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.

Intraperitoneally Administered Vancomycin in Patients with Peritoneal Dialysis-Associated Peritonitis: Population Pharmacokinetics and Dosing Implications

Peritonitis is a limiting complication of peritoneal dialysis, which is treated by intraperitoneal administration of antibiotics. Various dosing strategies are recommended for intraperitoneally administered vancomycin, which leads to large differences in intraperitoneal vancomycin exposure. Based on data from therapeutic drug monitoring, we developed the first-ever population pharmacokinetic model for intraperitoneally administered vancomycin to evaluate intraperitoneal and plasma exposure after dosing schedules recommended by the International Society for Peritoneal Dialysis. According to our model, currently recommended dosing schedules lead to possible underdosing of a large proportion of patients. To prevent this, we suggest avoiding intermittent intraperitoneal vancomycin administration, and for the continuous dosing regimen, we suggest a loading dose of 20 mg/kg followed by maintenance doses of 50 mg/L in each dwell to improve the intraperitoneal exposure. Vancomycin plasma level measurement on the fifth day of treatment with subsequent dose adjustment would prevent it from reaching toxic levels in the few patients who are susceptible to overdose.

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.

Edaravone attenuates disease severity of experimental auto-immune encephalomyelitis and increases gene expression of Nrf2 and HO-1

The aim of this study was to evaluate therapeutic potential of edaravone in the murine model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE) and to expand the knowledge of its mechanism of action. Edaravone (6 mg/kg/day) was administered intraperitoneally from the onset of clinical symptoms until the end of the experiment (28 days). Disease progression was assessed daily using severity scores. At the peak of the disease, histological analyses, markers of oxidative stress (OS) and parameters of mitochondrial function in the brains and spinal cords (SC) of mice were determined. Gene expression of inducible nitric oxide synthase (iNOS), nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1alpha was determined at the end of the experiment. Edaravone treatment ameliorated EAE severity and attenuated inflammation in the SC of the EAE mice, as verified by histological analysis. Moreover, edaravone treatment decreased OS, increased the gene expression of the Nrf2 and HO-1, increased the activity of the mitochondrial complex II/III, reduced the activity of the mitochondrial complex IV and preserved ATP production in the SC of the EAE mice. In conclusion, findings in this study provide additional evidence of edaravone potential for the treatment of multiple sclerosis and expand our knowledge of the mechanism of action of edaravone in the EAE model.

Molecular biomarkers in multiple sclerosis

Multiple sclerosis (MS) is a highly heterogenous disease regarding radiological, pathological, and clinical characteristics and therapeutic response, including both the efficacy and safety profile of treatments. Accordingly, there is a high demand for biomarkers that sensitively and specifically apprehend the distinctive aspects of the MS heterogeneity, and that can aid in better understanding of the disease diagnosis, prognosis, prediction of the treatment response, and, finally, in the development of new treatments. Currently, clinical characteristics (e.g., relapse rate and disease progression) and magnetic resonance imaging play the most important role in the clinical classification of MS and assessment of its course. Molecular biomarkers (e.g., immunoglobulin G (IgG) oligoclonal bands, IgG index, anti-aquaporin-4 antibodies, neutralizing antibodies against interferon-beta and natalizumab, anti-varicella zoster virus and anti-John Cunningham (JC) virus antibodies) complement these markers excellently. This review provides an overview of exploratory, validated and clinically useful molecular biomarkers in MS which are used for prediction, diagnosis, disease activity and treatment response.

Population pharmacokinetics-pharmacodynamics of fondaparinux in dialysis-dependent chronic kidney disease patients undergoing chronic renal replacement therapy

PURPOSE

Data on the anti-Xa efficacy of fondaparinux in dialysis-dependent chronic kidney disease (DD-CKD) patients are scarce. This study characterizes the pharmacokinetics (PK) and pharmacodynamics (PD) of fondaparinux in DD-CKD patients undergoing renal replacement therapy (RRT), to assess dosing strategies.

METHODS

A retrospective, observational study was conducted using data on anti-Xa activity (112 samples) from 12 (3 male and 9 female) DD-CKD patients (median (IQR) age 71 years (63-88), weight 73 kg (59-98.5)). Eleven patients underwent high-flux or low-flux hemodialysis (HD) and one patient underwent peritoneal dialysis. Three patients were also treated with therapeutic plasma exchange (TPE). A non-linear mixed effects analysis was performed using NONMEM 7.3.0.

