Are higher vancomycin doses needed in venticle-external shunted patients?

Application of therapeutic drug monitoring to the treatment of bacterial central nervous system infection: a scoping review

BACKGROUND

Bacterial central nervous system (CNS) infection is challenging to treat and carries high risk of recurrence, morbidity, and mortality. Low CNS penetration of antibiotics may contribute to poor clinical outcomes from bacterial CNS infections. The current application of therapeutic drug monitoring (TDM) to management of bacterial CNS infection was reviewed.

METHODS

Studies were included if they described adults treated for a suspected/confirmed bacterial CNS infection and had antibiotic drug concentration(s) determined that affected individual treatment.

RESULTS

One-hundred-and-thirty-six citations were retrieved. Seventeen manuscripts were included describing management of 68 patients. TDM for vancomycin (58/68) and the beta-lactams (29/68) was most common. Timing of clinical sampling varied widely between studies and across different antibiotics. Methods for setting individual PK-PD targets, determining parameters and making treatment changes varied widely and were sometimes unclear.

DISCUSSION

Despite increasing observational data showing low CNS penetration of various antibiotics, there are few clinical studies describing practical implementation of TDM in management of CNS infection. Lack of consensus around clinically relevant CSF PK-PD targets and protocols for dose-adjustment may contribute. Standardised investigation of TDM as a tool to improve treatment is required, especially as innovative drug concentration-sensing and PK-PD modelling technologies are emerging. Data generated at different centres offering TDM should be open access and aggregated to enrich understanding and optimize application.

Efficacy of Vancomycin and Meropenem in Central Nervous System Infections in Children and Adults: Current Update

The current antimicrobial therapy of bacterial infections of the central nervous system (CNS) in adults and pediatric patients is faced with many pitfalls as the drugs have to reach necessary levels in serum and cross the blood-brain barrier. Furthermore, several studies report that different factors such as the structure of the antimicrobial agent, the severity of disease, or the degree of inflammation play a significant role. Despite the available attempts to establish pharmacokinetic (PK) modeling to improve the required dosing regimen for adults and pediatric patients, conclusive recommendations for the best therapeutic strategies are still lacking. For instance, bacterial meningitis, the most common CNS infections, and ventriculitis, a severe complication of meningitis, are still associated with 10% and 30% mortality, respectively. Several studies report on the use of vancomycin and meropenem to manage meningitis and ventriculitis; therefore, this review aims to shed light on the current knowledge about their use in adults and pediatric patients. Consequently, studies published from 2015 until mid-July 2021 are included, and data about the study population, levels of drugs in serum and cerebrospinal fluid (CSF), and measured PK data in serum and CSF are provided. The overall aim is to provide the readers a recent reference that summarizes the pitfalls and success of the current therapy and emphasizes the importance of performing more studies to improve the clinical outcome of the current therapeutical approach.

Pharmacokinetics of Favipiravir in Critically Ill Patients With COVID-19

Since December 2019, a novel coronavirus (severe acute respiratory syndrome‐coronavirus 2 (SARS‐CoV‐2)) infection has been rapidly spreading worldwide and causing the respiratory illness, coronavirus disease 2019 (COVID‐19). The antiretroviral drug favipiravir (FPV) has been experimentally used for COVID‐19 treatment since March 2020 in Japan. However, the pharmacokinetics of FPV in critically ill patients is unknown. We measured the serum concentration of FPV using high‐performance liquid chromatography in patients with severe COVID‐19 who were admitted to the intensive care unit and placed on mechanical ventilation. The patients were administered 1,600 mg of FPV twice daily on day 1, followed by 600 mg twice daily from day 2 to day 5 (or more if needed). Suspensions of FPV tablets were administered through a nasogastric tube. Seven patients were enrolled in this study. Forty‐nine blood samples were obtained from the eligible patients to evaluate FPV concentration. The FPV trough (after 8–12 hours) concentrations of most samples were lower than the lower limit of quantification (1 µg/mL) and half‐maximal effective concentration (9.7 µg/mL) against SARS‐CoV‐2 previously tested in vitro. FPV trough concentration in critically ill patients was much lower than that of healthy subjects in a previous clinical trial, which is a cause for great concern. Further study is required to determine the optimal strategy for treatment of patients with severe COVID‐19.

