Prediction of Corresponding Dose of Transdermal Blonanserin to Oral Dose Based on Dopamine D2 Receptor Occupancy: Unique Characteristics of Blonanserin Transdermal Patch.

BACKGROUND/PURPOSE: Blonanserin is an atypical antipsychotic, a potent selective antagonist of dopamine D2 receptor (D2), prescribed as oral formulations in patients with schizophrenia. Blonanserin transdermal patch was developed to provide a new treatment option, but the corresponding dose to oral blonanserin was not clear. The aims of this study were to clarify the pharmacokinetic (PK)-pharmacodynamic characteristics of blonanserin after transdermal patch application and to evaluate the corresponding dose to oral formulation based on striatal D2 occupancy. METHODS: The relationship between D2 occupancy and plasma blonanserin concentration was analyzed using an Emax model based on data from positron emission tomography study with oral and transdermal blonanserin. D2 occupancy was simulated using Emax models based on the observed plasma concentrations and the simulated plasma concentrations obtained from population PK model. RESULTS: Plasma blonanserin concentration levels after repeated patch applications were nearly stable throughout the day and no effect of sex, advanced age, or application site was detected. The concentration at half maximal D2 occupancy during transdermal patch applications, 0.857 ng/mL, was higher than that after oral doses, 0.112 ng/mL, suggesting metabolite contribution after oral doses. The median predicted D2 occupancy during blonanserin patch applications at doses of 40 and 80 mg/d was 48.7% and 62.5%, respectively, and the distribution of D2 occupancy at these doses could cover most of that at oral doses of 8 to 24 mg/d. CONCLUSIONS: Predicted D2 occupancy suggested that a 40- to 80-mg/d blonanserin transdermal patch dose corresponds to an 8- to 24-mg/d oral dose for the treatment of schizophrenia.

Imeglimin population pharmacokinetics and dose adjustment predictions for renal impairment in Japanese and Western patients with type 2 diabetes.

Imeglimin is an orally administered first-in-class drug to treat type 2 diabetes mellitus (T2DM) and is mainly excreted unchanged by the kidneys. The present study aimed to define the pharmacokinetic (PK) characteristics of imeglimin using population PK analysis and to determine the optimal dosing regimen for Japanese patients with T2DM and chronic kidney disease (CKD). Imeglimin plasma concentrations in Japanese and Western healthy volunteers, and patients with T2DM, including patients with mild to severe CKD with an estimated glomerular filtration rate (eGFR) greater than 14 ml/min/1.73 m2 were included in a population PK analysis. PK simulations were conducted using a population PK model, and the area under concentration-time curve (AUC) was extrapolated with power regression analysis to lower eGFR. The influence of eGFR, weight, and age on apparent clearance and of dose on relative bioavailability were quantified by population PK analysis. Simulations and extrapolation revealed that the recommended dosing regimen based on the AUC was 500 mg twice daily (b.i.d.) for patients with eGFR 15-45 ml/min/1.73 m2 , and 500 mg with a longer dosing interval was suggested for those with eGFR less than 15. Simulations revealed that differences in plasma AUCs between Japanese and Western patients at the same dose were mainly driven by a difference in the eGFR and that the plasma AUC after 1000 and 1500 mg b.i.d. in Japanese and Western patients, respectively, was comparable in the phase IIb studies. These results indicate suitable dosages of imeglimin in the clinical setting of T2DM with renal impairment.

Pharmacokinetic Evaluation of Blonanserin Transdermal Patch: Population Analysis and Simulation of Plasma Concentration and Dopamine D2 Receptor Occupancy in Clinical Settings.

Blonanserin is an atypical antipsychotic drug with high affinity and selective antagonism for dopamine D2 and D3 and serotonin 5-HT2A receptors. Blonanserin transdermal patch is the first transdermal formulation developed for the treatment of schizophrenia. The purpose of this population pharmacokinetic (PPK) analysis was to evaluate the characteristics of blonanserin pharmacokinetics after transdermal patch application, to estimate the daily fluctuation in blonanserin plasma concentration, and to evaluate the impact of patch application noncompliance to support usage in clinical settings. A total of 3747 plasma blonanserin concentrations from 9 clinical studies (93 healthy volunteers and 348 patients with schizophrenia) were used in the PPK analysis. The plasma concentration was predicted using the final PPK model, and dopamine D2 receptor occupancy was estimated on the basis of the results of a separately reported positron emission tomography study. A 2-compartment, parallel zero-order absorption with a lag time and first-order elimination model was developed to describe the pharmacokinetics of blonanserin, including the change in absorption rate during patch application. The maximum/minimum ratio of plasma concentration was estimated as 1.10 at steady state, indicating minimal fluctuation. In the case of failure to remove the previous patch or a missing application, the increase or decrease in plasma concentration and dopamine D2 receptor occupancy was <20%. These results indicated that the plasma blonanserin concentration and dopamine D2 receptor occupancy were stable after blonanserin transdermal patch application, which may lead to improved tolerability during the treatment of patients with schizophrenia.

