Clinical Experience with Off-Label Intrathecal Administration of Selected Antibiotics in Adults:An Overview with Pharmacometric Considerations

Drain-associated intracerebral infections are life-threatening emergencies. Their treatment is challenging due to the limited penetration of antibiotics to the site of infection, resulting in potentially inadequate exposure. The emergence of multidrug-resistant pathogens might force the use of off-label intrathecal (IT) doses of antibiotics. We reviewed the literature on general aspects determining intrathecal dosing regimen, using pharmacometric knowledge. We summarised clinical experience with IT doses of antibiotics that are usually not used intrathecally, as well as the outcome of the cases and concentrations reached in the cerebrospinal fluid (CSF). Factors determining the IT regimen are the size of the ventricle system and the CSF drainage volume. With regard to pharmacometrics, pharmacokinetic/pharmacodynamic indices are likely similar to those in non-cerebral infections. The following number (N) of cases were described: benzylpenicillin (&gt;50), ampicillin (1), ceftazidime (2), cephaloridine (56), ceftriaxone (1), cefotiam (1), meropenem (57), linezolid (1), tigecycline (15), rifampicin (3), levofloxacin (2), chloramphenicol (3) and daptomycin (8). Many side effects were reported for benzylpenicillin in the 1940–50s, but for the other antibiotics, when administered correctly, all side effects were minor and reversible. These data might help when choosing an IT dosing regimen in case there is no alternative option due to antimicrobial resistance.</p

DiffErenCes in AntihypertenSive Drug Blood Levels in Patients with HypertensiON (DECISION):Protocol for a Prospective Observational Study Comparing Pharmacokinetics and Pharmacodynamics Between Young and Elderly Patients

Adequate controlled blood pressure decreases the risk of cardiovascular events. However, the elderly are more vulnerable and thereby more prone to side effects of antihypertensive drugs. A lack of pharmacokinetic and pharmacodynamic (PK/PD) studies in older patients makes specific and tailored advices towards antihypertensive drug therapy difficult. The aim of our study, DiffErenCes In antihypertenSive drug levels In patients with hypertensiON (DECISION), is to fill in this PK/PD knowledge gap and move towards precision dosing. DECISION is a prospective observational PK/PD study set up to determine the difference in exposure to the antihypertensive drugs, losartan and perindopril, measured by drug levels in blood. The area under the curve (AUC; PK) and furthermore the association between the AUC and the effect on blood pressure (PD) will be compared between elderly and younger patients

Stability of 10 Beta-Lactam Antibiotics in Human Plasma at Different Storage Conditions

BACKGROUND: Recently, several studies have assessed the effects of therapeutic drug monitoring of frequently prescribed beta-lactam antibiotics, for which they were quantified in human plasma samples. Beta-lactams are considered unstable, leading to extra challenges in quantification. Therefore, to ensure sample stability and minimize sample degradation before analysis, stability studies are crucial. This study investigated the stability of 10 frequently used beta-lactam antibiotics in human plasma at relevant storage conditions for clinical use. METHODS: Amoxicillin, benzylpenicillin, cefotaxime, ceftazidime, ceftriaxone, cefuroxime, flucloxacillin, imipenem, meropenem, and piperacillin were analyzed using ultraperformance convergence chromatography tandem mass spectrometry and liquid chromatography tandem mass spectrometry. Their short-term and long-term stabilities were investigated by measuring quality control samples at low and high concentrations against freshly prepared calibration standards. Measured concentrations at each time point were compared with the concentrations at T = 0. Antibiotics were considered stable if recovery results were between 85% and 115%. RESULTS: Short-term stability results indicated ceftriaxone, cefuroxime, and meropenem to be stable up to 24 hours at room temperature. All evaluated antibiotics, except imipenem, were stable on ice in a cool box for 24 hours. Amoxicillin, benzylpenicillin, and piperacillin were stable for 24 hours at 4-6°C. Cefotaxime, ceftazidime, cefuroxime, and meropenem were stable at 4-6°C up to 72 hours. Ceftriaxone and flucloxacillin were stable for 1 week at 4-6°C. Long-term stability results showed that all antibiotics were stable up to 1 year at -80°C, except imipenem and piperacillin, which were stable for 6 months at -80°C. CONCLUSIONS: Plasma samples for amoxicillin, benzylpenicillin, cefotaxime, ceftazidime, flucloxacillin, and piperacillin may be stored for a maximum of 24 hours in a cool box. Refrigeration is suitable for plasma samples of amoxicillin, benzylpenicillin, meropenem, and piperacillin for up to 24 hours and cefotaxime, ceftriaxone, ceftazidime and cefuroxime for 72 hours. Plasma samples for imipenem should be frozen directly at -80°C. For long-term storage, plasma samples can be stored at -80°C for a maximum of 6 months for imipenem and piperacillin and 12 months for all other evaluated antibiotics.</p

