First international quality control programme for laboratories measuring antimicrobial drugs to support dose individualization in critically ill patients.

OBJECTIVES: International quality control (proficiency testing) programmes are instituted to safeguard the analytical performance of laboratories and to aid these laboratories in identifying sources of error in their analytical methods. We describe the first international quality control programme for antimicrobial agents that are frequently used in critically ill patients. METHODS: Spiked plasma samples with ceftazidime, ciprofloxacin, flucloxacillin, piperacillin, sulfamethoxazole, N-acetyl sulfamethoxazole and trimethoprim were shipped to 22 laboratories from eight different countries. Acceptable accuracy by the performing laboratory was defined if measurements were within 80%-120% limits of the true weighed-in concentrations. RESULTS: A total of 81% of the measurements (ranging between 56% and 100%, dependent on drug) were within the 80%-120% limits of the true weighed-in concentrations. CONCLUSIONS: We found a relatively good performance of the participating laboratories in measuring eight different antimicrobial drugs. Nevertheless, some of the antimicrobial drugs were not measured properly as up to 44% of the measurements was inaccurate depending on the drug. Our results emphasize the need for and utility of an ongoing quality control programme.

Exposure to total and protein-unbound rifampin is not affected by malnutrition in Indonesian tuberculosis patients.

Nutritional status may have a profound impact on the pharmacokinetics of drugs, yet only few data are available for tuberculosis (TB) drugs. As malnutrition occurs frequently among TB patients, we assessed the effect of malnutrition on the steady-state pharmacokinetics of total and protein-unbound rifampin during the intensive phase of TB treatment. In a descriptive pharmacokinetic study in Bandung, Indonesia, patients received a fixed standard rifampin dose of 450 mg once daily during the intensive phase of TB treatment. A full pharmacokinetic curve for rifampin was recorded, and total and unbound concentrations of rifampin were analyzed in all samples. Rifampin pharmacokinetic parameters were compared between severely malnourished (BMI of <16.0 kg/m(2)), malnourished (BMI of <18.5 kg/m(2)), and well-nourished (BMI of ≥18.5 kg/m(2)) individuals. No difference in total and protein-unbound pharmacokinetic parameters between severely malnourished (n = 7), malnourished (n = 11), and well-nourished (n = 25) patients could be demonstrated. In addition, no significant correlation between BMI and exposure (area under the concentration-time curve from 0 to 24 h [AUC0-24] and maximum concentration of drug in serum [Cmax]) was found. Females had significantly higher total AUC0-24 (geometric mean, 59.2 versus 48.2 h · mg/liter; P = 0.02) and higher unbound AUC0-24 (geometric mean, 6.2 versus 4.8 h · mg/liter; P = 0.02) than males. Overall, a marked 2-fold interindividual variation in the free fraction was observed (7.6 to 15.0%; n = 36). Nutritional status and BMI do not appear to have a major effect on total and protein-unbound pharmacokinetic parameters of rifampin in Indonesian subjects. The large interindividual variability in the free fraction of rifampin suggests that protein-unbound rather than total rifampin concentrations should preferably be used to study exposure-response relationships.

Effect of efavirenz treatment on the pharmacokinetics of nelfinavir boosted by ritonavir in healthy volunteers.

AIMS: A once-daily (q.d.) nucleoside-sparing regimen can prevent mitochondrial toxicity, overcome viral resistance and improve compliance. In the present study the effect of efavirenz on the pharmacokinetics and tolerability of once-daily nelfinavir/ritonavir was evaluated in healthy subjects. METHODS: This was a multiple-dose, open-label, single-group, two-period study in 24 healthy subjects. Each received from days 1-10 (period 1): 1875 mg nelfinavir plus 200 mg ritonavir q.d. with a 300-kcal snack. During days 11-20 (period 2) efavirenz 600 mg q.d. was added to the regimen. Blood samples were collected up to 24 h after dosing on days 10 (period 1) and 20 (period 2). High-performance liquid chromatography methods were used for the determination of the concentrations of all compounds. The main pharmacokinetic parameters were calculated using noncompartmental methods. RESULTS: All subjects completed the study. After the first period mean nelfinavir AUC(0-24 h), C(max) and C(24) were 49.6 mg h(-1) l(-1), 5.0 mg l(-1) and 0.37 mg l(-1), and the sum of nelfinavir plus its active metabolite M8 C(24) was 0.83 mg l(-1). The relative bioavailability, expressed as a geometric mean ratio (90% confidence interval) for nelfinavir AUC(0-24 h), C(max) and C(24) of period 2 compared with period 1 was: 1.30 (1.21, 1.40), 1.29 (1.19, 1.40) and 1.48 (1.32, 1.66). The sum of nelfinavir and M8 C(24) in period 2 was 0.99 mg l(-1), an increase of 19%. No serious adverse events occurred. CONCLUSIONS: The studied regimens were well tolerated. Nelfinavir/ritonavir given together with efavirenz resulted in a 48% higher mean C(24) concentration for nelfinavir, and the sum of nelfinavir and M8 C(24) concentrations was 0.99 mg l(-1). Efavirenz exposure in this study was similar to that reported previously, and therefore can be used effectively in combination with ritonavir and nelfinavir.

Pharmaceutical development of a parenteral formulation of the novel anti-tumor agent carzelesin (U-80,244).

The aim of this study was to design a parenteral dosage form for the investigational cytotoxic drug carzelesin. A stable formulation in PET (Polyethylene glycol 400/absolute ethanol/Tween 80, 6:3:1, v/v/v) was developed. The prototype, containing 0.50 mg carzelesin in 2.0 ml PET formulation, was found to be the optimal formulation in terms of solubility, stability and dosage requirements in phase I clinical trials. Quality control of the formulation showed that the pharmaceutical preparation of carzelesin in PET is not negatively influenced by the manufacturing process. Shelf life studies demonstrated that the formulation is stable for at least 1 year, when stored at -30 degrees C in the dark. In addition, the stability of carzelesin in the PET formulation is discussed as a function of temperature, additives and after dilution in infusion fluids.