Population Pharmacokinetics of Combined Intravenous and Local Intrathecal Administration of Meropenem in Aneurysm Patients with Suspected Intracranial Infections After Craniotomy

Case report: Analysis of the efficacy and safety of anti-infectious treatment for brain abscess caused by oral anaerobes

Anaerobic meningitis is relatively rare, and the positivity rate of cerebrospinal fluid (CSF) cultures is exceedingly low, particularly in light of the limited research data regarding bacterial meningitis caused by oral anaerobes. This report presents a case involving a 24-year-old woman who developed fever and headache 32 days after undergoing a cesarean section. The symptoms persisted for 2 weeks, and enhanced nuclear magnetic resonance (NMR) scanning confirmed the suspicion of a brain abscess. Additionally, metagenomic next-generation sequencing (mNGS) of cerebrospinal fluid (CSF) identified several microbial species, including Porphyromonas gingivalis, Prevotella heparinolyticus, Fusobacterium nucleatum, Parvimonas micra and Filifactor alocis. Bacterial culture of CSF revealed the growth of Prevotella heparinolyticus. Following bilateral ventricular external drainage, intracranial lesion resection, and the implantation of an Ommaya reservoir in the right lateral ventricle, cranial decompression treatment was performed. Antimicrobial therapy administered successively over a period of 6 weeks, including vancomycin, meropenem, metronidazole, polymyxin B and ceftazidime, resulting in significant control of the infection. Clinical pharmacists engaged in comprehensive discussions with clinicians regarding the antimicrobial drug regimens and recommended a combined regimen of meropenem and metronidazole. An individualized anti-infective treatment protocol was developed based on therapeutic drug monitoring (TDM), which is anticipated to yield valuable insights for the management of brain abscesses resulting from oral anaerobic bacteria.

Population pharmacokinetics of levetiracetam in Chinese adult epilepsy patients with varying renal function: exposure simulation and individualized dosing adjustments

Levetiracetam (LEV) has become a first-line treatment option for various types of epilepsy with a broad spectrum of efficacy and favorable pharmacokinetic profile. We aimed to develop a population pharmacokinetic (PPK) model for LEV and devise a model-based dosing guideline specific to Chinese adult epilepsy patients. Employing Phoenix NLME 7.0 software, we utilized the first-order conditional estimation and extended least squares method to establish the PPK model. The PK of LEV was effectively characterized using a one-compartment model. Monte Carlo simulations were then performed to generate dosing guidelines suitable for various patient groups. The Bayesian feedback method was employed to develop the clinical individual predictive model. Data from 80 Chinese adult patients yielded 148 LEV plasma concentrations for analysis. In the final model, the absorption rate constant was fixed at 2.44. The apparent volume of distribution and the apparent clearance (CL/F) had population typical values of 35.34 L and 3.24 L/h, respectively. CL/F of LEV was significantly influenced by creatinine clearance (CrCL), identified as a major covariate. Monte Carlo simulations indicated that regimens of 0.5 g, 0.75 g, 1.0 g, 1.5 g, 2.0 g, 2.5 g, and 3.5 g twice daily were associated with the highest probability of target attainment (PTA) in patients with different renal function levels. Accordingly, a user-friendly dose recommendation was formulated for these patients. The individual predictive model accurately matched the observed concentrations and managed to guide the personalized dose adjustment. The PPK model linked CL/F to CrCL. Model-based simulations suggest that higher dosage adjustments may be necessary for those with augmented renal function. The developed clinical individual predictive model could effectively guide personalized dose adjustments, potentially reducing the need for frequent drug concentration measurements.

Meropenem pharmacokinetics in cerebrospinal fluid: comparing intermittent and continuous infusion strategies in critically ill patients-a prospective cohort study

Meropenem penetration into the cerebrospinal fluid (CSF) is subject to high interindividual variability resulting in uncertain target attainment in CSF. Recently, several authors recommended administering meropenem as a continuous infusion (CI) to optimize CSF exposure. This study aimed to compare the concentrations and pharmacokinetics of meropenem in CSF after intermittent infusion (II) and CI. This prospective, observational study (NCT04426383) included critically ill patients with external ventricular drains who received either II or CI of meropenem. Meropenem pharmacokinetics in plasma and CSF were characterized using population pharmacokinetic modeling (NONMEM 7.5). The developed model was used to compare the concentration-time profile and probability of target attainment (PTA) between II and CI. A total of 16 patients (8 CI, 8 II; samples: nplasma = 243, nCSF = 263) were recruited, with nine patients (5 CI, 4 II) suffering from cerebral and seven patients from extracerebral infections. A one-compartment model described the plasma concentrations adequately. Meropenem penetration into the CSF (partition coefficient (KP), cCSF/cplasma) was generally low (6.0%), exhibiting substantial between-subject variability (coefficient of variation: 84.0%). There was no correlation between the infusion mode and KP, but interleukin (IL)-6 measured in CSF showed a strong positive correlation with KP (P < 0.001). Dosing simulations revealed no relevant differences in CSF concentrations and PTA in CSF between CI and II. Our study did not demonstrate increased penetration rates or higher concentrations of meropenem in the CSF with CI compared with II.

