Pharmacokinetic Parameter Values Research Articles

612. Pharmacokinetics of Piperacillin-Tazobactam in Patients with Severe Infections

Abstract Background Piperacillin-Tazobactam (PIP/TAZ) is a combination of a β-lactam antibiotic with a β-lactamase inhibitor, used to treat moderate to severe infections due to its broad-spectrum antibacterial activity. Its bactericidal effect is time-dependent. Therefore, the free-drug concentration should remain above the minimum inhibitory concentration during at least 50% of the dosing interval. Patients with severe infections develop pathophysiological changes that alter drugs pharmacokinetics (PK), leading to only 30% of probability of target attainment in clinical setting. Methods A prospective observational study was performed in patients with severe infections from Hospital Central “Dr. Ignacio Morones Prieto”. The protocol was approved by the Research and Ethics Committee (register 05-20) and patients signed written informed consent. Samples were collected at steady-state and plasma concentrations were quantified by liquid chromatography coupled to mass spectrometry. Data were analyzed by a population approach using NONMEM® software. Results A total of 52 patients were included (52% male) with a mean age of 46 ± 17 years and a body mass index of 25 ± 5 Kg/m2. According to the Akaike information criterion and visual inspection, a one-compartment open model was chosen to describe the concentration vs time data (n=156) for both drugs. Typical values (relative standard error) of PK parameters obtained were Clearance [CLPIP (L/h)] = 8.79 (12%) and Volume of distribution [VPIP (L)] = 17.6 (13%); and CLTAZ (L/h) = 12.6 (14%), VTAZ (L) = 32.8 (13%). Interindividual variability (IIV) of each parameter was modeled by exponential error and reported as coefficient of variation as follows: 75.3% and 88.7% for CL; 67.2% and 68.8% for V of PIP and TAZ, respectively. Finally, residual error was modeled as additive and presented a standard deviation (SD) of 7.28 µg/mL for PIP, and for TAZ was modeled as a combined with a SD of 0.22 µg/mL and a coefficient of variation of 17.32%. Conclusion Individualization and optimization of β-lactam dosing are essential in drugs with wide IIV as PIP/TAZ; hence, development of a population PK model will provide a valuable aid in explaining and quantifying some of this variability to allow a priori predictions to design initial regimens to reach pharmacotherapeutic targets. Disclosures All Authors: No reported disclosures.

Lidocaine clearance as pharmacokinetic parameter of metabolic hepatic activity in patients with impaired liver.

The study aimed to estimate lidocaine (LID) pharmacokinetic parameter values in patients with impaired liver function, level of correlation between the pharmacokinetic parameters and Child-Pugh class and change in pharmacokinetic parameters after liver tumor resection compared to the preoperative value. Patients with impaired liver function were subject to the LID test 1 day prior to, 3 and 7 days after the intervention. LID was administered in single i.v. dose of 1 mg/kg. Blood samples were collected at 15, 30 and 90 minutes after drug administration. Non-compartmental analysis was applied for calculating the pharmacokinetic parameters. The study included 17 patients with the diagnosis of cirrhosis and 41 patients with liver tumor. In both groups of patients, the values of the coefficients of correlation show the best correlation between clearance (CL) and Child-Pugh score (-0.693, p<0.005) over other pharmacokinetic parameters. The results indicate worsening hepatic function on 3rd day after operation in comparison to the values of LID CL prior to operation (mean LID CL for patients with Child-Pugh class A are 25.91 L/h, 41.59 L/h, respectively; while for B class are 16.89 L/h, 22.65 L/h, respectively). On day 7th, the values of LID CL (mean value for patients with Child-Pugh class A and B are 40.98 L/h and 21.46 L/h, respectively) are increased in comparison to 3rd day after. LID pharmacokinetic parameters consequently changed according to the severity of liver impairment, assessed by Child-Pugh score. Values of LID CL and volume of distribution (Vd) coupled with standard biochemical parameters may be used for preoperative assessment of liver function and monitoring of its postoperative recovery.

Feasibility of a Pragmatic PBPK Modeling Approach: Towards Model-Informed Dosing in Pediatric Clinical Care.