RESULTS

The lab-specific slope of the relationship between fondaparinux concentration and anti-Xa levels was 1.18 IU/µg. In a one-compartment model, clearance (CL) and volume of distribution (Vd) were 0.05289 L/h and 5.55 L, respectively. High-flux HD was found to increase the CL of fondaparinux 2.26 times. TPE also considerably increased CL, but the fold-change could not be accurately estimated. Low-flux HD and peritoneal dialysis did not impact PK parameters.

CONCLUSIONS

Model-based simulations showed that standard dosing (2.5 mg three times weekly before HD) results in a median anti-Xa activity of 0.55 IU/mL and 0.98 IU/mL, pre- and post-low-flux HD, respectively. In patients undergoing high-flux HD, these values are approximately 27% lower. Additional caution is warranted with TPE, as this treatment can reduce anti-Xa activity even further.

No Time Dependence of Ciprofloxacin Pharmacokinetics in Critically Ill Adults: Comparison of Individual and Population Analyses

The aim of this prospective PK study was to evaluate the pharmacokinetics of ciprofloxacin dosed within the first 36 h (early phase) and after 3 days of treatment (delayed phase) using individual and population PK analysis. The secondary aim of the study was to evaluate possible dosing implications of the observed PK differences between early and delayed phases to achieve a PK/PD target for ciprofloxacin of AUC₂₄/MIC ≥ 125. Blood concentrations of ciprofloxacin (1 and 4 h after dose and trough) were monitored in critically ill adults in the early and delayed phases of the treatment. Individual and population PK analyses were performed. Complete concentration-time profiles in the early phase, delayed phase, and both phases were obtained from 29, 15, and 14 patients, respectively. No systematic changes in ciprofloxacin PK parameters between the early and delayed phases were observed, although variability was higher at the early phase. Both individual and population analyses provided similar results. Simulations showed that after standard dosing, it is practically impossible to reach the recommended ciprofloxacin PK/PD target (AUC/MIC ≥ 125) for pathogens with MIC ≥ 0.5 mg/L. A dosing nomogram utilizing patients’ creatinine clearance and MIC values was constructed. Both individual and population analyses provided similar results. Therapeutic drug monitoring should be implemented to safeguard the optimal ciprofloxacin exposure.

Novel approaches in schizophrenia-from risk factors and hypotheses to novel drug targets

Schizophrenia is a severe psychiatric disorder characterized by emotional, behavioral and cognitive disturbances, and the treatment of schizophrenia is often complicated by noncompliance and pharmacoresistance. The search for the pathophysiological mechanisms underlying schizophrenia has resulted in the proposal of several hypotheses to explain the impacts of environmental, genetic, neurodevelopmental, immune and inflammatory factors on disease onset and progression. This review discusses the newest insights into the pathophysiology of and risk factors for schizophrenia and notes novel approaches in antipsychotic treatment and potential diagnostic and theranostic biomarkers. The current hypotheses focusing on neuromediators (dopamine, glutamate, and serotonin), neuroinflammation, the cannabinoid hypothesis, the gut-brain axis model, and oxidative stress are summarized. Key genetic features, including small nucleotide polymorphisms, copy number variations, microdeletions, mutations and epigenetic changes, are highlighted. Current pharmacotherapy of schizophrenia relies mostly on dopaminergic and serotonergic antagonists/partial agonists, but new findings in the pathophysiology of schizophrenia have allowed the expansion of novel approaches in pharmacotherapy and the establishment of more reliable biomarkers. Substances with promising results in preclinical and clinical studies include lumateperone, pimavanserin, xanomeline, roluperidone, agonists of trace amine-associated receptor 1, inhibitors of glycine transporters, AMPA allosteric modulators, mGLUR_2-3 agonists, D-amino acid oxidase inhibitors and cannabidiol. The use of anti-inflammatory agents as an add-on therapy is mentioned.