CLINICAL TRIALS

This study is registered with ClinicalTrials.gov as NCT04426383.

Comprehensive Therapeutic Approaches to Tuberculous Meningitis: Pharmacokinetics, Combined Dosing, and Advanced Intrathecal Therapies

Tuberculous meningitis (TBM) presents a critical neurologic emergency characterized by high mortality and morbidity rates, necessitating immediate therapeutic intervention, often ahead of definitive microbiological and molecular diagnoses. The primary hurdle in effective TBM treatment is the blood-brain barrier (BBB), which significantly restricts the delivery of anti-tuberculous medications to the central nervous system (CNS), leading to subtherapeutic drug levels and poor treatment outcomes. The standard regimen for initial TBM treatment frequently falls short, followed by adverse side effects, vasculitis, and hydrocephalus, driving the condition toward a refractory state. To overcome this obstacle, intrathecal (IT) sustained release of anti-TB medication emerges as a promising approach. This method enables a steady, uninterrupted, and prolonged release of medication directly into the cerebrospinal fluid (CSF), thus preventing systemic side effects by limiting drug exposure to the rest of the body. Our review diligently investigates the existing literature and treatment methodologies, aiming to highlight their shortcomings. As part of our enhanced strategy for sustained IT anti-TB delivery, we particularly seek to explore the utilization of nanoparticle-infused hydrogels containing isoniazid (INH) and rifampicin (RIF), alongside osmotic pump usage, as innovative treatments for TBM. This comprehensive review delineates an optimized framework for the management of TBM, including an integrated approach that combines pharmacokinetic insights, concomitant drug administration strategies, and the latest advancements in IT and intraventricular (IVT) therapy for CNS infections. By proposing a multifaceted treatment strategy, this analysis aims to enhance the clinical outcomes for TBM patients, highlighting the critical role of targeted drug delivery in overcoming the formidable challenges presented by the blood-brain barrier and the complex pathophysiology of TBM.

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 (>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.

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.

Risk factors of intracranial infection in patients after intracranial aneurysm surgery: Implication for treatment strategies

Postoperative intracranial infection after intracranial aneurysm is relatively common in clinical setting; it is necessary to analyze the clinical risk factors of postoperative intracranial infection, to provide reliable evidence to the management of aneurysm.Patients with intracranial aneurysm admitted from January 1, 2016, to November 30, 2020, are included. We collected the patient's personal and treatment data, and analyzed the risk factors of intracranial infection by multivariate logistic regression analysis. We compared the cerebrospinal fluid (CSF) indicators and serological indicators and analyzed their correlation with intracranial infection by spearman analysis.A total of 236 patients with intracranial aneurysm were included; the incidence of postoperative intracranial infection was 12.71%. There were significant differences in the diabetes, intraoperative aneurysm rupture, intraoperative CSF leakage, duration of surgery, and estimated blood loss between infection and non-infection group. Logistic regression indicated that diabetes [odds ratio (OR) 2.053, 95% confidence interval (95% CI) 1.092∼3.385], intraoperative aneurysm rupture (OR 2.239, 95% CI 1.173∼4.312), intraoperative CSF leakage (OR 2.168, 95% CI 1.033∼3.451), duration of surgery ≥360 minutes (OR 1.926, 95% CI 1.108∼2.655), and estimated blood loss ≥125 mL (OR 2.459, 95% CI 1.854∼3.447) were the independent risk factors of postoperative intracranial infection in patients with aneurysm surgery (all P < .05). Klebsiella pneumoniae, Escherichia coli, and Staphylococcus epidermidis were the top 3 commonly seen pathogens. Spearman analyses indicated that PCT, CRP, LA, LDH were all correlated with intracranial infection (all P < .05).There are multiple factors for the postoperative intracranial infection in patients with aneurysm. Coping strategies should be formulated targeted on those risks to improve the prognosis of patients.

