Real-Time Particle Emission Monitoring for the Non-Invasive Prediction of Lung Deposition via a Dry Powder Inhaler.

Although inhalation therapy represents a promising drug delivery route for the treatment of respiratory diseases, the real-time evaluation of lung drug deposition remains an area yet to be fully explored. To evaluate the utility of the photo reflection method (PRM) as a real-time non-invasive monitoring of pulmonary drug delivery, the relationship between particle emission signals measured by the PRM and in vitro inhalation performance was evaluated in this study. Symbicort® Turbuhaler® was used as a model dry powder inhaler. In vitro aerodynamic particle deposition was evaluated using a twin-stage liquid impinger (TSLI). Four different inhalation patterns were defined based on the slope of increased flow rate (4.9-9.8 L/s2) and peak flow rate (30 L/min and 60 L/min). The inhalation flow rate and particle emission profile were measured using an inhalation flow meter and a PRM drug release detector, respectively. The inhalation performance was characterized by output efficiency (OE, %) and stage 2 deposition of TSLI (an index of the deagglomerating efficiency, St2, %). The OE × St2 is defined as the amount delivered to the lungs. The particle emissions generated by four different inhalation patterns were completed within 0.4 s after the start of inhalation, and were observed as a sharper and larger peak under conditions of a higher flow increase rate. These were significantly correlated between the OE or OE × St2 and the photo reflection signal (p < 0.001). The particle emission signal by PRM could be a useful non-invasive real-time monitoring tool for dry powder inhalers.

Association of direct oral anticoagulant and delayed bleeding with pharmacokinetics after endoscopic submucosal dissection.

BACKGROUND AND AIMS: Pharmacokinetic parameters, such as drug plasma level at trough, time to maximum plasma concentration (Tmax), and coagulation factor Xa (FXa) activity generally predict factors for the anticoagulant effects of direct oral anticoagulants (DOACs). Although GI bleeding is a major adverse event after endoscopic submucosal dissection (ESD), little is known about the association between post-ESD bleeding in patients taking DOACs and the pharmacologic parameters. This study aimed to evaluate pharmacologic risk factors for post-ESD bleeding in patients taking DOACs. METHODS: We prospectively evaluated the incidence of post-ESD bleeding in patients taking DOACs between April 2018 and May 2022 at 21 Japanese institutions and investigated the association with post-ESD bleeding and pharmacologic factors, including plasma concentration and FXa activity at trough and Tmax. RESULTS: The incidence of post-ESD bleeding was 12.8% (14 of 109; 95% confidence interval [CI], 7.2-20.6). Although plasma DOAC concentration and plasma level/dose ratio at trough and Tmax varied widely among individuals, a significant correlation with plasma concentration and FXa activity was observed (apixaban: correlation coefficient, -0.893; P < .001). On multivariate analysis, risk factors for post-ESD bleeding in patients taking DOACs were higher age (odds ratio [OR], 1.192; 95% CI, 1.020-1.392; P = .027) and high anticoagulant ability analyzed by FXa activity at trough and Tmax (OR, 6.056; 95% CI, 1.094-33.529; P = .039). CONCLUSIONS: The incidence of post-ESD bleeding in patients taking DOACs was high, especially in older patients and with high anticoagulant effects of DOACs. Measurement of pharmacokinetic parameters of DOACs may be useful in identifying patients at higher risk of post-ESD bleeding.

Decreased Analgesic Effect of Tramadol in Japanese Patients with CYP2D6 Intermediate Metabolizers after Orthopedic Surgery.