Post-mortem Redistribution of Alprazolam in Rats

The post-mortem toxicological findings may be misinterpreted, if the drug undergoes substantial post-mortem redistribution. As alprazolam is one of the most frequently evaluated drug for legal/forensic reasons in drug-related fatalities, we studied possible changes in alprazolam distribution after death in a rat model. Rats were sacrificed 30 minutes after alprazolam administration. Blood and tissue samples from 8 animals per sampling time were collected at 0, 2, 6, and 24 h after death. The experimental samples were assayed for alprazolam using validated UHPLC-PDA method. Median blood alprazolam concentrations increased approximately 2 times compared with ante-mortem levels due to the redistribution during early post-mortem phase and then slowly decreased with a half-life of 60.7 h. The highest alprazolam tissue concentrations were found in fat and liver and the lowest levels were observed in lungs and brain. The median amount of alprazolam deposited in the lungs was relatively stable over the 24-h post-mortem period, while in heart, liver and kidney the deposited proportion of administered dose increased by 43-48% in comparison with ante-mortem values indicating continuous accumulation of alprazolam into these tissues. These results provide evidence needed for the interpretation of toxicological results in alprazolam-related fatalities and demonstrate modest alprazolam post-mortem redistribution.

Severity parameters for asphyxia or hypoxic-ischemic encephalopathy do not explain inter-individual variability in the pharmacokinetics of phenobarbital in newborns treated with therapeutic hypothermia

BACKGROUND

The current study uses a population modeling approach to evaluate and quantify the impact of severity of asphyxia and hypoxic-ischemic encephalopathy (HIE) on the pharmacokinetics of phenobarbital in asphyxiated newborns treated with therapeutic hypothermia.

METHODS

Included newborns received phenobarbital (the TOBY trial protocol). 120 plasma samples were available from 50 newborns, median (IQR) weight 3.3 (2.8-3.5) kg and gestational age 39 (39-40) weeks. NONMEM^® version 7.2 was used for the data analysis. Age, body weight, sex, concomitant medications, kidney and liver function markers, as well as severity parameters of asphyxia and HIE were tested as potential covariates of pharmacokinetics of phenobarbital. Severe asphyxia was defined as pH of arterial umbilical cord blood ≤7.1 and Apgar 5 ≤5, and severe HIE was defined as time to normalization of amplitude-integrated electroencephalography (aEEG) >24 h.

RESULTS

Weight was found to be the only statistically significant covariate for the volume of distribution. At weight of 1 kg volume of distribution was 0.91 L and for every additional kg it increased in 0.91 L. Clearance was 0.00563 L/h. No covariates were statistically significant for the clearance of phenobarbital.

CONCLUSIONS

Phenobarbital dose adjustments are not indicated in the studied population, irrespective of the severity of asphyxia or HIE.

Severity parameters for asphyxia or hypoxic-ischemic encephalopathy do not explain interindividual variability in the pharmacokinetics of phenobarbital in newborns treated with therapeutic hypothermia

BACKGROUND

The current study uses a population modeling approach to evaluate and quantify the impact of severity of asphyxia and hypoxic-ischemic encephalopathy (HIE) on the pharmacokinetics of phenobarbital in asphyxiated newborns treated with therapeutic hypothermia.

METHODS

Included newborns received phenobarbital (the TOBY trial protocol). 120 plasma sample were available from 50 newborns, median (IQR) weight 3.3 (2.8-3.5) kg and gestational age 39 (39-40) weeks. NONMEM version 7.2® was used for the data analysis. Age, body weight, sex, concomitant medications, kidney and liver function markers, as well as severity parameters of asphyxia and HIE were tested as potential covariates of pharmacokinetics of phenobarbital. Severe asphyxia was defined as pH of arterial umbilical cord blood ≤7.1 and Apgar 5 ≤5, and severe HIE was defined as time to normalization of amplitude-integrated electroencephalography (aEEG) >24 h.

RESULTS

Weight was found to be the only statistically significant covariate for the volume of distribution. At weight of 1 kg volume of distribution was 0.91 L and for every additional kg it increased in 0.91 L. Clearance was 0.00563 L/h. No covariates were statistically significant for the clearance of phenobarbital.

CONCLUSIONS

Phenobarbital dose adjustments are not indicated in the studied population, irrespective of the severity of asphyxia or HIE.