Carbenoxolone has the potential to ameliorate acute incision pain in rats

Carbenoxolone (CBX) is primarily used to relieve various types of neuropathic and inflammatory pain. However, little is known concerning the role of CBX in acute pain and its functional mechanisms therein and this was investigated in the present study. Rats underwent toe incision and behavioral tests were performed to assess mechanical hypersensitivity. The expression levels of pannexin 1 (Px1) and connexin 43 (Cx43) were detected using western blot analysis 2, 4, 6 or 24 h after toe incision, and the expression of TNF-α, IL-1β and P substance (SP) was determined by ELISA; Px1 and Cx43 expression was also examined by immunofluorescence staining. At 2, 6 and 12 h post-toe incision, the postoperative pain threshold was significantly reduced, which was subsequently recovered at 2 and 6 h post-surgery following pretreatment with CBX or pannexin 1 mimetic inhibitory peptide. CBX reduced Px1 levels at 4 and 24 h post-incision. However, Cx43 levels were reduced by CBX as little as 2 h post-surgery. Furthermore, CBX not only distinctly decreased the levels of Px1 and Cx43, but also reduced the co-localization of Px1 or Cx43 with glial fibrillary acidic protein, 2 h after incision. It was also observed that the protein levels of inflammatory makers (IL-1β, SP and TNF-α) showed a tendency to decline at 2, 4, 6 and 24 h after incision. Collectively, the expression of Px1 and Cx43 in astrocytes may be involved in pain behaviors diminished by CBX, and CBX potentially reduces acute pain by decreasing Px1 and Cx43 levels. Px1 and Cx43 from spinal astrocytes may serve important roles in the early stages and maintenance of acute pain, while preoperative injection of CBX has the potential to relieve hyperalgesia.

Impact of gender, albumin, and CYP2C19 polymorphisms on valproic acid in Chinese patients: a population pharmacokinetic model

OBJECTIVE

This prospective study aimed to establish the valproic acid (VPA) population pharmacokinetic model in Chinese patients and realise personalised medication on the basis of population pharmacokinetics.

METHODS

The patients' clinical information and VPA plasma concentrations were collected from The General Hospital of Taiyuan Iron & Steel (Group) Corporation (TISCO). Nonlinear mixed-effect modelling was used to build the population pharmacokinetic model. To characterise the pharmacokinetic data, a one-compartment pharmacokinetic model with first-order absorption and elimination was used. The first-order conditional estimation with η-ε interaction was applied throughout the model-developing procedure. The absorption rate constant (Ka) was fixed at 2.38 hour^-1, and the impact of covariates on clearance and apparent volume of distribution were also explored. Medical records of 60 inpatients were reviewed prospectively and the objective function value (OFV) of the base model and final model were 851.813 and 817.622, respectively.

RESULTS

Gender was identified as the covariate that had a significant impact on the volume of distribution, and albumin and CYP2C19 genotypes influenced clearance.

CONCLUSION

Bootstrap and VPC indicated that a reliable model had been developed that was based on the simulation results, and a simple-to-use dosage regimen table was created to guide clinicians for VPA drug dosing.

Population pharmacokinetics of high-dose methotrexate in Chinese pediatric patients with medulloblastoma

Methotrexate (MTX) pharmacokinetics has substantial inter-individual variability and toxicity. In children with medulloblastoma treated with high-dose methotrexate (HD-MTX), the pharmacokinetic properties of methotrexate have not been established. A total of 660 serum samples from 105 pediatric patients with medulloblastoma were included in a population pharmacokinetic (PPK) analysis of methotrexate by using the nonlinear mixed-effects modeling method. The basic one-compartment population pharmacokinetic model was established by NONMEM software and the first-order conditional estimation (FOCE) method, and the final covariate model was obtained by the stepwise regression method. Weight (WT), creatinine clearance (CrCL), and whether the treatment was combined with dexamethasone (DEX) were covariates that had significant effects on the clearance rate (CL) of the model. The pharmacokinetic equation of CL in the final covariate model was as follows: CL_i = 9.23× (1 + 0.0005× (θ_CrCL -105.78)) × (1 + 0.0017× (θ_WT -16)) × e^ηcl,i (L/h), IF (θ_DEX ) CL_i = 1.19× CL_i (L/h). The estimation accuracy of all pharmacokinetic parameters were acceptable (relative standard error < 14.74%). The goodness-of-fit diagram and bootstrap tests indicated that the final PPK model was stable with acceptable predictive ability. The PPK model may be useful for determining personalized medication levels in pediatric medulloblastoma patients undergoing HD-MTX therapy.