Tramadol is metabolized by CYP2D6 to an active metabolite, which in turn acts as an analgesic. This study aimed to investigate the impact of CYP2D6 genotype on the analgesic effect of tramadol in clinical practice. A retrospective cohort study was performed in patients treated with tramadol for postoperative pain after arthroscopic surgery for rotator cuff injury during April 2017-March 2019. The impact of CYP2D6 genotypes on the analgesic effects was assessed by the numeric rating scale (NRS) pain scoring and analyzed by the Mann-Whitney U test. Stepwise multiple linear regression analysis was performed to identify predictive factors for the area under the time-NRS curve (NRS-AUC), which was calculated using the linear trapezoidal method. Among the 85 enrolled Japanese patients, the number of phenotypes with CYP2D6 normal metabolizer (NM) and intermediate metabolizer (IM) was n = 69 (81.1%) and n = 16 (18.9%), respectively. The NRS and NRS-AUC in the IM group were significantly higher than those in the NM group until Day 7 (p < 0.05). The multiple linear regression analysis indicated that the CYP2D6 polymorphism was a prediction factor of the high NRS-AUC levels in Days 0-7 (ß = 9.52, 95% CI 1.30-17.7). In IM patients, the analgesic effect of tramadol was significantly reduced one week after orthopedic surgery in clinical practice. Therefore, dose escalation of tramadol or the use of alternative analgesic medications can be recommended for IM patients.

Attenuation of phenobarbital-induced cytochrome P450 expression in carbon tetrachloride-induced hepatitis in mice models.

Certain pathological conditions, such as inflammation, are known to affect basal cytochrome P450 (CYP) expression by modulating transcriptional regulation, and the pharmacokinetics of drugs can vary among patients. However, changes in drug-induced CYP expression under pathological conditions have not been elucidated in detail. Here, we investigated the effects of hepatic inflammation and injury on phenobarbital-induced expression of CYP isoforms in mice. Phenobarbital was administered once as a CYP inducer in the carbon tetrachloride-induced hepatitis model mice. The mRNA expression levels of Cyp3a11 and Cyp2b10 in the liver and small intestine were measured using reverse transcription polymerase chain reaction. The enzymatic activity of CYP3A in liver S9 was evaluated using midazolam as the substrate. Phenobarbital increased the mRNA expression of Cyp3a11 and Cyp2b10 in the liver of healthy mice, but not in the small intestine. Increased mRNA expression of hepatic Cyp3a11 and Cyp2b10 by phenobarbital was significantly suppressed in the hepatitis model mice. Hepatitis also suppressed the increased CYP3A enzymatic activity induced by phenobarbital in liver S9, consistent with the results of Cyp3a11 mRNA expression. These results suggest that the inducibility of CYP by phenobarbital may vary in patients with hepatitis, indicating that pharmacokinetic drug-drug interactions can be altered under certain pathological conditions.

Changes in the expression of drug-metabolising enzymes and drug transporters in mice with collagen antibody-induced arthritis.

1. We investigated the changes in the expression of drug-metabolising enzymes and drug transporters in the liver, small intestine and kidney of mice with collagen antibody-induced arthritis (CAIA) to determine whether changes in these expressions affect pharmacokinetics of drugs in patients with rheumatoid arthritis.2. mRNA expression levels of cytochrome P450 (Cyp) 2b10, Cyp2c29 and Cyp3a11 were observed to be lower in the liver and small intestine of CAIA mice than in control mice. Compared with control mice, mRNA expression levels of multidrug resistance 1 b, peptide transporter 2 and organic anion transporter (Oat) 2 were high in the liver of CAIA mice. Changes in these expression levels were different among organs. However, elevated expression of Oat2 mRNA was not associated with an increase in protein expression and transport activity evaluated using [3H]cGMP as a substrate.3. These results suggest that arthritis can change the expression of pharmacokinetics-related genes, but the changes may not necessarily be linked to the pharmacokinetics in patients with rheumatoid arthritis. On the other hand, we found Oat2 mRNA expression level was positively correlated with plasma interleukin-6 level, indicating that transcriptional activation of Oat2 may occur in inflammatory state.

Effects of antiepileptic drugs' administration during pregnancy on the nerve cell proliferation and axonal outgrowth of human neuroblastoma SH-SY5Y nerve cells.