Population pharmacokinetics of riociguat and its metabolite in patients with chronic thromboembolic pulmonary hypertension from routine clinical practice

Pharmacokinetic data for riociguat in patients with chronic thromboembolic pulmonary hypertension (CTEPH) have previously been reported from randomized clinical trials, which may not fully reflect the population encountered in routine practice. The aim of the current study was to characterize the pharmacokinetic of riociguat and its metabolite M1 in the patients from routine clinical practice. A population pharmacokinetic model was developed in NONMEM 7.3, based on riociguat and its metabolite plasma concentrations from 49 patients with CTEPH. One sample with riociguat and M1 concentrations was available from each patient obtained at different time points after last dose. Age, bodyweight, sex, smoking status, concomitant medications, kidney and liver function markers were tested as potential covariates of pharmacokinetic of riociguat and its metabolite. Riociguat and M1 disposition was best described with one-compartment models. Apparent volume of distribution (Vd/F) for riociguat and M1 were assumed to be the same. Total bilirubin and creatinine clearance were the most predictive covariates for apparent riociguat metabolic clearance to M1 (CL_f,M1/F) and for apparent riociguat clearance through remaining pathways (CL_e,r/F), respectively. CL_f,M1/F, CL_e,r/F, Vd/F of riociguat and M1, and clearance of M1 (CL_e,M1/F) for a typical individual with 70 mL/min creatinine clearance and 0.69 mg/dL total bilirubin were 0.665 L/h (relative standard error = 17%)), 0.66 (18%) L/h, 3.63 (15%) L and 1.47 (19%) L/h, respectively. Upon visual identification of six outlying individuals, an absorption lag-time of 2.95 (6%) h was estimated for these patients. In conclusion, the only clinical characteristics related to riociguat exposure in patients with CTEPH from routine clinical practice are total bilirubin and creatinine clearance. This confirms the findings of the previous population pharmacokinetic studies based on data from randomized clinical trials.

New insights in the mechanisms of impaired redox signaling and its interplay with inflammation and immunity in multiple sclerosis

Multiple sclerosis (MS) is an autoimmune neurological disease characterized by chronic inflammation of the central nervous system (CNS), leading to demyelination and axonal damage and resulting in a range of physical, mental or even psychiatric symptoms. Key role of oxidative stress (OS) in the pathogenesis of MS has been suggested, as indicated by the biochemical analysis of cerebrospinal fluid and blood samples, tissue homogenates, and animal models of multiple sclerosis. OS causes demyelination and neurodegeneration directly, by oxidation of lipids, proteins and DNA but also indirectly, by inducing a dysregulation of the immunity and favoring the state of pro-inflammatory response. In this review, we discuss the interrelated mechanisms of the impaired redox signaling, of which the most important are inflammation-induced production of free radicals by activated immune cells and growth factors, release of iron from myelin sheath during demyelination and mitochondrial dysfunction and consequent energy failure and impaired oxidative phosphorylation. Review also provides an overview of the interplay between inflammation, immunity and OS in MS. Finally, this review also points out new potential targets in MS regarding attenuation of OS and inflammatory response in MS.

Comparison of Polyphenol-Enriched Tomato Juice and Standard Tomato Juice for Cardiovascular Benefits in Subjects with Stage 1 Hypertension: a Randomized Controlled Study

There is a growing body of evidence that tomato consumption reduces the risk of cardiovascular disease, through antioxidative, anti-inflammatory and hypotensive effects. We compared the effects of polyphenol-enriched and standard tomato juice on parameters of lipid and oxidative status and blood pressure in subjects with stage 1 hypertension. The experimental group (n = 13) was supplemented with 200 g of tomato fruit juice enriched with 1 g of ethanolic extract of whole tomato fruit, while the control group (n = 13) was consuming 200 g tomato fruit juice. Before and after the treatment, blood samples were collected, and blood pressure was measured. Markers of oxidative stress and antioxidative defense: paraoxonase (PON1), thiobarbituric acid reactive substances (TBARS), total antioxidant status (TAS), total oxidant status (TOS), pro-oxidant-antioxidant balance (PAB) and C reactive protein (CRP) were determined in serum. Prothrombin time (PT) was measured in the whole blood samples. Parameters of lipid status, as well as susceptibility to copper-induced oxidation of LDL particles in vitro were also determined. There was a significant reduction in total cholesterol and LDL-C only in the control group at the end of the study. No significant differences were observed in the remainder of the assessed parameters along the study. In conclusion, tomato juice may have favorable effects on lipid metabolism, but polyphenol fortification does not constitute additional beneficial cardiovascular effects.