Pharmacokinetic interaction between shuanghuanglian and azithromycin injection: a nonlinear mixed-effects model analysis in rats

1. This study aimed to evaluate the pharmacokinetic interaction of shuanghuanglian (SHL) and azithromycin in rats, and to provide experimental support for rational drug use in clinics. 2. High-performance liquid chromatography with ultraviolet detection (HPLC-UV) and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) approaches were respectively developed to detect the forsythiaside (active component of SHL) and azithromycin concentrations. Both non-compartmental and compartmental analyzes were employed to calculate pharmacokinetic parameters. A nonlinear mixed-effects modeling method was applied to fit the drug concentration-time data. The influence of drug coadministration on pharmacokinetic parameters was tested using forward inclusion and backward elimination procedures. 3. After drug co-administration, areas under the drug concentration-time curve (AUC) and half-lives (T_1/2) of both azithromycin and forsythiaside increased significantly, meanwhile, the drug clearance (CL) decreased compared to single drug administration. Both forsythiaside and azithromycin exposures increased after coadministration. Two-compartment models were suitable to describe the in vivo behavior of both azithromycin and forsythiaside. The coadministration of SHL could significantly decrease the central volume of azithromycin (V_CA) and forsythiaside clearance (CL_F) decreased after co-intravenous administration of azithromycin. 4. Co-intravenous administration of forsythiaside and azithromycin could significantly increase drug exposures for both drugs. Lower dose can provide sufficient drug exposure to obtain antibacterial activity. The coadministration may be a potential method to increase therapy efficiency while decrease adverse drug reactions.

Scaling beta-lactam antimicrobial pharmacokinetics from early life to old age

AIMS

Beta-lactam dose optimization in critical care is a current priority. We aimed to review the pharmacokinetics (PK) of three commonly used beta-lactams (amoxicillin ± clavulanate, piperacillin-tazobactam and meropenem) to compare PK parameters reported in critically and noncritically ill neonates, children and adults, and to investigate whether allometric and maturation scaling principles could be applied to describe changes in PK parameters through life.

METHODS

A systematic review of PK studies of the three drugs was undertaken using MEDLINE and EMBASE. PK parameters and summary statistics were extracted and scaled using allometric principles to 70 kg individual for comparison. Pooled data were used to model clearance maturation and decline using a sigmoidal (Hill) function.

RESULTS

A total of 130 papers were identified. Age ranged from 29 weeks to 82 years and weight from 0.9-200 kg. PK parameters from critically ill populations were reported with wider confidence intervals than those in healthy volunteers, indicating greater PK variability in critical illness. The standard allometric size and sigmoidal maturation model adequately described increasing clearance in neonates, and a sigmoidal model was also used to describe decline in older age. Adult weight-adjusted clearance was achieved at approximately 2 years postmenstrual age. Changes in volume of distribution were well described by the standard allometric model, although amoxicillin data suggested a relatively higher volume of distribution in neonates.

CONCLUSIONS

Critical illness is associated with greater PK variability than in healthy volunteers. The maturation models presented will be useful for optimizing beta-lactam dosing, although a prospective, age-inclusive study is warranted for external validation.

Plasma and cerebrospinal fluid population pharmacokinetic modeling and simulation of meropenem after intravenous and intrathecal administration in postoperative neurosurgical patients

Combined intravenous and local intrathecal administration of meropenem in patients after craniotomy is widely used to treat intracranial infections. However, the optimal dosing regimen of meropenem has not been investigated, posing a risk to treatment efficacy. We aimed to identify significant factors associated with inter-individual variability in cerebrospinal fluid (CSF) pharmacokinetics of meropenem and to evaluate potential intravenous and intrathecal meropenem dosing regimens for the treatment of patients with intracranial infections. After the diagnosis of intracranial infection, 15 patients with an indwelling drain tube received intravenous and intrathecal administration of meropenem. Blood and cerebrospinal fluid (CSF) samples were obtained at the scheduled time to measure meropenem concentration. Plasma and CSF concentration-time data were fit simultaneously using a nonlinear mixed-effects modeling approach. A 3-compartmental model was selected to characterize the in vivo behavior of meropenem. Through population modeling, multiple covariates were tested about their impact on the meropenem pharmacokinetics. Considering CSF outflow via drain tube leading to a drug loss, the drug clearance in CSF (CL_CSF) was added to describe this drug loss. The covariate selection indicated that the drainage volume (mL/d) had a significant positive correlation with CL_CSF. Bootstrap and visual predictive check suggested a robust and reliable pharmacokinetic model was structured. The established final population model was useful to apply with simulation to identify meropenem dosing regimens for the treatment of patients with intracranial infections. With the goal of CSF concentrations exceeding the minimum inhibitory concentration during the therapy, we created a simple to use dosage regimen table to guide clinicians with drug dosing.