Population Pharmacokinetics of Colistin Sulfate in Critically Ill Patients: Exposure and Clinical Efficacy.

Background: Presently, colistin is commercially available in two different forms, namely, colistin sulfate and its sulphomethylated derivative, colistimethate sodium (CMS). However, in the currently reported studies, most of the clinical studies on colistin for parenteral use are referred to as CMS. Data on the pharmacokinetics (PK), clinical efficacy, and side effects of colistin sulfate in clinical use have not been reported. Methods: This retrospective study was performed on carbapenem-resistant organism (CRO)-infected patients treated with colistin sulfate for more than 72 h. The population pharmacokinetic model was developed using the NONMEM program. The clinical outcomes including clinical treatment efficacy, microbiological eradication, and nephrotoxicity were assessed. Monte Carlo simulation was utilized to calculate the probability of target attainment (PTA) in patients with normal or decreased renal function. Results: A total of 42 patients were enrolled, of which 25 (59.52%) patients were considered clinical treatment success and 29 (69.06%) patients had successful bacteria elimination at the end of treatment. Remarkably, no patient developed colistin sulfate-related nephrotoxicity. A total of 112 colistin concentrations with a range of 0.28-6.20 mg/L were included for PK modeling. The PK characteristic of colistin was well illustrated by a one-compartment model with linear elimination, and creatinine clearance (CrCL) was identified as a covariate on the clearance of colistin sulfate that significantly explained inter-individual variability. Monte Carlo simulations showed that the recommended dose regimen of colistin sulfate, according to the label sheet, of a daily dose of 1-1.5 million IU/day, given in 2-3 doses, could attain PTA > 90% for MICs ≤ 0.5 µg/mL, and that a daily dose of 1 million IU/day could pose a risk of subtherapeutic exposure for MIC ≥1 µg/ml in renal healthy patients. Conclusion: Renal function significantly affects the clearance of colistin sulfate. A dose of 750,000 U every 12 h was recommended for pathogens with MIC ≤1 µg/ml. The dosage recommended by the label inserts had a risk of subtherapeutic exposure for pathogens with MIC ≥2 µg/ml. Despite higher exposure to colistin in patients with acute renal insufficiency, dose reduction was not recommended.

Dosage Strategy of Linezolid According to the Trough Concentration Target and Renal Function in Chinese Critically Ill Patients.

Background: Linezolid is associated with myelosuppression, which may cause failure in optimally treating bacterial infections. The study aimed to define the pharmacokinetic/toxicodynamic (PK/TD) threshold for critically ill patients and to identify a dosing strategy for critically ill patients with renal insufficiency. Methods: The population pharmacokinetic (PK) model was developed using the NONMEM program. Logistic regression modeling was conducted to determine the toxicodynamic (TD) threshold of linezolid-induced myelosuppression. The dosing regimen was optimized based on the Monte Carlo simulation of the final model. Results: PK analysis included 127 linezolid concentrations from 83 critically ill patients at a range of 0.25-21.61 mg/L. Creatinine clearance (CrCL) was identified as the only covariate of linezolid clearance that significantly explained interindividual variability. Thirty-four (40.97%) of the 83 patients developed linezolid-associated myelosuppression. Logistic regression analysis showed that the trough concentration (Cmin) was a significant predictor of myelosuppression in critically patients, and the threshold for Cmin in predicting myelosuppression with 50% probability was 7.8 mg/L. The Kaplan-Meier plot revealed that the overall median time from the initiation of therapy to the development of myelosuppression was 12 days. Monte Carlo simulation indicated an empirical dose reduction to 600 mg every 24 h was optimal to balance the safety and efficacy in critically ill patients with CrCL of 30-60 ml/min, 450 mg every 24 h was the alternative for patients with CrCL <30 ml/min, and 600 mg every 12 h was recommended for patients with CrCL ≥60 ml/min. Conclusion: Renal function plays a significant role in linezolid PKs for critically ill patients. A dose of 600 mg every 24 h was recommended for patients with CrCL <60 ml/min to minimize linezolid-induced myelosuppression.

Trough polymyxin B plasma concentration is an independent risk factor for its nephrotoxicity.