More than half of all drugs are still prescribed off-label to children. Pharmacokinetic (PK) data are needed to support off-label dosing, however for many drugs such data are either sparse or not representative. Physiologically-based pharmacokinetic (PBPK) models are increasingly used to study PK and guide dosing decisions. Building compound models to study PK requires expertise and is time-consuming. Therefore, in this paper, we studied the feasibility of predicting pediatric exposure by pragmatically combining existing compound models, developede.g. for studies in adults, with a pediatric and preterm physiology model. Seven drugs, with various PK characteristics, were selected (meropenem, ceftazidime, azithromycin, propofol, midazolam, lorazepam, and caffeine) as a proof of concept. Simcyp® v20 was used to predict exposure in adults, children, and (pre)term neonates, by combining an existing compound model with relevant virtual physiology models. Predictive performance was evaluated by calculating the ratios of predicted-to-observed PK parameter values (0.5- to 2-fold acceptance range) and by visual predictive checks with prediction error values. Overall, modelpredicted PK in infants, children and adolescents capture clinical data. Confidence in PBPK model performance was therefore considered high. Predictive performance tends to decrease when predicting PK in the (pre)term neonatal population. Pragmatic PBPK modeling in pediatrics, based on compound models verified with adult data, is feasible. A thorough understanding of the model assumptions and limitations is required, before model-informed doses can be recommended for clinical use.

Influence of Different Measurement Methods of Arterial Input Function on Quantitative Dynamic Contrast-Enhanced MRI Parameters in Head and Neck Cancer.

Head and neck cancer (HNC) is the sixth most prevalent cancer worldwide. Dynamic contrast-enhanced MRI (DCE-MRI) helps in diagnosis and prognosis. Quantitative DCE-MRI requires an arterial input function (AIF), which affects the values of pharmacokinetic parameters (PKP). To evaluate influence of four individual AIF measurement methods on quantitative DCE-MRI parameters values (Ktrans , ve , kep , and vp ), for HNC and muscle. Prospective. A total of 34 HNCpatients (23 males, 11 females, age range 24-91) FIELD STRENGTH/SEQUENCE: A 3 T; 3D SPGR gradient echo sequence with partial saturation of inflowing spins. Four AIF methods were applied: automatic AIF (AIFa) with up to 50 voxels selected from the whole FOV, manual AIF (AIFm) with four voxels selected from the internal carotid artery, both conditions without (Mc-) or with (Mc+) motion correction. Comparison endpoints were peak AIF values, PKP values in tumor and muscle, and tumor/muscle PKP ratios. Nonparametric Friedman test for multiple comparisons. Nonparametric Wilcoxon test, without and with Benjamini Hochberg correction, for pairwise comparison of AIF peak values and PKP values for tumor, muscle and tumor/muscle ratio, P value ≤ 0.05 was considered statistically significant. Peak AIF values differed significantly for all AIF methods, with mean AIFmMc+ peaks being up to 66.4% higher than those for AIFaMc+. Almost all PKP values were significantly higher for AIFa in both, tumor and muscle, up to 76% for mean Ktrans values. Motion correction effect was smaller. Considering tumor/muscle parameter ratios, most differences were not significant (0.068 ≤ Wilcoxon P value ≤ 0.8). We observed important differences in PKP values when using either AIFa or AIFm, consequently choice of a standardized AIF method is mandatory for DCE-MRI on HNC. From the study findings, AIFm and inflow compensation are recommended. The use of the tumor/muscle PKP ratio should be of interest for multicenter studies. 2 TECHNICAL EFFICACY: Stage 1.

Pharmacokinetics of hydroxychloroquine in Japanese systemic lupus erythematosus patients with renal impairment.

Reduction of the hydroxychloroquine (HCQ) dosage is recommended in systemic lupus erythematosus (SLE) patients with renal impairment, but a pharmacokinetics (PK) study of patients with renal impairment has not yet been performed. We investigated the PK of both single and multiple doses of HCQ and its metabolites in SLE patients with renal impairment who newly started HCQ at a daily dose of 300 mg based on an ideal body weight dosage of 6.5 mg/kg. Population PK analysis was performed using a non-linear mixed-effects model. In total, 219 samples from 21 patients were analysed. The PK of HCQ in blood after single and multiple oral administrations followed the two-compartment model. At steady state, the concentration ratio of HCQ to each metabolite was HCQ:desethylhydroxychloroquine:desethylchloroquine:bisdesethylchloroquine = 1:0.28:0.1:0.06. The HCQ concentration correlated positively with that of each metabolite. The estimated values (relative standard error) of the population PK parameters were the total clearance at 110 l/h (31%) and a central volume of distribution of 398 l (19%). Co-administration of prednisolone and age, but not renal impairment, were factors affecting the total clearance of HCQ. From the PK perspective, a dosage reduction is unnecessary in SLE patients with impaired renal function.

