Changes of colistin pharmacokinetics in critically ill patients due to the extracorporeal membrane oxygenation: protocol for the COL-ECMO2022 trial - a prospective, non-randomised, open-label phase IV pharmacokinetic clinical trial.

INTRODUCTION: Colistin is a lipopeptide antibiotic administered as an inactive prodrug-colistin methanesulfonate (CMS). Colistin is a drug with a narrow therapeutic window; the limiting factors are mainly nephrotoxicity and neurotoxicity, dependent on plasma concentrations. The number of patients with infections caused by multidrug-resistant Gram-negative bacteria sensitive only to colistin and the number of patients requiring extracorporeal membrane oxygenation (ECMO) support for severe respiratory failure increased significantly in association with COVID-19-induced infections. ECMO can generally affect the pharmacokinetics of drugs by creating a new compartment. METHODS AND ANALYSIS: The COL-ECMO2022 study is a prospective, non-randomised, single-centre, phase IV pharmacokinetic clinical trial designed to assess the influence of ECMO on the pharmacokinetics of colistin and CMS. Up to 30 patients treated with colistin will be included in the study and assigned to one of two arms, depending on the presence/absence of ECMO. All study participants will receive standard CMS dose intravenously. The plasma concentrations of colistin and CMS taken at defined intervals will be assessed by high-performance liquid chromatography-mass spectrometry. Patients will participate in the clinical trial for a maximum of three monitored dosing intervals. A population pharmacokinetic model will be developed to assess the influence of ECMO on pharmacokinetics. A difference greater than 25% is considered clinically significant. ETHICS AND DISSEMINATION: The study has been approved by the Ethics Committee of St. Anne's University Hospital Brno (Number 10ML/2022-AM). Related manuscripts will be submitted to peer-review journals. TRIAL REGISTRATION NUMBERS: EudraCT Number 2022-000291-19; NCT05542446.

Challenges of Colistin Use in ICU and Therapeutic Drug Monitoring: A Literature Review.

The emerging resistance of Gram-negative bacteria is a growing problem worldwide. Together with the financial cost, limited efficacy, and local unavailability of newer antibiotics or their combinations, it has led to the reintroduction of colistin as a therapeutic alternative. Despite its protracted development and availability on the market, there is now a complex maze of questions surrounding colistin with a more or less straightforward relationship to its safety and efficacy. This review aims to offer a way to navigate this maze. We focus on summarizing the available literature regarding the use of colistin in critically ill patients, particularly on stability, pharmacokinetics, methods for determining plasma concentrations, and therapeutic drug monitoring benefits and limitations. Based on these data, we then highlight the main gaps in the available information and help define directions for future research on this drug. The first gap is the lack of data on the stability of intravenous and nebulization solutions at clinically relevant concentrations and under external conditions corresponding to clinical practice. Furthermore, pharmacokinetic-pharmacodynamic parameters should be validated using standardized dosing, including a loading dose. Based on the pharmacokinetic data obtained, a population model for critically ill patients should be developed. Finally, the interference of colistin with extracorporeal methods should be quantified.

Population pharmacokinetic model-based dosing proposal for ampicillin prophylaxis in cardiac surgery patients with cardiopulmonary bypass.

The aim of this study was to describe and quantify pharmacokinetics of ampicillin used prophylactically in cardiac surgery both with and without cardiopulmonary bypass (CPB) using population pharmacokinetic analysis in order to propose an optimal dosing strategy. Adult patients undergoing cardiac surgery and treated with prophylactic dose of 2 g ampicillin were enrolled to this prospective study. Blood samples were collected according to the study protocol and ampicillin plasma concentrations were measured using HPLC/UV system. A three-stage population pharmacokinetic model using nonlinear mixed-effects modelling approach was developed. Totally 273 blood samples obtained from 20 patients undergoing cardiac surgery with the use of the CPB and 20 patients without CPB use were analyzed. Two-comparmental model best fits ampicillin concentration-time data. Mean ± SD body weight-normalized ampicillin central and peripheral volume of distribution was 0.12 ± 0.02 L/kg and 0.15 ± 0.03 L/kg, respectively, while mean ± SD ampicillin clearance in typical patient with eGFR of 1.5 mL/s/1.73 m2 was 1.17 ± 0.05 L/h. The use of CPB did not significantly affect the pharmacokinetics of ampicillin. When administering 2 g of ampicillin before surgery, an additional dose should be administered to reach the PK/PD target of fT > MIC = 50% if the operation lasts longer than 430 min in patients with moderate to severe renal impairment, 320 min in patients with mild renal impairment, 220 min in patients with normal renal function status or 140 min in patients with an augmented renal clearance.