It has been suggested that the intelligence quotient of children born to pregnant women taking 1000 mg or more of valproic acid per day is lower than that of children born to pregnant women taking other antiepileptic drugs. However, the mechanism whereby intelligence quotient is decreased in children exposed to valproic acid during the fetal period has not yet been elucidated. Therefore, we used the human neuroblastoma cell line SH-SY5Y to evaluate the effects of antiepileptic drugs containing valproic acid on nerve cells. We assessed the anti-proliferative effects of drugs in these cells via WST-8 colorimetric assay, using the Cell Counting Kit-8. We also quantified drug effects on axonal elongation from images using ImageJ software. We also evaluated drug effects on mRNA expression levels on molecules implicated in nervous system development and folic acid uptake using real-time PCR. We observed that carbamazepine and lamotrigen were toxic to SH-SY5Y cells at concentrations >500 µM. In contrast, phenytoin and valproic acid were not toxic to these cells. Carbamazepine, lamotrigen, phenytoin, and valproic acid did not affect axonal outgrowth in SH-SY5Y cells. Sodium channel neuronal type 1a (SCN1A) mRNA expression-level ratios increased when valproic acid was supplemented to cells. The overexpression of SCN1A mRNA due to high valproic acid concentrations during the fetal period may affect neurodevelopment. However, since detailed mechanisms have not yet been elucidated, it is necessary to evaluate it by comparing cell axon elongation and SCN1A protein expression due to high-concentration valproic acid exposure.

Incorrect Holding Angle of Dry Powder Inhaler during the Drug-Loading Step Significantly Decreases Output Efficiency.

It is well known that correct use of inhalers plays a critical role in optimal inhalation therapy, but the impact of incorrect inhaler use on pulmonary drug delivery has not been quantitatively evaluated. The aim of this study was to investigate the frequency of holding inhalers at incorrect angles during the drug-loading step while using Turbuhaler® and to quantify the influence of the inhaler angle on in vitro pulmonary delivery. Thirty patients prescribed Turbuhaler® at Shiga University of Medical Science Hospital were enrolled. During inhalation, the participants' inhalation techniques were assessed by clinical pharmacists. Additionally, the influence of the inhaler angle on pulmonary delivery of budesonide via Symbicort® Turbuhaler® was investigated using a Twin-Stage Liquid Impinger. Output efficiency (OE), stage 2 deposition (St2), and OE × St2 were calculated. An incorrect angle during the drug-loading step was observed in 33.3% of the participants. In vitro testing demonstrated that OE, an index of the loaded dose, significantly decreased by 73.3% at an incorrect angle, while St2, an index of the deagglomerating efficiency, was stable independent of the holding angle. OE × St2, indicating the bronchial and pulmonary drug delivery amount, decreased by 76.9%. An incorrect holding angle reduced the loaded dose, resulting in decreased pulmonary delivery. Error in the inhaler angle occurs frequently and demonstrates a considerable impact on pulmonary drug delivery. Hence, it is necessary to assess the Turbuhaler® angle during inhalation.

High incidence of major bleeding with off-label use of edoxaban.

In clinical practice, edoxaban is sometimes prescribed for off-label use based on the hypothesis that it is as safe and effective as warfarin. However, there is limited safety information on off-label use due to lack of clinical trial. We aimed to analyze the tolerability of off-label use of edoxaban and to identify patient characteristics associated with major bleeding as adverse effects. Patients under edoxaban treatment between January 2017 and December 2017 were enrolled in this retrospective cohort study. The incidence of major bleeding with off-label use compared with on-label use was analyzed using by log-rank test. Univariate and multivariate regression analysis were undertaken to detect independent variables with significant odds ratio that associated with major bleeding. After the exclusion criteria were applied, the patients were divided into two groups: off-label group (n = 30) and on-label group (n = 161). Incidence of major bleeding was found to be higher in the off-label group (13.3%) than in the on-label group (3.7%) (p<0.05). Multivariate adjustment showed that the off-label use or portal vein thrombosis and patients with history of major bleeding has significantly higher incidence of major bleeding. We demonstrated that off-label use of edoxaban may be a significant risk factor for major bleeding.