The Pharmacokinetics of Beta-Lactam Antibiotics Using Scavenged Samples in Pediatric Intensive Care Patients:The EXPAT Kids Study Protocol

Background: Emerging evidence supports the importance of optimized antibiotic exposure in pediatric intensive care unit (PICU) patients. Traditional antibiotic dosing is not designed for PICU patients, as the extreme pharmacokinetic (PK) behavior of drugs threatens the achievement of optimal antibiotic treatment outcomes. Scavenged sampling is a sampling strategy which may have positive implications for routine TDM and PK research, as well as monitoring other biomarkers. EXPAT Kids study was designed to analyze whether current empiric dosing regimens of frequently used beta-lactam antibiotics achieve defined therapeutic target concentrations in PICU patients. Methods: A mono-centre, exploratory pharmacokinetic and pharmacodynamic study was designed to assess target attainment of beta-lactam antibiotics. One hundred forty patients will be included within 24 months after start of inclusion. At various time points serum concentration of the study antibiotic (cefotaxime, ceftazidime, ceftriaxone, cefuroxime, flucloxacillin, and meropenem) are determined. In parallel with these sampling moments, residual material is collected to validate the use of blood of scavenged heparinized astrup syringes for the quantification of antibiotic exposure. The primary outcome is the time that the free (unbound) concentration of the study antibiotic remains above one to four the minimal inhibitory concentration during a dosing interval (100%ƒT > MIC and 100%ƒT>4xMIC). Other included outcomes are disease severity, safety, length of stay, and inflammatory biomarkers. Discussion: Potentially, scavenged sampling may enrich the EXPAT Kids dataset, and reduce additional blood sampling and workload for clinical personnel. The findings from the EXPAT Kids study will lead to new insights in the PK parameters of beta-lactams and consecutive effects on target attainment and clinical outcomes. Is there a need for more precision in dosing? Netherlands Trial Register Number: Trial NL9326

Screening for hazardous alcohol use in the Emergency Department:Comparison of phosphatidylethanol with the Alcohol Use Disorders Identification Test and the Timeline Follow-back

Background: Up to 15% of all visits to the Emergency Department (ED) are alcohol related. Identification of problematic alcohol use is important in this setting because it allows for intervention and prevention efforts. This study investigated the correlation between the objective phosphatidylethanol (PEth) marker and the subjective Alcohol Use Disorders Identification Test (AUDIT) and Timeline Followback Questionnaire (TLFB) as screening methods for hazardous alcohol use in the general ED population. Methods: This prospective cohort study included 301 ED patients (57% male) who were seen in the ED and required to give a blood sample. The correlation between the values of PEth (PEth 16:0/18:1 and PEth 16:0/18:2) and the scores on the AUDIT and TLFB were analyzed using Spearman's rank correlation coefficient. Differences between risk categories of PEth and AUDIT were also examined. Results: The Spearman correlation coefficients between PEth 16:0/18:1|PEth 16:0/18:2 values and the AUDIT scores were moderate (PEth 16:0/18:1: 0.67, p < 0.001; PEth 16:0/18:2: 0.67, p < 0.001). Of the patients who scored ‘low risk drinking/abstinence’ according to the AUDIT questionnaire, respectively 1% and 4% had PEth 16:0/18:1|PEth 16:0/18:2 values indicating excessive alcohol use, and another 10% and 12% had PEth 16:0/18:1|PEth 16:0/18:2 values indicating moderate alcohol consumption. Of the 12 (PEth 16:0/18:1) and 25 (PEth 16:0/18:2) patients with high-risk values, respectively 25% and 40% scored in the lowest risk category on the AUDIT questionnaire. Spearman correlation coefficients between PEth 16:0/18:1|PEth 16:0/18:2 values and TLFB two-week scores were high (PEth 16:0/18:1: 0.74, p < 0.001; PEth 16:0/18:2: 0.82, p < 0.001). Conclusions: AUDIT scores were moderately correlated with PEth values in the general ED population. In almost all cases where there was not a good correlation, patients had high PEth values with low AUDIT scores. We conclude that PEth identifies patients with problematic alcohol use who are missed by the AUDIT questionnaire and therefore PEth could be used as an additional screening method for hazardous alcohol use in this population

Dried blood spot analysis for the quantification of vancomycin and creatinine using liquid chromatography – tandem mass spectrometry:Method development and validation