Influence of cerebrospinal fluid drainage and other variables on the plasma vancomycin trough levels in postoperative neurosurgical patients

BACKGROUND

Therapeutic drug monitoring (TDM) aims to minimise the clinical impact of vancomycin (VCM) pharmacokinetic variability. However, TDM data are limited among specific patient populations, including postoperative neurosurgical populations. The objective of this study was to retrospectively investigate the influence of cerebrospinal fluid (CSF) drainage and other factors on the serum trough concentrations of VCM.

METHODS

We analysed 154 patients who had been hospitalised in the neurosurgical ward and received intravenous infusions of VCM. We compared the daily doses of VCM, serum VCM concentrations, and serum concentration/dose ratio (C/D ratio) between patients who underwent CSF drainage (drainage group) and controls (nondrainage group). In addition, we also elucidated other factors affecting the attainment of target concentrations.

RESULTS

The patients in the drainage group showed a significantly lower trough concentration of VCM (6.2 ± 4.2 µg/mL) than that shown by the nondrainage group (8.5 ± 6.6 µg/mL, p = 0.03). Furthermore, the patients in the drainage group showed a significantly different trough C/D ratio (3.1 ± 2.1) than that shown by the nondrainage group (4.3 ± 3.4, p = 0.014). The Mann-Whitney U test demonstrated significantly lower VCM trough levels with concomitant use of diuretic than without (p = 0.004). Multivariable logistic regression demonstrated that coadministered diuretic independently predicted subtherapeutic trough levels of <10 µg/mL (p = 0.04). The concomitant use of albumin and other variables exerted no effects on VCM trough levels.

CONCLUSIONS

These data suggest that CSF drainage and diuretics have different effects, but it seems that both lower the VCM concentration in postoperative neurosurgical patients. Our findings strongly suggest that a high dose of VCM is required to maintain optimal serum concentrations of VCM in patients managed with CSF drainage or concomitant use of diuretic.

Intrathecal penetration of meropenem and vancomycin administered by continuous infusion in patients suffering from ventriculitis-a retrospective analysis

BACKGROUND

Vancomycin and meropenem are frequently used as empiric treatment for ventriculitis. Penetration into the cerebrospinal fluid (CSF) depends on various factors with a high inter-individual variability. Because attaining and maintaining adequate concentrations of meropenem and vancomycin in the CSF is crucial for their bactericidal effect, we introduced a routine therapeutic drug monitoring (TDM) from CSF and serum for both antibiotics. We studied the antibiotic penetration into the CSF.

METHODS

Patient data including serum and CSF concentrations for meropenem and vancomycin were collected in a retrospective fashion. Antibiotic CSF penetration ratio was calculated for each patient. Antibiotics were administered by continuous infusion aiming for serum target concentrations of 20-30 mg/L for vancomycin and 16-32 mg/L for meropenem.

RESULTS

Twenty-two patients with 36 CSF/serum pairs for meropenem and 43 pairs for vancomycin were studied. No patient suffered from renal or liver insufficiency. Mean vancomycin serum concentration was 22 ± 8 mg/L and the mean CSF concentration 4.5 ± 2.6 mg/L. CSF penetration was 20 ± 11% (coefficient of determination (R²) 0.02). For meropenem, the mean serum concentration was 30.7 ± 14.9 mg/L, mean CSF concentration 5.5 ± 5.2 mg/L, and a penetration of 18 ± 12%, R² = 0.42.

CONCLUSION

Penetration of meropenem and vancomycin into the CSF is low while showing a high interindividual variability. Various patients in our study cohort were at risk for insufficient target attainment in CSF. Continuous administration of antibiotics under routine TDM appears to be a feasible and reasonable approach for optimization of intrathecal drug levels in patients suffering from ventriculitis. TDM might guide individual dosing adaptation and efforts to predict the CSF penetration of meropenem and vancomycin in cases of ventriculitis.

A Randomized Pharmacokinetic and Pharmacodynamic Evaluation of Every 8-Hour and 12-Hour Dosing Strategies of Vancomycin and Cefepime in Neurocritically ill Patients

PURPOSE

Neurocritically ill patients have clinically significant alterations in pharmacokinetic parameters of renally eliminated medications that may result in subtherapeutic plasma and cerebrospinal fluid antibiotic concentrations.

METHODS

We conducted a prospective randomized open-label study of adult neurocritically ill patients treated with vancomycin and cefepime. Vancomycin 15 mg/kg and cefepime 2 g were dosed at every-8- or 12-hour intervals. The primary outcomes were the achievement of pharmacodynamic (PD) targets related to time of unbound drug above minimum inhibitory concentrations (MIC) for 60% or more of the dosing interval (fT > MIC ≥ 60%) for β-lactams and ratio of 24-hour area under the curve (AUC):MIC of 400 or greater for vancomycin.