Prediction methods of drug-drug interactions of non-oral CYP3A4 substrates based on clinical interaction data after oral administrations - Validation with midazolam, alfentanil, and verapamil after intravenous administration and prediction for blonanserin transdermal patch.

Drug-drug interactions (DDI) have been examined for various drugs for oral use, but less for non-oral applications. This study provides DDI prediction methods for non-orally administered CYP3A4 substrates based on clinical DDI data of oral dosages. Gut availability (Fg) and fraction contribution of CYP3A4 to hepatic intrinsic clearance (fmCYP3A4) were predicted by AUC ratio (AUCR) in oral DDI study with/without grapefruit juice, and alteration in intrinsic clearances with/without ketoconazole, respectively. AUCRs of non-orally administered CYP3A4 substrates with/without inhibitors or inducers were predicted with the estimated Fg, fmCYP3A4 and changes in liver CYP3A4 activities with inhibitors/inducers predicted using Simcyp library. DDIs of intravenously administered midazolam and alfentanil with CYP3A4 inhibitors/inducers could be predicted well by this method with predicted AUCRs within ±64% of observed values. Moreover, maximum DDIs with strong CYP3A4 inducers could be predicted by comparing hepatic clearance with hepatic blood flow, as hepatic blood flow indicates the possible maximum hepatic clearance after strong enzyme induction. Predicted AUCRs of midazolam, alfentanil and R- and S-verapamil were less than, but not far from observed ratios, suggesting good conservative prediction. These methods were applied to blonanserin transdermal patch, suggesting much smaller interaction with CYP3A4 inhibitors/inducers compared to oral dosage of blonanserin.

Cerebrospinal pharmacokinetic and pharmacodynamic analysis of efficacy of meropenem in paediatric patients with bacterial meningitis.

BACKGROUND: Meropenem is widely used for the treatment of paediatric patients with bacterial meningitis, but the pharmacodynamic (PD) basis for this has not been fully elucidated. OBJECTIVES: A cerebrospinal pharmacokinetic (PK) and PD analysis was performed to identify the optimal dosage regimen for paediatric patients with inflamed central nervous system disease (bacterial men-ingitis). PATIENTS AND METHODS: Paediatric data from three clinical studies were used to build a novel population PK model with a cerebrospinal fluid (CSF) compartment, assuming CSF clearance of 0.021 L/h from a physical-anatomical perspective. The bactericidal target attainment rates in CSF [50%T>MIC(CSF)], after various dosage regimens, were simulated on the basis of reported or observed minimum inhibitory concentration (MIC) distributions and a newly developed population PK model including CSF concentrations. The effects of increased dose and/or prolonged infusion on target attainment were investigated. RESULTS: Clinical data from 154 patients {mean age 30.6 [standard deviation (SD) 34.4] months, mean body weight 12.4 (SD 7.6) kg} were used for the population PK analysis. The flat profile of the CSF concentration-time curve and attainment of 50%T>MIC(CSF) did not change markedly when the duration of infusion was increased, whereas attainment of 50%T>MIC(CSF) was improved by increasing the dose from 20 to 40 mg/kg q8h for penicillin-resistant Streptococcus pneumoniae and Pseudomonas aeruginosa. Thirty-six patients who achieved satisfactory clinical cure showed at least 75.3%T>MIC(CSF). CONCLUSIONS: A high dose of meropenem (40 mg/kg q8h) is necessary to achieve clinical efficacy in paediatric patients with bacterial meningitis.

Pharmacokinetic evaluation of liposomal amphotericin B (L-AMB) in patients with invasive fungal infection: Population approach in Japanese pediatrics.

The pharmacokinetic characteristics of liposomal amphotericin B (L-AMB; AmBisome(®)) in patients with invasive fungal infection were investigated. A population pharmacokinetic (PK) model in Japanese pediatric patients was developed based on 159 serum amphotericin B (AMPH-B) concentrations obtained in a post-marketing clinical study. The subjects were 39 patients with a mean age of 8.4 years (SD 4.5) and mean body weight of 27.1 kg (SD 14.1). A two-compartment PK model with zero-order input and first-order elimination was fitted to serum AMPH-B concentrations for L-AMB doses of 1.0, 2.5, and 5.0 mg/kg/day. Body weight showed significant correlations with PK parameters, such as clearance (CL) and distribution volume of the central compartment (Vc). The predicted Cmax/dose and AUC0-24/dose in Japanese pediatric patients were similar to those in non-Japanese pediatric patients and Japanese adult patients. Extremely large increases in Ctrough compared with predicted values were observed in some Japanese pediatric patients, but no relationships with demographic characteristics, clinical laboratory test values, or representative adverse drug reaction (decreased potassium) were found. The population PK parameters in this study are useful for simulating PK profiles of L-AMB and will be helpful for PK exposure comparisons among different populations and in investigations of pharmacokinetic-pharmacodynamic characteristics in patients. CHEMICAL COMPOUNDS: Amphotericin B Deoxycholate (PubChem CID:23668620); amphotericin B (PubChem CID:5280965); 3-nitrophenol (PubChem CID:11137); methanol (PubChem CID:887).

