforin content, the aim of the study was to evaluate the effect of an SJW powder with low hyperforin content on CYP3A function. Methods Twenty healthy male volunteers received an SJW powder with low hyperforin content for 2 weeks. Midazolam plasma concentration time profiles were characterized after a single oral dose of 7.5 mg midazolam on the day before and on the 14th day of SJW medication. Results Midazolam AUC 0-∞ slightly decreased from 124.0 ± 62.5 ng/ml·h at baseline to 105.6 ± 53.2 ng/ml·h after SJW (P < 0.05), representing a mean 11.3% decrease (95% CI: −22.8 to 0.21). No significant change in midazolam C max , t 1/2 and t max was observed. For all pharmacokinetic parameters, the 90% CI for the geometric mean ratio of treatment over baseline were within the no-effect boundaries of 0.70-1.43. Conclusion Administration of an SJW product with low hyperforin content resulted in a mild induction of CYP3A not considered clinically relevant.

Plasma pharmacokinetics of linezolid in diabetics and adequate levels in inflamed areas of diabetic foot wound suggest that an oral dose of 600 mg bd of linezolid provides effective concentrations for treating methicillin-resistant Staphylococcus aureus (MRSA) in DFI.