Is "Slow Inhalation" Always Suitable for Pressurized Metered Dose Inhaler?

To achieve adequate inhalation therapy, a proper inhalation technique is needed in clinical practice. However, there is limited information on proper inhalation flow patterns of commercial inhalers. Here, we quantitatively estimated airway deposition of two commercial pressurized metered dose inhalers (pMDIs) to determine their optimal inhalation patterns. Sultanol® inhaler (drug particles suspended in a propellant, suspension-pMDI) and QVAR™ (drug dissolved in a propellant with ethanol, solution-pMDI) were used as model pMDIs. Aerodynamic properties of the two pMDIs were determined using an Andersen cascade impactor with human inhalation flow simulator developed by our laboratory. As indices of peripheral-airway drug deposition, fine particle fractions (FPFPA) at different inhalation flow rates were calculated. The time-dependent particle diameters of sprayed drug particles were determined by laser diffraction. On aerodynamic testing, FPFPA of suspension-pMDI significantly decreased depending on the increasing inhalation flow rate, while solution-pMDI achieved higher and constant FPFPA in the range of the tested inhalation flow rates. The particle diameter of solution-pMDI markedly decreased from 5 to 3 µm in a time-dependent manner. Conversely, that of suspension-pMDI remained at 4 µm during the spraying time. Although "slow inhalation" is recommended for pMDIs, airway drug deposition via solution-pMDI (extra-fine particles) is independent of patients' inhalation flow pattern. Clinical studies should be performed to validate instruction for use of pMDIs for each inhaler for the optimization of inhalation therapy.

Population pharmacokinetics and pharmacogenomics of apixaban in Japanese adult patients with atrial fibrillation.

AIMS: This study aimed to analyse the effects of genetic polymorphisms in drug transporters and metabolizing enzymes, and clinical laboratory data on the pharmacokinetic parameters of apixaban. METHODS: Data were collected from 81 Japanese patients with atrial fibrillation. Pharmacogenomic data were stratified by ABCB1, ABCG2 and CYP3A5 polymorphisms. The pharmacokinetic profile of apixaban was described by a one-compartment model with first-order absorption. Population pharmacokinetic analysis was conducted using a nonlinear mixed effect modelling (NONMEM™) program. RESULTS: The nonlinear relationship between oral clearance (CL/F) of apixaban and creatinine clearance (Ccr) was observed. The population mean of CL/F for a typical patient (Ccr value of 70 ml min-1 ) with the CYP3A5*1/*1 and ABCG2 421C/C or C/A genotypes was estimated to be 3.06 l h-1 . When Ccr values were set to the typical value, the population mean of CL/F was 1.52 times higher in patients with the CYP3A5*1/*1 genotype compared with patients with the CYP3A5*1/*3 or *3/*3 genotype, while the population mean of CL/F was 1.49 times higher in patients with the ABCG2 421C/C or C/A genotype compared with patients with the ABCG2 421A/A genotype. However, no covariates affected the population mean of the apparent volume of distribution (Vd/F) of apixaban. The population mean of Vd/F was estimated to be 24.7 l. CONCLUSION: The present study suggests that the ABCG2 421A/A and CYP3A5*3 genotypes and renal function are intrinsic factors affecting apixaban pharmacokinetics. These findings may provide useful information for precision medicine using apixaban, to avoid the risk of adverse reactions.

Impact of ABCB1, ABCG2, and CYP3A5 polymorphisms on plasma trough concentrations of apixaban in Japanese patients with atrial fibrillation.