AIMS: Data regarding clinical pharmacokinetic/toxicodynamic (PK/TD) of polymyxin B is short of direct quantitative data. This study aims to investigate the risk factors of polymyxin B associated acute kidney injury (AKI) and to assess the relationship between polymyxin B plasma levels and its nephrotoxicity. METHODS: A retrospective study was performed in adult patients treated with polymyxin B. Risk factors associated with AKI and plasma trough concentrations of polymyxin B were identified via medical record review. A multivariate logistic regression model was established and the risk of polymyxin B-associated AKI were predicted by a receiver operating characteristic curve, with maximal Youden index used to identify safety thresholds among the study population. RESULTS: Fifty-four adult patients were included in the study. AKI was detected in 14 patients during polymyxin B treatment (25.9%, 14 out of 54). Cmin (odds ratio [OR] 2.071; 95% confidence interval [CI] 1.235-3.472) and baseline serum creatinine (OR 1.024; 95% CI 1.005-1.043) were significant independent risk factors for developing AKI. The area under the ROC curve of the combined predictor was larger based on the above factors. When the Youden index was at maximum, the optimal cut-off point was 6.678 of the ROC curve. When Cmin ≥ 3.13 mg/L, the probability of AKI was more than 50%. CONCLUSION: In this study, when the calculated combined predictor value was >6.678, there was an increased risk of AKI. Maintaining a polymyxin B Cmin level below 3.13 mg/L may be helpful in reducing the incidence of polymyxin B associated nephrotoxicity.

Model Based Identification of Linezolid Exposure-toxicity Thresholds in Hospitalized Patients.

Evidence supports linezolid therapeutic drug monitoring as the exposure-response relationship has been identified for toxicity among patients receiving linezolid, but the data to establish the upper limit are limited and the published toxicity thresholds range widely. The purpose of this study was to determine the linezolid exposure-toxicity thresholds to improve the safety of linezolid. This is a multicenter retrospective study of adult patients treated with linezolid from 2018 to 2019. The population pharmacokinetic model of linezolid was established based on 270 plasma concentrations in 152 patients, which showed creatinine clearance and white cell count are covariates affecting the clearance of linezolid, and serum albumin is the covariate affecting the volume of distribution. Classification and regression tree analysis was used to determine the linezolid exposure thresholds associated with an increased probability of toxicity. Among 141 patients included for toxicity analysis, the rate of occurring toxicity was significantly higher among patients with an AUC0-24, d1 ≥163 mg h/L, AUC0-24, d2 ≥207 mg h/L, AUC0-24, ss ≥210 mg h/L, and Cmin,d2 ≥6.9 mg/L, Cmin,ss ≥6.9 mg/L, while no threshold was discovered for Cmin, d1. Those exposure thresholds and duration of linezolid treatment were independently associated with linezolid-related toxicity in the logistic regression analyses. In addition, the predictive performance of the AUC0-24 and Cmin thresholds at day 2 and steady state were close. Considering that the AUC estimation is cumbersome, Cmin threshold at 48 h and steady state with a value of ≥6.9 mg/L is recommended to improve safety, especially for patients with renal insufficiency and patients with low serum albumin.

Lovastatin Prevents Depressive Behaviors and Increased Hippocampal Neurogenesis in Streptozotocin-Induced Diabetic Mice.

Depression is a progressive and chronic syndrome and commonly related to several neuropsychiatric comorbidities, of which depression is the most studied. Population-based studies have suggested a positive role of statins in ameliorating depression risk. However, the role of statins in the treatment of diabetes-related depression has not been well examined. Herein, we investigated the effects of lovastatin (LOV) on depressive phenotypes in streptozotocin-induced diabetic mice. The data suggested that the treatment of LOV at 10 or 20 mg/kg for 3 weeks markedly prevented diabetes-associated depressive behaviors reflected by better performance in the sucrose preference test, tail suspension test, and novelty-suppressed feeding test. The study further showed that these treatments improved the hippocampal neurogenesis as evidenced by increased bromodeoxyuridine-positive cells in the dentate gyrus with higher expression of mature brain-derived neurotrophic factor and increased phosphorylation of cAMP-response element-binding protein. As expected, diabetic mice treated with LOV showed significant improvement of hyperlipidemia rather than hyperglycemia. These results suggest that LOV may be employed as a drug for the treatment of diabetes-related depression.