The Usefulness of In Vitro Percutaneous Absorption Experiments Applying the Infinite Dose Technique to Predict In Vivo Plasma Levels: Comparison of Model-Predicted and Observed Plasma Concentrations of Nortriptyline in Rats.

The aims of this study were to evaluate the feasibility of a nortriptyline (NT) formulation for transdermal administration and to assess the usefulness of an estimated kinetic parameter (kout) using the in vitro infinite dose technique to predict in vivo plasma levels when used in combination with pharmacokinetic parameters. To do so, a simple one-compartment model was used to describe the transport of a permeant across a membrane (skin). This model provides relatively simple expressions for the amount of permeant in the skin, the cumulative amount of permeant that crosses the skin, and the flux of permeant, for both the infinite and the finite dose regimens. Transdermal administration of the formulated NT gel to rats resulted in plasma levels of approximately 150 ng/mL between 8 and 30 h post-administration. These levels were higher than the minimum concentration of 40 ng/mL recommended for smoking cessation therapy and slightly higher than the upper limit of the therapeutic range for the treatment of depression in humans. The one-compartment model used to describe transport across the skin was connected to a two-compartment pharmacokinetic model used to predict NT plasma concentrations in rats using the kout determined in vitro and the values of other pharmacokinetic parameters obtained in vivo. The predicted concentrations were close to the observed plasma levels and the time profiles were similar for both types of data. These results show the usefulness of the kout parameter determined in vitro to predict plasma concentrations of drugs administered percutaneously.

Clinical Application Value of Pharmacokinetic Parameters of Vancomycin in Children Treated in the Pediatric Intensive Care Unit.

ObjectiveTo explore the efficacy and safety of vancomycin as measured by pharmacokinetic/pharmacodynamic parameters in children with severe infection in the Pediatric Intensive Care Unit (PICU) and to determine the appropriate threshold for avoiding nephrotoxicity.MethodsThe medical records of hospitalized children with severe infection treated with vancomycin in the PICU of a tertiary pediatric hospital from September 2018 to January 2021 were retrospectively collected. Univariate analysis was used to assess the correlation between vancomycin pharmacokinetic/pharmacodynamic parameters and therapeutic efficacy or vancomycin-related nephrotoxicity. Binary logistic regression was used to analyze the risk factors for vancomycin-related nephrotoxicity. The vancomycin area under the concentration-time curve over 24 h (AUC0–24) threshold was determined by receiver operating characteristic (ROC) curve analysis.ResultsOne hundred and 10 patients were included in this study. Seventy-six patients (69.1%) exhibited clinically effective response, while the rest exhibited clinically ineffective response. There were no significant differences in APACHE II score, steady-state trough concentration, peak concentration or AUC0–24 of vancomycin between the effective and ineffective groups. Among the 110 patients, vancomycin-related nephrotoxicity occurred in 15 patients (13.6%). Multivariate analysis showed that vancomycin treatment duration, trough concentration, and AUC0–24 were risk factors for vancomycin-related nephrotoxicity. The ROC curve indicated that AUC0–24 < 537.18 mg.h/L was a suitable cutoff point for predicting vancomycin-related nephrotoxicity.ConclusionNo significant correlations were found between the trough concentration or AUC0–24 of vancomycin and therapeutic efficacy when the daily dose of vancomycin was approximately 40 mg/kg d, while the trough concentration and AUC0–24 were both closely related to vancomycin-related nephrotoxicity. The combination of AUC0–24 and trough concentration for therapeutic drug monitoring may reduce the risk of nephrotoxicity.