OBJECTIVES: During anticoagulant therapy, major bleeding is one of the most severe adverse effects. This study aimed to evaluate the relationships between ABCB1, ABCG2, and CYP3A5 polymorphisms and plasma trough concentrations of apixaban, a direct inhibitor of coagulation factor X. PATIENTS AND METHODS: A total of 70 plasma concentrations of apixaban from 44 Japanese patients with atrial fibrillation were analyzed. In these analyses, the plasma trough concentration/dose (C/D) ratio of apixaban was used as a pharmacokinetic index and all data were stratified according to the presence of ABCB1 (ABCB1 1236C>T, 2677G>T/A, and 3435C>T), ABCG2 (ABCG2 421C>A), and CYP3A5 (CYP3A5*3) polymorphisms. Influences of various clinical laboratory parameters (age, serum creatinine, estimated glomerular filtration rate, aspartate amino transferase, and alanine amino transferase) on the plasma trough C/D ratio of apixaban were included in analyses. RESULTS: Although no ABCB1 polymorphisms affected the plasma trough C/D ratio of apixaban, the plasma trough C/D ratio of apixaban was significantly higher in patients with the ABCG2 421A/A genotype than in patients with the ABCG2 421C/C genotype (P<0.01). The plasma trough C/D ratio of apixaban in patients with CYP3A5*1/*3 or *3/*3 genotypes was also significantly higher than that in patients with the CYP3A5*1/*1 genotype (P<0.05). Furthermore, the plasma trough C/D ratio of apixaban decreased with increased estimated glomerular filtration rate. CONCLUSION: These results indicate that ABCG2 421A/A and CYP3A5*3 genotypes and renal function are considered potential factors affecting trough concentrations of apixaban.

Interspecies comparison of hepatic metabolism of six newly synthesized retinoid X receptor agonistic compounds possessing a 6-[N-ethyl-N-(alkoxyisopropylphenyl)amino]nicotinic acid skeleton in rat and human liver microsomes.

OBJECTIVE: The hepatic metabolism of six compounds newly synthesized as retinoid X receptor agonists was characterized in rat and human liver microsomes to examine the relationship between their hepatic metabolism profiles and side chain structures, considering the interspecies difference. MATERIALS AND METHODS: The compounds used have a 6-[N-ethyl-N-(3-alkoxy-4-isopropylphenyl)amino]nicotinic or 6-[N-ethyl-N-(4-alkoxy-3-isopropylphenyl)amino]nicotinic acid skeleton, in which the isopropoxy, isobutoxy or cyclopropylmethoxy group is employed for the alkoxy group. These compounds were incubated with the microsomes, and their Michaelis--Menten parameters were determined. The incubation study was also performed with various cytochrome P450 (CYP) inhibitors to examine their susceptibilities to the inhibitors. In addition, a molecular docking simulation was conducted to assess the compound's spatial configuration with the CYP isoform when necessary. RESULTS: The Michaelis--Menten parameters determined are comparable between rats and humans for the compounds having 3-isobutoxy, 4-isobutoxy, 4-isopropoxy and 4-cyclopropylmethoxy groups. However, it was indicated that all compounds except that having the 3-isobutoxy group are metabolized in a different manner between rats and humans. That is, the extent of the contribution of each CYP isozyme is different between those two species. A molecular docking simulation showed that the spatial configuration of the compound to be associated with CYP2D6 markedly changes depending on whether the isobutoxy group is situated at the 3- or 4-position. CONCLUSION: A slight difference in the side chain structures markedly alters the compound's metabolic profile, which amplifies the interspecies difference regarding the profile, increasing the difficulty in characterizing the profile in humans with the structural-property relationship and interspecies extrapolation.

Potential treatment option of rivaroxaban for breastfeeding women: A case series.

The use of direct oral anticoagulants (DOACs) in breastfeeding women is currently challenging due to limited safety data for breastfeeding infants, and there have been no previous studies on the drug concentration in breastfeeding infants. We treated 2 patients (one case was twin pregnancy) with venous thromboembolisms in breastfeeding women administered rivaroxaban at our institution. Blood samples from the mothers and breastmilk samples were collected at time 0 and 2 h after the rivaroxaban administration, breastfeeding was conducted 2 h after the rivaroxaban administration, and blood samples from the infants were collected 2 h after breastfeeding (4 h after maternal rivaroxaban administration). The milk-to-plasma (M:P) ratios were 0.27 in Case 1 and 0.32 in Case 2. The estimated relative infant dose (RID) was 0.82 % in Case 1 Children 1 and 2, and 1.27 % in Case 2. The rivaroxaban concentration in the infant plasma was below the lower limit of quantification in all infants. In addition, even in the high-exposure case simulation based on 5 days of breastfeeding in Case 2, the infant plasma concentration level was below the lower limit of quantification. At 3 months of follow-up, breastfeeding was continued, and all infants grew and developed without any health problems including bleeding events. The current case series showed that there were no pharmacokinetic or clinical concerns for breastfeeding women or breastfed infants, and provides support for rivaroxaban as a safe treatment option for these patients.