Background: Vancomycin is a widely used antibiotic for the treatment of gram-positive bacterial infections, especially for methicillin-resistant Staphylococcus aureus (MRSA) infections. Due to a small therapeutic range and large inter-patient variability, therapeutic drug monitoring (TDM) of vancomycin is required to minimize toxicity and maximize treatment efficacy. Venous blood sampling is mostly applied for TDM of vancomycin, although this widely used sampling method is more invasive compared to less painful alternatives, such as the dried blood spot (DBS) method, which can be performed at home. Method: We developed an UPLC-MS/MS method for the quantification of vancomycin and creatinine in DBS. A fast sample preparation and short analysis run time of 5.2 min were applied, which makes this method highly suitable for clinical settings. Validation was performed according to international (FDA and EMA) guidelines. Results: The validated concentration range was found linear for creatinine from 41.8 µmol/L to 722 µmol/L and for vancomycin from 3.8 mg/L to 76.6 mg/L (r2 &gt; 0.990) and the inaccuracies, imprecisions, hematocrit effects, and recoveries were &lt; 15 % for both compounds. No significant carryover effect was observed. Conclusion: Hence, we successfully validated a quantification method for the simultaneous determination of creatinine and vancomycin in DBS.</p

Which patients benefit from model-informed precision dosing of beta-lactam antibiotics and ciprofloxacin at the ICU?

Objectives: Antibiotic dosing is not optimal in the ICU. Our recent trial investigated the effect of model-informed precision dosing (MIPD) of beta-lactam antibiotics and ciprofloxacin and showed no significant differences in clinical outcomes in all patients. This study aimed to identify subgroups of patients in which the MIPD of these antibiotics could be beneficial for clinical outcomes. Methods: We analysed data from the DOLPHIN randomized controlled trial, which compared MIPD to standard dosing of beta-lactam antibiotics and ciprofloxacin in 388 ICU patients. We divided patients into subgroups based on baseline characteristics and assessed the effect of MIPD on 28-day mortality, 6-month mortality, change in sequential organ failure assessment (delta-SOFA), and ICU length of stay (LOS). Results: We found a lower 28-day mortality in patients with a SOFA below 8 randomized to MIPD (OR 0.40; 95% CI 0.17–0.88). However, patients with a higher SOFA show an increased 28-day mortality (OR 1.94; 95% CI 1.07–3.59) in the MIPD group. ICU LOS was increased in patients receiving MIPD with a SOFA below 8 (IRR 1.36; 95% CI 1.01–1.83) and those receiving MIPD for ceftriaxone (IRR 1.76; 95% CI 1.24–2.51). Patients receiving a dose recommendation within 24 hours show a trend towards decreased ICU LOS (IRR 0.77; 95% CI 0.52–1.16) and higher delta-SOFA (estimate -1.19; 95% CI -2.98–0.60). Conclusions: ICU patients with a SOFA below 8 using MIPD had an increased ICU LOS but a lower 28-day mortality. Fast dose recommendations using MIPD of beta-lactam antibiotics and ciprofloxacin needs to be investigated in ICU patients.</p

Population plasma and urine pharmacokinetics and the probability of target attainment of fosfomycin in healthy male volunteers

Purpose: A population pharmacokinetic model of fosfomycin was developed in healthy volunteers after intravenous administration, and different dosing regimens were evaluated in terms of the probability of target attainment for Escherichia coli using both plasma and urinary pharmacokinetic/pharmacodynamic targets. Methods: Eight healthy men received fosfomycin as both intermittent 8 g q8h and continuous infusion 1 g/h with a loading dose of 8 g in a crossover study design. Dense sampling was conducted during both regimens. Population pharmacokinetic modelling was performed using NONMEM. Monte Carlo simulations were conducted to evaluate the Probability of Target Attainment (PTA) of different dosing regimens using bactericidal (AUC24h/MIC of 83 and 75%T&gt;MIC) and bacteriostatic (AUC24h/MIC of 25) plasma targets and bacteriostatic (AUC24h/MIC of 3994) urine target. Results: A total of 176 plasma and 86 urine samples were available for PK analysis. A two-compartment model with a urine compartment best described the data. Glomerular filtration rate (GFR) showed a significant correlation with renal clearance and was implemented in the final model. Simulation results show that the dose of 4 g q8h reached 100% of PTA using bactericidal and bacteriostatic targets for MIC up to 16 mg/L. Conclusion: For the clinical breakpoint of 32 mg/L, the standard dosing regimen (4 g q8h) might not be sufficient to reach the bactericidal target. Higher dosing of 8 g q8h as an intermittent infusion or 0.75 g/h as a continuous infusion might be required. Continuous infusion resulted in better attainment of the %T&gt;MIC target than intermittent infusion.</p

Pursuing the Real Vancomycin Clearance during Continuous Renal Replacement Therapy in Intensive Care Unit Patients:Is There Adequate Target Attainment?