Passive immunization against COVID-19 by anti-SARS-CoV-2 spike IgG in commercially available immunoglobulin preparations in severe antibody deficiency

Passive immunization against COVID-19 by anti-SARS-CoV-2 spike IgG in commercially available immunoglobulin preparations in severe antibody deficiency

Abstract 6061: Novel β-Apopicropodophyllin derivative, JNC-1043, exerts anti-cancer and radiosensitizing effects

Abstract In this study, we reported novel anti-cancer drug candidate, JNC-1043{(5S)-5-(4-Benzyloxy-3,5-dimethoxy-phenyl)-5,9-dihydro-8H-furo[3',4':6,7] naphtho[2,3-d][1,3]dioxol-6-one}, synthesized from β-Apopicropodophyllin. Firstly, we analyzed anti-cancer effect of JNC-1043. We performed MTT assay to detect IC50 values on several cancer cells - breast, lung, pancreatic, blood, gastric, colorectal cancers. In these experiments, 0.1~1 μM IC50 values of JNC-1043 were calculated, and JNC-1043 treatments induced activation of caspase-3 and -8. Additionally, effective values of pharmacokinetic parameters in male rats and 2 weeks Dose Rate Finding (DRF) of JNC-1043 also detected. This result showed JNC-1043 is a promising anti-cancer candidate. Next, we tested whether radiosensitizing effect of JNC-1043. Each IC50 values of DLD-1 and HCT116 cell lines were calculated as 0.157, 0.1145, respectively. Cell counting assays were performed and then showed combination of JNC-1043 and γ-ionizing radiation (IR) enhanced cell death. JNC-1043 only- or IR only-treatment induced cell death by 50~60%, respectively, while combination of JNC-1043 and IR increased more 20~30% cell death than those of JNC-1043 only- or IR only-treatment in both cell lines. Clonogenic assay also performed, and then dose enhancement ratios (DER) of DLD-1 and HCT116 were calculated as 1.40, 1.53, respectively. Apoptosis also was detected with Annexin V-Propidium iodide assay. Combination of JNC-1043 and IR increased apoptosis more 30~40% than those of JNC-1043 only- or IR only-treatment. DCFDA-based assay also were performed to indicate ROS production was enhanced in combination of JNC-1043 and IR. In vivo xenograft experiment, combination of JNC-1043 and IR reduced tumor sizes less 50% and increased apoptosis more 30~40% than those of JNC-1043 only- or IR only-treatment. These results implied anti-cancer and radiosensitizing effect of JNC-1043 resulted from promotion of apoptosis via enhancement of ROS production. Citation Format: Jong Kuk Park, A-Ram Kang, Jin-Hee Kwon, Jong-Ryoo Choi, Jie-Young Song, Sang-Gu Hwang. Novel β-Apopicropodophyllin derivative, JNC-1043, exerts anti-cancer and radiosensitizing effects [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6061.

The Effect of Pregnancy and Inflammatory Bowel Disease on the Pharmacokinetics of Drugs Related to Inflammatory Bowel Disease-A Systematic Literature Review.

Due to ethical and practical reasons, a knowledge gap exists on the pharmacokinetics (PK) of inflammatory bowel disease (IBD)-related drugs in pregnant women with IBD. Before evidence-based dosing can be proposed, insight into the PK has to be gained to optimize drug therapy for both mother and fetus. This systematic review aimed to describe the effect of pregnancy and IBD on the PK of drugs used for IBD. One aminosalicylate study, two thiopurine studies and twelve studies with biologicals were included. Most drugs within these groups presented data over multiple moments before, during and after pregnancy, except for mesalazine, ustekinumab and golimumab. The studies for mesalazine, ustekinumab and golimumab did not provide enough data to demonstrate an effect of pregnancy on concentration and PK parameters. Therefore, no evidence-based dosing advice was given. The 6-thioguanine nucleotide levels decreased during pregnancy to 61% compared to pre-pregnancy levels. The potentially toxic metabolite 6-methylmercaptopurine (6-MMP) increased to maximal 209% of the pre-pregnancy levels. Although the PK of the thiopurines changed throughout pregnancy, no evidence-based dosing advice was provided. One study suggested that caution should be exercised when the thiopurine dose is adjusted, due to shunting 6-MMP levels. For the biologicals, infliximab levels increased, adalimumab stayed relatively stable and vedolizumab levels tended to decrease during pregnancy. Although the PK of the biologicals changed throughout pregnancy, no evidence-based dosing advice for biologicals was provided. Other drugs retrieved from the literature search were mesalazine, ustekinumab and golimumab. We conclude that limited studies have been performed on PK parameters during pregnancy for drugs used in IBD. Therefore, more extensive research to determine the values of PK parameters is warranted. After gathering the PK data, evidence-based dosing regimens can be developed.