Therapy for hyperthermia-induced seizures in Scn1a mutant rats.

PURPOSE: Mutations in the SCN1A gene, which encodes the α1 subunit of voltage-gated sodium channels, cause generalized epilepsy with febrile seizures plus (GEFS+) and severe myoclonic epilepsy of infancy (SMEI). N1417H-Scn1a mutant rats are considered to be an animal model of human FS+ or GEFS+. To assess the pharmacologic validity of this model, we compared the efficacies of eight different antiepileptic drugs (AEDs) for the treatment of hyperthermia-induced seizures using N1417H-Scn1a mutant rats. METHODS: AEDs used in this study included valproate, carbamazepine (CBZ), phenobarbital, gabapentin, acetazolamide, diazepam (DZP), topiramate, and potassium bromide (KBr). The effects of these AEDs were evaluated using the hot water model, which is a model of experimental FS. Five-week-old rats were pretreated with each AED and immersed in water at 45°C to induce hyperthermia-induced seizures. The seizure manifestations and video-electroencephalographic recordings were evaluated. Furthermore, the effects of each AED on motor coordination and balance were assessed using the balance-beam test. KEY FINDINGS: KBr significantly reduced seizure durations, and its anticonvulsant effects were comparable to those of DZP. On the other hand, CBZ decreased the seizure threshold. In addition, DZP and not KBr showed significant impairment in motor coordination and balance. SIGNIFICANCE: DZP and KBr showed potent inhibitory effects against hyperthermia-induced seizures in the Scn1a mutant rats, whereas CBZ exhibited adverse effects. These responses to hyperthermia-induced seizures were similar to those in patients with GEFS+ and SMEI. N1417H-Scn1a mutant rats may, therefore, be useful for testing the efficacy of new AEDs against FS in GEFS+ and SMEI patients.

Empirical approach for improved estimation of unbound serum concentrations of valproic acid in epileptic infants by considering their physical development.

The unbound serum concentration of valproic acid (VPA) is closely related to its therapeutic efficacy. In epileptic infants, the unbound VPA concentration varies largely from patient to patient, being difficult to predict using the reported equations for older children. To establish an equation to estimate the unbound concentration in infants, we empirically characterized the relationship between total and unbound VPA concentrations, taking their growth and development into consideration. Data were retrospectively collected from archived clinical records of 30 epileptic infants aged 0-11 months old. The relationship between total and unbound VPA concentrations was analyzed according to the Langmuir equation, in which the patient's body weight, height, and body surface area were considered as physical development indices. Inter- and intra-individual variabilities in the VPA concentrations were also considered. It was shown that the unbound VPA concentration in infants is properly estimated when their body weights are taken into account, in which the parameter for the maximum binding site concentration (Bm) increases as the body weight increases, while that for the dissociation constant (Kd) is unaltered. Additionally, the relationship was shown to slightly change when the infants are concomitantly treated with VPA and the other antiepileptics. These findings provide useful information to adjust the VPA dosage to achieve optimal therapeutic efficacy in epileptic infants.

Impact of silicone oil tamponade on intravitreally injected vancomycin pharmacokinetics in cynomolgus monkey eyes.