Introduction: Vancomycin is used in intensive care unit (ICU) patients for the treatment of infections caused by gram-positive bacteria. The vancomycin pharmacokinetic/pharmacodynamic index is a ratio of the area under the concentration to the minimum inhibitory concentration ≥400-600 h∗mg/L. This target can generally be achieved by a plasma concentration of 20-25 mg/L. Together with the pathophysiological alterations and pharmacokinetic variability associated with critical illness, the use of continuous renal replacement therapy (CRRT) may complicate the attainment of adequate vancomycin concentrations. The primary objective was the prevalence of attainment of vancomycin concentrations 20-25 mg/L after 24 h in adult ICU patients receiving CRRT. Secondary outcomes were to evaluate target attainment at days 2 and 3 and to calculate vancomycin clearance (CL) by CRRT and residual diuresis. Methods: We performed a prospective observational study in adult ICU patients on CRRT, which received at least 24 h continuous infusion of vancomycin. Between May 2020 and February 2021, daily vancomycin residual blood gas and dialysate samples were collected from 20 patients, every 6 h and if possible vancomycin urine samples. Vancomycin was analysed with an immunoassay method. The CL by CRRT was calculated by a different approach correcting for the downtime and providing insight into the degree of filter patency. Results: The proportion of patients with vancomycin concentrations &lt;20 mg/L was 50% 24 h after starting vancomycin (n = 10). No differences were observed in patient characteristics. The target vancomycin concentration 20-25 mg/L was only achieved in 30% of the patients. On days 2 and 3, despite the use of TDM and albeit in lower percentages, sub- and supratherapeutic levels were still observed. Taking downtime and filter patency into account resulted in lower vancomycin CL. Conclusions: 50% of the studied ICU patients on CRRT showed subtherapeutic vancomycin concentrations 24 h after starting therapy. The results reveal that optimization of vancomycin dosage during CRRT therapy is needed.</p

The Clearance of Midazolam and Metabolites during Continuous Renal Replacement Therapy in Critically Ill Patients with COVID-19

Introduction: Midazolam-based continuous intravenous sedation in patients admitted to the intensive care unit (ICU) was a necessity during the COVID-19 pandemic. However, benzodiazepine-based sedation is associated with a high incidence of benzodiazepine-related delirium and additional days on mechanical ventilation. Due to the requirement of high midazolam doses in combination with the impaired renal clearance (CL) of the pharmacological active metabolite 1-OH-midazolam-glucuronide (10% compared to midazolam), ICU patients with COVID-19 and continuous renal replacement therapy (CRRT) were at risk of unintended prolonged sedation. Several CRRT-related factors may have influenced the delivered CL of midazolam and its metabolites. Therefore, the aim of the study was to identify and describe these CRRT-related factors. Methods: Pre-filter blood samples and ultrafiltrate samples were collected simultaneously. Midazolam, 1-OH-midazolam, and 1-OH-midazolam-glucuronide plasma samples were analyzed using an UPLC-MS/MS method. The prescribed CRRT dose was corrected for downtime and filter integrity using the urea ratio (urea concentration in effluent/urea concentration plasma). CL of midazolam and its metabolites were calculated with the delivered CRRT dose (corrected for downtime and saturation coefficient [SD]). Results: Three patients on continuous venovenous hemodialysis (CVVHD) and 2 patients on continuous venovenous hemodiafiltration (CVVHDF) were included. Midazolam, 1-OH-midazolam, and 1-OH-midazolam-glucuronide concentrations were 2,849 (0-6,700) μg/L, 153 (0-295) μg/L, and 27,297 (1,727-39,000) μg/L, respectively. The SD was 0.03 (0.02-0.03) for midazolam, 0.05 (0.05-0.06) for 1-OH-midazolam, and 0.33 (0.23-0.43) for 1-OH-midazolam-glucuronide. The delivered CRRT CL was 1.4 (0-1.7) mL/min for midazolam, 2.7 (0-3.5) mL/min for 1-OH-midazolam, and 15.7 (4.0-27.7) mL/min for 1-OH-midazolam-glucuronide. Conclusions: Midazolam and 1-OH-midazolam were not removed during CVVHD and CVVHDF. However, 1-OH-midazolam-glucuronide was removed reasonably, approximately up to 43%. CRRT modality, filter integrity, and downtime affect this removal. These data imply a personalized titration of midazolam in critically ill patients with renal failure and awareness for the additional sedative effects of its active metabolites.</p