Pengaruh Pemberian Omeprazole Terhadap Profil Farmakokinetika Piroxicam Dengan Metode Kromatografi Cair Kinerja Tinggi (KCKT)

Piroxicam is an anti-inflammatory drug belonging to the NSAID group and is also used as an analgesic and anti-rheumatic drug. Its use is often combined with stomach medicines, as the side effects of piroxicam can irritate the stomach. One of them is omeprazole. Since piroxicam and omeprazole act on the same enzyme, CYP450, they can affect the pharmacokinetic profile, especially at the metabolic stage and excretion of piroxicam. The purpose of this study was to determine the effect of omeprazole on the pharmacokinetic profile of piroxicam especially in the metabolic phase and excretion. The method used in this study was an experimental method using three male rabbits. These rabbits are divided into three groups. The first treatment group was giving pyroxicam solution 0.653 mg / kg body weight, the second treatment group gave piroxicam 0.653 mg / kg body weight that one hour before was given omeprazole 1.2 mg / kg body weight and the third group treated with piroxicam 0.7 mg / kg body weight at the same time with omeprazole 1,4 mg / kg body weight. Plasma levels of the drug piroxicam are measured using a high performance liquid chromatography (HPLC) tool. The verification method is executed. This is the determination of LOD and LOQ values, accuracy and accuracy testing. The result of data analysis using t-table. The results showed that there was an increase or difference in pharmacokinetic parameter values ​​during the absorption phase, but no significant effect was shown for each group. Pharmacokinetic parameter values ​​for metabolic stages and excretion were reduced and no significant difference was shown between the groups. Simultaneous administration of omeprazole and piroxicam and administration of piroxicam 1 hour before omeprazole may inhibit piroxicam-metabolizing enzymes and thus affect pharmacokinetic parameters and excretion during absorption, but are not significant.&#x0D;

A randomized, crossover, phase I clinical study to evaluate bioequivalence and safety of tofacitinib and Xeljanz® in Chinese healthy subjects

ObjectiveTofacitinib is an oral Janus kinase (JAK) inhibitor that has been marketed and approved in the USA for the clinical treatment of rheumatoid arthritis, psoriasis and other inflammatory and autoimmune diseases. A phase I clinical trial was conducted to compare the bioequivalence and safety of tofacitinib (Chia Tai Tianqing Pharmaceutical Group Co., Ltd.) and Xeljanz® (Pfizer Inc.) in healthy Chinese subjects, providing basis for the clinical application of tofacitinib. MethodsHealthy Chinese subjects (N = 32) were randomly assigned to two groups at a 1:1 ratio. Subjects orally took 5 mg tofacitinib or Xeljanz® per cycle in random sequence. Blood samples were collected at 15 sampling points per cycle, and plasma drug concentrations of tofacitinib or Xeljanz® were analyzed by liquid chromatography–tandem mass spectrometry (LC–MS/MS) and statistical analysis for the pharmacokinetic (PK) parameters. Subjects' physical indicators were monitored during the whole process to evaluate drug safety. ResultsThe adjusted geometric mean ratios (GMRs) of the peak concentration (Cmax), area under the curve (AUC) from time zero to the last measurable concentration (AUC0-t) and AUC from time zero to observed infinity (AUC0-∞) were all within the range of 80–125%. The other PK parameter values were similar. The above values were all meeting the bioequivalence criteria with well safety. ConclusionThe pharmacokinetic parameters and safety profile of tofacitinib were similar to those of Xeljanz® in healthy Chinese subjects. Therefore, tofacitinib can be considered bioequivalent to Xeljanz®, and the findings of this trial will promote the clinical application of tofacitinib.

Evaluation of the relationship between polymorphisms in CYP2C19 and the single-dose pharmacokinetics of omeprazole in healthy Chinese volunteers: A multicenter study.