Intravitreal injections of vancomycin (VCM) and ceftazidime (CAZ) are commonly used to treat infectious endophthalmitis. When patient cases require retinal detachment with silicone oil (SO) tamponade, the antibiotic doses are empirically reduced to 25 %. Currently, there is no scientific evidence for these empirical dose reductions. The purpose of the present study is to determine the quantitative impact that SO tamponades have on intraocular VCM pharmacokinetics. Because of high invasiveness of frequent sampling of intraocular VCM concentrations in human, this pharmacokinetic study was performed in cynomolgus monkey's eyes. Population pharmacokinetic modeling and simulation were performed using 75 different intraocular VCM concentrations obtained from 8 male cynomolgus monkeys. A one-compartment model with a first-order diffusion rate was used as a structural pharmacokinetic model. From the covariate analysis, SO tamponade significantly decreased the volume of distribution while pars plana vitrectomy with lensectomy (PPV) significantly increased the clearance and diffusion rate constants. From the Monte Carlo simulation (n = 1,000), the median time above minimum inhibitory concentration (T>MIC, a therapeutic effect index) durations of SO and normal eyes at clinical doses of 1,000 µg were 2.6 and 11.0 days, respectively. Using intravitreal injections of VCM with SO tamponade or PPV may reduce the therapeutic effect.

Urine volume to hydration volume ratio is associated with pharmacokinetics of high-dose methotrexate in patients with primary central nervous system lymphoma.

High-dose methotrexate (HD-MTX)-based chemotherapy is the first-line treatment for primary central nervous system lymphoma (PCNSL), but is associated with severe adverse effects, including myelosuppression and renal impairment. MTX is primarily excreted by the kidneys. Renal function calculated using serum creatinine (Scr) derived from muscle may be overestimated in elderly PCNSL patients. Therefore, we aimed to construct a population pharmacokinetic model in PCNSL patients and explore the factors associated with MTX clearance. Sixteen PCNSL patients (median age, 66 years) treated with HD-MTX were included, and serum MTX concentrations were measured at 193 points in 49 courses. A population pharmacokinetic analysis was performed using NONMEM. A Monte Carlo simulation was conducted, in which serum MTX concentrations were stratified into three groups of creatine clearance (Ccr) (50, 75, and 100 ml/min) with three groups of the urine volume to hydration volume (UV/HV) ratio (<1, 1-2, and >2). The final model was constructed as follows: MTX clearance = 4.90·(Ccr/94.5)0.456 ·(UV/HV)0.458 . In the Monte Carlo simulation, serum MTX concentrations were below the standard values (10, 1, and 0.1 µM at 24, 48, and 72 h, respectively, after the start of the MTX administration) in most patients with UV/HV >2, even with Ccr of 50 ml/min. Conversely, half of the patients with UV/HV <1 and Ccr of 50 ml/min failed to achieve the standard values. The present results demonstrated that the UV/HV ratio was useful for describing the pharmacokinetics of MTX in PCNSL patients.

Pharmacokinetics of Intravitreal Vancomycin and Ceftazidime in Silicone Oil-Filled Macaque Eyes.

Purpose: This study evaluated the pharmacokinetics of intravitreal vancomycin and ceftazidime in the aqueous humor of macaque eyes filled with silicone oil in the vitreous cavity. Methods: Intravitreal vancomycin (1 mg/0.1 mL) and ceftazidime (2 mg/0.1 mL) were injected into four normal macaque eyes, four vitrectomized aphakic macaque eyes, and four previously vitrectomized aphakic macaque eyes filled with silicone oil (silicone oil-filled eyes). Aqueous humor samples (0.1 mL) were obtained just before injection and at 2 and 5 hours and 1, 2, 3, 5, 7, and 10 days after injection. In each group, corneal endothelial cell density (ECD) measurements and electroretinogram (ERG) recordings were obtained before injection and after 1 month. Results: The half-lives of vancomycin in the aqueous humor of normal, vitrectomized, and silicone oil-filled eyes were 29.4, 21.1, and 6.8 hours, respectively, and those of ceftazidime were 20.4, 5.2, and 3.1 hours, respectively. The maximum vancomycin aqueous humor concentrations of normal, vitrectomized, and silicone oil-filled eyes were 151.4, 205.6, and 543.5 µg/mL, respectively, and the maximum ceftazidime aqueous humor concentrations are 64.6, 260.0, and 1176.3 µg/mL, respectively. There was no change in ECD, and ERG was not declined after intravitreal injection in all groups. Conclusions: The half-lives of vancomycin and ceftazidime in the aqueous humor were shorter in silicone oil-filled eyes than in normal and vitrectomized eyes. High antibiotic concentrations in silicone oil-filled eyes seemed to be well tolerated. Translational Relevance: This study aids in estimating how often an antibiotic should be intravitreally injected for endophthalmitis of silicone oil-filled eyes.