Population pharmacokinetics of three alternative prophylactic antibiotics during cardiac surgery with extracorporeal circulation.

AIMS: The aim of this pharmacokinetic study was to describe and quantify population pharmacokinetics of three antibiotics, cefazolin, ampicillin, and ciprofloxacin, used as antibacterial prophylaxis during cardiovascular surgery with the use of extracorporeal circulation (ECC). METHODS: Adult patients undergoing cardiac surgery with ECC were enrolled to this prospective, pharmacokinetic study. An intravenous bolus of 2 g of ampicillin, 2 g of cefazolin or 400 mg of ciprofloxacin was administered 60-30 min before surgery. Blood samples were collected at 15, 30, 45, 60, 120 and 180 min after the administration and at the end of the surgery. Plasma concentrations of the antibiotics were measured using HPLC methods. Serum concentration-time profiles were analyzed using nonlinear mixed-effects modeling approach. RESULTS: A total of 54 patients were enrolled into the study, 20 with ampicillin, 25 cefazolin and 9 ciprofloxacin. For all antibiotics, population pharmacokinetic models have been successfully developed. CONCLUSION: We identified estimated glomerular filtration rate (eGFR) as the main factor determining the achievement of the pharmacokinetic/pharmacodynamic (PK/PD) target in ampicillin or cefazolin and body weight in ciprofloxacin prophylaxis during cardiac surgery with ECC support.

[Pharmacological properties of colistin].

Colistin is a narrow-spectrum lipopeptide antimicrobial agent used to treat nosocomial infections caused by multidrug-resistant bacteria, especially in critically ill patients and those with cystic fibrosis. Colistin represents a concentration-time-dependent antibiotic with highly variable pharmacokinetics related to the heterogeneity of the target population and the necessity of bioactivation. Colistin is administered as the inactive prodrug colistimethate sodium. Nephrotoxicity and neurotoxicity are the most frequent adverse effects.

Population Pharmacokinetics of Prophylactic Cefazolin in Cardiac Surgery with Standard and Minimally Invasive Extracorporeal Circulation.

The objectives of this study were to develop a population pharmacokinetic model of prophylactically administered cefazolin in patients undergoing cardiac surgery with and without the use of the cardiopulmonary bypass of both existing types-standard (ECC) and minimallyu invasive extracorporeal circulation (MiECC)-and to propose cefazoline dosing optimization based on this model. A total of 65 adult patients undergoing cardiac surgery were recruited to this clinical trial. A prophylactic cefazolin dose of 2 g was intravenously administered before surgery. Blood samples were collected using a rich sampling design and cefazolin serum concentrations were measured using the HPLC/UV method. The pharmacokinetic population model was calculated using a nonlinear mixed-effects modeling approach, and the Monte Carlo simulation was used to evaluate the PK/PD target attainment. The population cefazolin central volume of distribution (Vd) of 4.91 L increased by 0.51 L with each 1 m2 of BSA, peripheral Vd of 22.07 L was reduced by 0.77 L or 0.79 L when using ECC or MiECC support, respectively, while clearance started at 0.045 L/h and increased by 0.49 L/h with each 1 mL/min/1.73 m2 of eGFR. ECC/MiECC was shown to be covariate of cefazolin Vd, but without relevance to clinical practice, while eGFR was most influential for the PK/PD target attainment. The standard dose of 2 g was sufficient for PK/PD target attainment throughout surgery in patients with normal renal status or with renal impairment. In patients with augmented renal clearance, an additive cefazolin dose should be administered 215, 245, 288 and 318 min after the first dose at MIC of 4, 3, 2 and 1.5 mg/L, respectively.

[Ciprofloxacin: pharmacokinetics and a potential for therapeutic monitoring].

Ciprofloxacin is a broad-spectrum bactericidal antibiotic with a concentration-dependent antimicrobial effect. Ciprofloxacin penetrates well into tissues, providing good efficacy against many Gram-negative microorganisms. Due to its good antibacterial efficacy and tolerability, it is often used in the treatment of critically ill. However, high interindividual variability in pharmacokinetics is reported in this population, especially in volume of distribution, clearance, and elimination half-life. Interindividual variability across patient groups results in difficult achievement of the therapeutic goal, mostly described as AUC/MIC ≥ 125. The usual dosing is 400 mg after 8-12 hours intravenously for one hour. In critically ill patients, the lower dose proved to be insufficient. In these patients, doses of at least 1 200 mg/day are required. An initial dose of 800 mg increases the probability of achieving the therapeutic goal by 35-45 %. Although many authors mention the possibility of using therapeutic drug monitoring to achieve the therapeutic goal, there are only few trials describing its benefits.