The aim of this study was to evaluate the relationship between polymorphisms in CYP2C19 and the single‐dose pharmacokinetics (PKs) of omeprazole in healthy Chinese volunteers. A 20 mg single dose of omeprazole (Losec) enteric‐coated capsules or tablets was orally administered to 656 healthy subjects from eight subcenters. The polymorphic alleles of CYP2C19*2, *3, and *17 were determined by Sanger sequencing and Agena mass array. Plasma concentrations of omeprazole were determined by high‐performance liquid‐chromatography tandem mass spectrometry. PK parameters of area under the concentration versus time curve (AUC)0‐t, AUC from zero to infinity (AUC0‐∞), maximum plasma concentration (Cmax), and terminal half‐life (t1/2) were significantly influenced by CYP2C19 phenotype (all p < 0.001) and diplotype (all p < 0.001), and the same results were obtained in the subgroup analysis of the effects of diet and dosage form. The polymorphisms of CYP2C19*2(rs4244285; all PK parameters p < 0.001) and *3(rs4986893; p Cmax = 0.020, and the p values of other PK parameters were less than 0.001) were significantly associated with the PKs of omeprazole. For CYP2C19*17 (rs12248560), only t1/2 showed a significant correlation (p = 0.032), whereas other PK parameters did not. The present study demonstrated that the Pks of omeprazole is greatly influenced by CYP2C19.

"De-Shrinking" EBEs: The Solution for Bayesian Therapeutic Drug Monitoring.

BackgroundTherapeutic drug monitoring (TDM) aims at individualising a dosage regimen and is increasingly being performed by estimating individual pharmacokinetic parameters via empirical Bayes estimates (EBEs). However, EBEs suffer from shrinkage that makes them biased. This bias is a weakness for TDM and probably a barrier to the acceptance of drug dosage adjustments by prescribers.ObjectiveThe aim of this article is to propose a methodology that allows a correction of EBE shrinkage and an improvement in their precision.MethodsAs EBEs are defined, they can be seen as a special case of ridge estimators depending on a parameter usually denoted λ. After a bias correction depending on λ, we chose λ so that the individual pharmacokinetic estimations have minimal imprecision. Our estimate is by construction always better than EBE with respect to bias (i.e. shrinkage) and precision.ResultsWe illustrate the performance of this approach with two different drugs: iohexol and isavuconazole. Depending on the patient’s actual pharmacokinetic parameter values, the improvement given by our approach ranged from 0 to 100%.ConclusionThis innovative methodology is promising since, to the best of our knowledge, no other individual shrinkage correction has been proposed.

Drug levels, anti-drug antibodies and B-cell counts were not predictive of response in rheumatoid arthritis patients on (ultra-)low-dose rituximab.

The REDO trial (REtreatment with Rituximab in RhEumatoid arthritis: Disease Outcome after Dose Optimisation) showed that ultra-low-dose rituximab (500 mg or 200 mg) was similarly effective to a 1000 mg dosage in the majority of RA patients. This pre-planned secondary analysis investigated (1) associations between rituximab dosage, drug levels, anti-drug antibodies (ADAs) and B-cell counts and (2) the predictive value of pharmacokinetic and pharmacodynamic parameters, and of patient, disease and treatment characteristics in relation to response to ultra-low-dose rituximab. For 140 RA patients from the REDO trial, differences in drug levels, ADAs and B-cell counts were examined at baseline, and at 3 and 6 months after dosing. Treatment response was defined as absence of flare and no extra rituximab or >1 glucocorticoid injection received during follow-up. The association between potential predictors and response was investigated using logistic regression analyses. Lower doses of rituximab resulted in lower drug levels but did not significantly affect ADA levels or B-cell counts, and 3 (10.7%), 12 (20.7%) and 7 (13.0%) patients failed to meet the response criteria in, respectively, the 1000 mg, 500 mg and 200 mg dosage groups. Drug levels, ADAs, B-cell counts, and patient, disease and treatment characteristics were not predictive for response to ultra-low-dose rituximab. The results of this study further support the hypothesis that continued treatment with 500 or 200 mg rituximab is similarly effective to a 1000 mg dosage in RA patients doing well on rituximab. These results, combined with lack of finding a clinical dose-response relationship in the original REDO study, suggest that 200 mg rituximab is not yet the lowest effective rituximab retreatment dose in RA.