RESULTS

Twenty patients were included in the study. They were divided equally between the every-12-hour and every-8-hour dosing groups. Patients (mean age 51.8 ± 11 yrs) were primarily male (60%) and white (95%), and most had an admission diagnosis of intracranial hemorrhage (80%). Compared with the every-12-hour group, the every-8-hour vancomycin group achieved target trough concentrations (higher than 15 μg/ml) significantly more frequently at initial measurement (0% vs 80%, p<0.01) and at 7-10 days (0% vs 90%, p=0.045) and achieved PD targets more frequently at increasing MICs. Similarly, compared with every-12-hour dosing, the every-8-hour cefepime dosing strategy significantly increased PD target attainment (fT > MIC ≥ 60%) at an MIC of 8 μg/ml (20% vs 70%, p=0.02).

CONCLUSIONS

This study demonstrated that more frequent dosing of vancomycin and cefepime is required to achieve optimal PD targets in adult neurocritically ill patients. The need for increased total daily doses is potentially secondary to the development of augmented renal clearance.

Comparison of the pharmacokinetics of vancomycin in neurosurgical and non-neurosurgical patients

Although vancomycin concentrations in neurosurgical patients tend to be lower following standard dosing compared with other patient populations, factors influencing vancomycin pharmacokinetics in neurosurgical patients are poorly understood. In this study, pharmacokinetic (PK) parameters in neurosurgical and non-neurosurgical patients were compared. Furthermore, factors influencing vancomycin PK alterations, including those known to augment renal clearance, were determined. Routine therapeutic drug monitoring data from neurosurgical and non-neurosurgical patients were retrospectively collected. Vancomycin PK parameters were estimated using non-linear mixed-effects modelling (NONMEM v.7.2.0); analyses were performed for the entire population and for neurosurgical patients only. Furthermore, the final models performed a bootstrap, visual predictive check and external validation. A total of 359 serum vancomycin concentration data variables from 132 patients were used to execute the PK modelling. Neurosurgical patient factor, the early phase of treatment, underlying liver cirrhosis, co-administration of a nephrotoxic drug and estimated creatinine clearance influenced vancomycin clearance (CL). However, other factors known to augment renal clearance did not affect vancomycin pharmacokinetics. Vancomycin CL was significantly higher in neurosurgical patients than in controls (0.104 ± 0.036 L/h/kg vs. 0.073 ± 0.042 L/h/kg; P <0.01). Augmented vancomycin CL should be considered when determining vancomycin dosages in neurosurgical patients.

Antibacterial therapeutic drug monitoring in cerebrospinal fluid: difficulty in achieving adequate drug concentrations

This report illustrates the difficulty in managing CNS infection in neurosurgical patients, the altered drug pharmacokinetics associated with critical illness, and the role that therapeutic drug monitoring (TDM) of CSF can play in assisting clinical decision making. The authors present a case of external ventricular drain-related ventriculitis in a critically ill patient who initially presented with a subarachnoid hemorrhage. They discuss the physiological changes found in such patients, in particular augmented renal clearance (demonstrated in this patient by a measured creatinine clearance of 375 ml/min/1.73 m(2)), noting the effect this had on drug pharmacokinetics and leading to dosing requirements 2-3 times those recommended in standard regimens. The authors consider the bacterial "kill" characteristics of 2 different antibacterial agents (meropenem and vancomycin) and describe the unique approach of using plasma and CSF TDM to achieve optimal drug exposure at the site of infection while limiting toxic side effects. The authors demonstrate that simply using plasma TDM as a surrogate marker for drug concentration in the CNS may lead to underdosing, exemplified in this patient by CSF vancomycin concentrations as little as 13% of that in plasma. Finally, by measuring CSF and plasma ratios, the authors illustrate the disparity in pharmacokinetic properties between drugs, reminding the clinician of the importance of CNS penetration when selecting antibacterial agents in such cases. This work raises an important hypothesis in the accurate prescription of antibacterial agents in neurosurgical critical care, namely underdosing in the context of augmented elimination and impaired target site penetration. However, prior to any recommendations regarding empirical dose modification, more data are clearly needed, particularly with respect to the safety and efficacy of such an approach. In this respect, the authors would advocate further research using TDM in the management of CNS infection in this setting, in addition to work defining plasma and CSF concentrations associated with antibacterial efficacy and toxicity.