Genetic variants of alcohol-metabolizing enzymes in Brugada syndrome: Insights into syncope after drinking alcohol.

BACKGROUND: Patients with Brugada syndrome (BrS) are known to have arrhythmic events after alcohol drinking and are recommended to avoid its excessive intake. Mechanisms underlying the alcohol-induced cardiac events are however unknown. This study aimed to test the hypothesis whether activity of alcohol-metabolizing enzymes determines fatal arrhythmic events after drinking alcohol. METHODS: A total of 198 Japanese patients with BrS were enrolled in this study. These patients were classified into symptomatic (n = 90) and asymptomatic (n = 108) groups. The former was divided into an alcohol-related group (syncope after alcohol drinking, n = 16) and an alcohol-unrelated group (n = 74). Polymerase chain reaction was performed to determine genetic variants of genes encoding alcohol dehydrogenase 1B (ADH1B) and aldehyde dehydrogenase 2 (ALDH2). RESULTS: The genotype distribution for ALDH2 was not significantly different between symptomatic and asymptomatic groups and between alcohol-related and alcohol-unrelated groups. The genotype distribution for ADH1B was not significantly different between symptomatic and asymptomatic groups, but the genotype ADH1B His/His was significantly more prevalent in the alcohol-related group than in the alcohol-unrelated group (81.3% vs 50%, P = .023). In multivariate logistic regression analysis, the genotype of ADH1B His/His was independently associated with syncope after alcohol drinking (odds ratio, 5.746; 95% confidence interval, 1.580-28.421; P = .007). CONCLUSIONS: Arrhythmic events after alcohol drinking was associated with enhanced activity of alcohol-metabolizing enzyme ADH1B in our cohort of BrS. Therefore, the lifestyle change to avoid the excessive alcohol intake deserves attention.

Population Pharmacokinetics and Pharmacodynamics of Apixaban Linking Its Plasma Concentration to Intrinsic Activated Coagulation Factor X Activity in Japanese Patients with Atrial Fibrillation.

Apixaban is used in the prevention and treatment of patients with deep vein thrombosis or pulmonary embolism, and in the prevention of stroke or systemic embolism in patients with nonvalvular atrial fibrillation (AF). In this study, we aimed to elucidate intrinsic factors affecting efficacy of apixaban by conducting population pharmacokinetic and pharmacodynamic analysis using data from 81 Japanese AF patients. The intrinsic FXa activity was determined to assess the pharmacodynamic effect of apixaban. The pharmacokinetic and pharmacodynamic profiles were described based on a one-compartment model with first-order absorption and a maximum inhibitory model, respectively. Pharmacokinetic and pharmacodynamic analysis was conducted using a nonlinear mixed effect modeling program. The population pharmacokinetic parameters of apixaban were fixed at the reported values in our recent study. The population mean of half-maximal inhibitory concentration (IC50) of apixaban was estimated to be 45.3 ng/mL. The population mean IC50 decreased 27.7% for patients with heart failure, but increased 55% for patients with a medical history of cerebral infarction. In contrast, no covariates affected the population mean of baseline of intrinsic FXa activity (BASE) and maximum effect (Imax) value of apixaban. The population mean of BASE and Imax value were estimated to be 40.2 and 38.4 nmol/min/mg protein, respectively. The present study demonstrates for the first time that the co-morbidity of heart failure as well as the medical history of cerebral infarction are an intrinsic factor affecting the pharmacodynamics of apixaban.