Population Pharmacokinetics of Meropenem in Preterm Infants

Background. Meropenem, a broad spectrum carbapenem antibiotic, is often used for newborns despite of limited data available on neonatal pharmacokinetics. Due to pharmacokinetic and pharmacodynamic differences as well as to significant changes in the human body related to growth and maturation of organs and systems, direct scaling and dosing extrapolation from adults or older children with adjustment on patients weight can result in increased risk of toxicity or treatment failures. Aims to evaluate the pharmacokinetics of meropenem in premature neonates based on therapeutic drug monitoring data in real clinical settings. Materials. Of 53 pre-term neonates included in the pharmacokinetic/pharmacodynamic analysis, in 39 (73.6%) patients, gestational age ranged from 23 to 30 weeks. Population and individual pharmacokinetic parameter values were estimated by the NPAG program from the Pmetrics package based on peak-trough therapeutic drug monitoring. Samples were assayed by high-performance liquid chromatography. One-compartment pharmacokinetic model with zero-order input and first-order elimination was used to fit concentration data and to predict pharmacokinetic parameter (%T MIC of free drug) for virtual patients with simulated fast, moderate and slow meropenem elimination received different dosage by minimum inhibitory concentration (MIC) level. Univariate and multivariate regression analysis was used to evaluate the influence of patients covariates (gestational age, postnatal age, postconceptual age, body weight, creatinine clearance calculated by Schwartz formula, etc) on estimated meropenem pharmacokinetic parameters. Results. The identified population pharmacokinetic parameters of meropenem in pre-term newborns (elimination half-lives T1/2 = 1.93 0.341 h; clearance CL = 0.26 0.085 L/h/ kg; volume of distribution V = 0.71 0.22 L/h) were in good agreement with those published in the literature for adults, neonates and older children. Pharmacokinetic/pharmacodynamic modeling demonstrated that a meropenem dosage regimen of 90 mg/kg/day administered using prolonged 3-hour infusion every 8 hours should be considered as potentially effective therapy if nosocomial infections with resistant organisms (MIC 8 mg/L) are treated. Conclusions. Neonates and especially pre-term neonates have a great pharmacokinetic variability. Meropenem dosing in premature newborns derived from population pharmacokinetic/pharmacodynamic model can partly overcome the variability, but not all pharmacokinetic variability can be explained by covariates in a model. Further personalizing based on Bayesian forecasting approach and a patients therapeutic drug monitoring data can help to achieve desired pharmacodynamic target.

Bioequivalence Study of Palbociclib Capsules in Healthy Chinese Subjects Under Fasting and Fed Conditions.

Palbociclib is an oral small-molecule inhibitor of cyclin-dependent kinase 4/6 used for the treatment of advanced breast cancer. This study compared the pharmacokinetic and safety profiles between a new generic and a branded reference formulation of palbociclib capsules in healthy Chinese subjects under fasting and fed conditions and evaluated the bioequivalence of two palbociclib products to obtain sufficient evidence for the marketing approval of the new generic drug. A randomized, open-label, two-period crossover study was conducted in healthy Chinese volunteers under both fasting and fed conditions (30 subjects/condition). Eligible healthy subjects received a single 125-mg dose of the palbociclib test or reference formulation followed by a 14-day washout period. Serial blood samples were collected at scheduled timepoints, and plasma concentrations were determined by a validated high-performance liquid chromatography-tandem mass spectrometry method. A non-compartment method was used to calculate the main pharmacokinetic parameters, including the area under the plasma concentration-time curve(AUC) from time 0 to the time of the last measurable concentration (AUC0-t), the AUC from time 0 to infinity (AUC0-∞), the maximum plasma concentration(Cmax), the time to maximum plasma concentration, and the elimination half-life. The geometric mean ratios and the corresponding 90% confidence intervals of palbociclib were acquired for the bioequivalence analysis. Safety and tolerability were assessed by monitoring adverse events, laboratory assessments, vital signs, physical examinations, and 12-lead electrocardiograms. Under the fasting condition, the pharmacokinetic parameter values of the test formulation were similar to those of the reference formulation. The 90% confidence intervals of geometric mean ratios of the test to reference formulations were 94.35-103.82% for Cmax, 94.79-103.26% for AUC0-t, and 94.82-103.38% for AUC0-∞, which are all within the accepted bioequivalence range of 80.00-125.00%. Meanwhile, under the fed condition, the pharmacokinetic parameter values of the test formulation were also similar to those of the reference formulation. The 90% confidence intervals of geometric mean ratios of the test to reference formulations were 96.65-103.56% for Cmax, 98.06-103.61% for AUC0-t, and 97.88-103.46% for AUC0-∞, which are all within the accepted bioequivalence range of 80.00-125.00%. The test and reference products were well tolerated, and no serious adverse events occurred during the study. Pharmacokinetic bioequivalence of palbociclib in healthy subjects was established between the palbociclib test formulation and the reference formulation under fasting and fed conditions according to predetermined regulatory criteria. The two formulations were safe and well tolerated.