Optimal treatment schedule of meropenem for adult patients with febrile neutropenia based on pharmacokinetic-pharmacodynamic analysis.

The objectives of this study were to develop a population pharmacokinetic (PK) model of meropenem, to simulate the percent time above minimum inhibitory concentration (%T > MIC) at various MICs, and to estimate effective dosage regimens by calculating the target attainment rates against various strains of bacteria. A total of 209 plasma samples (1-3 concentrations per patient) were obtained from 98 adult Japanese patients with febrile neutropenia in an open-labeled Phase 3 study. The final population PK model was fit to a two-compartment model with zero-order input. Creatinine clearance had a positive significant correlation with CL. Gender had a significant effect on Vc; however, this effect was small, and the PK profile in male patients was similar to that in female patients. The population PK parameters developed in this study are useful in simulating PK profiles of meropenem at various dosage regimens precisely for calculation of %T > MIC. The PK-PD analysis indicated that 0.5 g every 6 h (q6h) was more effective than 1 g q12h, although provided 2 g per day in total. A meropenem dosage regimen of 1 g q8h and/or longer infusion duration was better against a pathogen of comparatively low sensitivity, Pseudomonas aeruginosa (for MIC ≥2 µg/ml). Although causative bacteria were identified in a small number of patients, the target attainment rates at 75%T > MIC (89%) were comparable to microbiological response (89%). The present PK-PD analyses under various conditions are useful in the treatment of febrile neutropenia.

Optimal dosage regimen of meropenem for pediatric patients based on pharmacokinetic/pharmacodynamic considerations.

A population pharmacokinetic (PK) model for meropenem in Japanese pediatric patients with various infectious diseases was developed based on 116 plasma concentrations from 50 pediatric patients. The population PK parameters developed in this analysis are useful for calculation of the percent time above minimum inhibitory concentration (%T>MIC) and for optimal dosing of meropenem in pediatric patients. After dosing at 20 mg/kg t.i.d. by 0.5-h infusion (approved standard dose for pediatric patients in Japan), the target value of 50%T>MIC was achieved, indicating that 20 mg/kg t.i.d. by 0.5-h infusion is effective for susceptible bacteria. In contrast, for bacteria with higher MICs such as Pseudomonas aeruginosa (MIC ≥ 2 µg/mL), the probability of target attainment of 50%T>MIC was 60.7% at a dose of 40 mg/kg t.i.d. by 0.5-h infusion (highest dose approved for pediatric patients in Japan). The simulations described in this article indicated that 40 mg/kg t.i.d. with a longer infusion duration (e.g., 4 h) is more effective against bacteria with a MIC higher than 2 µg/mL. The predicted probability of target attainment for 50%T>MIC (97.0%) was well correlated not only to the microbiological efficacy rate (97.0%) but also to the clinical efficacy rate (95.9%) in the present phase 3 study.

Pharmacokinetics of beclomethasone dipropionate in an hydrofluoroalkane-134a propellant system in Japanese children with bronchial asthma.

BACKGROUND: Hydrofluoroalkane-134a (HFA) has been shown to be a safe replacement for chlorofluorocarbons (CFCs) as a pharmaceutical propellant, with the advantage that it has no ozone-depleting potential. This is the first report of the pharmacokinetics of beclomethasone dipropionate (BDP) delivered from a pressurized solution formulation using an HFA propellant system (HFA-BDP) in Japanese children with bronchial asthma. METHODS: Plasma concentrations of beclomethasone 17-monopropionate (17-BMP),a major metabolite of BDP, following an inhaled dose of HFA-BDP (200 microg as four inhalations from 50 microg/actuation) in five Japanese children with bronchial asthma were quantified and analyzed by a non-compartmental analysis to obtain pharmacokinetic parameters. RESULTS: The area under the concentration-time curve from time zero to the last quantifiable time (AUC(0-t)) was 1659 +/- 850 pg x h/mL (arithmetic mean +/- standard deviation (SD)), the maximum concentration observed (C(max)) was 825 +/- 453 pg/mL and the apparent elimination half-life (t(1/2)) was 2.1 +/- 0.7 hours. The time to reach Cmax Tmax was 0.5 hours in all patients. No special relationship was observed between these parameters and age or body weight. These parameters were compared with the previously reported parameters of American children with bronchial asthma. The Japanese/American ratio of the geometric means of each parameter was 1.36 for AUC(0-t), 1.04 for Cmax and 1.4 for t(1/2). The median of Tmax was 0.5 hours in American patients as well as Japanese patients. CONCLUSIONS: The pharmacokinetics of HFA-BDP in Japanese children with bronchial asthma are reported for the first time and a similarity to those in American children is suggested.