Aims To describe the pharmacokinetics (PK) of cefotaxime as pre‐emptive treatment in critically ill adult patients, including covariates and to determine the probability of target attainment (PTA) of different dosage regimens for Enterobacterales and Staphylococcus aureus. Methods Five samples were drawn during 1 dosage interval in critically ill patients treated with cefotaxime 1 g q6h or q4h. PK parameters were estimated using NONMEM (v7.4.2). The percentage of patients reaching 100% fT>MICECOFF was used to compare different dosage regimens for Enterobacterales and S. aureus. Results This study included 92 patients (437 samples). The best structural model was a 2‐compartment model with a combined error, interindividual variability on clearance, central volume and intercompartmental clearance. Correlations between interindividual variability were included. Clearance increased with higher estimated glomerular filtration rate (eGFR; creatinine clearance) and albumin concentration. For Enterobacterales, 1 g q8h reached 95% PTA and continuous infusion (CI) of 4 g 24 h−1 100% PTA at the highest eGFR and albumin concentration. For S. aureus the predefined target of 95% PTA was not reached with higher eGFR and/or albumin concentrations. CI of 6 g 24 h−1 for S. aureus resulted in a minimum of 99% PTA. Conclusion Cefotaxime PK in critically ill patients was best described by a 2‐compartment model with eGFR and albumin concentration as covariates influencing clearance. For Enterobacterales 1 g q8h or CI of 4 g 24 h−1 was adequate for all combinations of eGFR and albumin concentration. For S. aureus CI of 6 g 24 h−1 would be preferred if eGFR and albumin concentration exceed 80 mL min−1 and 40 g L−1 respectively.
For decades, flucloxacillin has been used to treat methicillin-susceptible Staphylococcus aureus (MSSA). Little is still known about its pharmacodynamics (PD). The present study aimed to determine the pharmacokinetic (PK)/PD index and the PD-index value minimally required for efficacy. MICs of 305 MSSA isolates were measured to determine the wild-type distribution. The PD of 8 S. aureus, 1 S. pyogenes, and 1 S. agalactiae isolates were evaluated in a neutropenic murine thigh infection model. Two S. aureus isolates were used in a dose-fractionation study and a dose–response analysis was performed additionally in the in vivo model. Data were analyzed with a population PK and sigmoid maximum effect model. The end of the wild-type distribution was 1 mg/L. The percentage of time the unbound concentration was above MIC (%fT > MIC) was best correlated with efficacy. For S. aureus, median %fT > 0.25 × MIC required for 1-log reduction was 15%. The value for S. pyogenes was 10%fT > MIC and for S. agalactiae 22%fT > 0.25xMIC for a 1-log reduction. The effect of flucloxacillin reached a 2-log reduction of S. aureus at 20%fT > 0.25xMIC and also for S. pyogenes and S. agalactiae, a reduction was reached. These data may serve to optimize dosing regimens currently used in humans.
In this article, 2 cases of intentional dothiepin intoxication are presented. Both patients survived after receiving appropriate supportive care. The dothiepin and metabolite levels were measured at different times after ingestion. The initial levels of dothiepin were 1900 microg/L in case 1 and 5500 microg/L in case 2. In case 1, a toxicokinetic model was fitted, suggesting a higher peak level, corresponding with the QRS duration and clinical symptoms. In case 2, a combined dothiepin-ethanol intoxication was seen, complicating the interpretation of clinical parameters, such as the QRS duration. In conclusion, the severity of dothiepin intoxication is poorly predicted by plasma levels alone, as time of ingestion can be critical for interpretation. However, especially in combined intoxications, interpretation of the QRS duration may also fail. Therefore, it is important to evaluate the whole range of clinical parameters, QRS duration, clinical symptoms, dothiepin concentration(s), and other possible intoxications.
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