Optimisation of cilnidipine nanoparticles using box-behnken design: in-vitro, toxicity and bioavailability assessment

ABSTRACT Cilnidipine is an antihypertensive drug with low solubility and poor bioavailability. This study aimed to formulate and optimise nanoparticles to improve the solubility, drug release and bioavailability of cilnidipine. The cilnidipine nanoparticles were prepared by the anti-solvent precipitation-ultrasound technology and optimised by a 3-factor, 3-level Box- Behnken design. Particle size and zeta potential of the cilnidipine nanoparticles were 60 ± 7.18 nm and -14.5 ± 4.12 mV, respectively. A greater value of pharmacokinetic parameters–maximum plasma concentration and area under curve has indicated better drug absorption in the form of nanoparticles. The value of half-life of cilnidipine nanoparticles (1.2 h) decreased compared to the drug (2.4 h),which concluded that, the increased absorption of cilnidipine nanoparticles. These findings reinforce that the formulation of nanoparticles is a new approach for solubility and bioavailability enhancement of cilnidipine.

Spatiotemporal imaging and pharmacokinetics of fluorescent compounds in zebrafish eleuthero-embryos after different routes of administration

Zebrafish (Danio rerio) is increasingly used to assess the pharmacological activity and toxicity of compounds. The spatiotemporal distribution of seven fluorescent alkyne compounds was examined during 48 h after immersion (10 µM) or microinjection (2 mg/kg) in the pericardial cavity (PC), intraperitoneally (IP) and yolk sac (IY) of 3 dpf zebrafish eleuthero-embryos. By modelling the fluorescence of whole-body contours present in fluorescence images, the main pharmacokinetic (PK) parameter values of the compounds were determined. It was demonstrated that especially in case of short incubations (1–3 h) immersion can result in limited intrabody exposure to compounds. In this case, PC and IP microinjections represent excellent alternatives. Significantly, IY microinjections did not result in a suitable intrabody distribution of the compounds. Performing a QSPkR (quantitative structure-pharmacokinetic relationship) analysis, LogD was identified as the only molecular descriptor that explains the final uptake of the selected compounds. It was also shown that combined administration of compounds (immersion and microinjection) provides a more stable intrabody exposure, at least in case of a prolonged immersion and compounds with LogD value > 1. These results will help reduce the risk of false negative results and can offer an invaluable input for future translational research and safety assessment applications.

Pharmacokinetic Changes According to Single or Multiple Oral Administrations of Socheongryong-Tang to Rats: Presented as a Typical Example of Changes in the Pharmacokinetics Following Multiple Exposures to Herbal Medicines.

The purpose of this study was to investigate the pharmacokinetic properties of ephedrine, paeoniflorin, and cinnamic acid after single or multiple doses of Socheongryong-tang (SCRT) were administered to rats, and to present an example of the pharmacokinetic changes following multiple doses of an herbal medicine. SCRT is a traditional herbal medicine that has been used clinically for a long time, and its main ingredients include ephedrine, paeoniflorin, and cinnamic acid. However, studies on the pharmacokinetic properties of SCRT are insufficient, and particularly, no pharmacokinetic information has been reported for multiple doses. In this study, SCRT was administered orally to rats once or multiple times, and plasma sampled at different times was quantitatively analyzed for ephedrine, paeoniflorin, and cinnamic acid using ultra-high-performance liquid chromatography-tandem mass spectrometry. There was a difference between the pharmacokinetic parameter values of each component (especially in paeoniflorin and cinnamic acid) obtained after single or multiple doses of SCRT. The actual observed values of each component obtained after multiple doses of SCRT were clearly different from the predicted results of multiple-dose simulations based on the pharmacokinetic profiles obtained after a single dose. The results confirmed that the plasma concentrations and, thus, exposures to paeoniflorin and cinnamic acid were significantly increased when SCRT was administered multiple times, whereas that of ephedrine was not. The results of this study are expected to provide useful pharmacokinetic data for the safety and efficacy evaluation of SCRT in the future and demonstrate the necessity of pharmacokinetic comparison studies according to single or multiple oral administrations of herbal medicines.