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Dive into the research topics where Keisou Masuhara is active.

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Featured researches published by Keisou Masuhara.


Cancer Chemotherapy and Pharmacology | 1996

Relationship between pharmacokinetics of unchanged cisplatin and nephrotoxicity after intravenous infusions of cisplatin to cancer patients

Naomi Nagai; Masafumi Kinoshita; Hiroyasu Ogata; Daijiro Tsujino; Yuji Wada; Kazuhiko Someya; Tetsuro Ohno; Keisou Masuhara; Yoshio Tanaka; Katsuhiko Kato; Haruki Nagai; Akira Yokoyama; Yuzou Kurita

Abstract Purpose: The relationships between pharmacokinetic parameters of unchanged cisplatin (CDDP) and several markers for nephrotoxicity after CDDP infusion (80 mg/m2) over 2 and 4 h were quantitated in patients with various cancers (lung, stomach and colon cancers and mediastinal tumor). Methods: Plasma and urinary levels of unchanged CDDP were measured using a specific high-performance liquid chromatography method. Pharmacokinetic parameters were calculated according to the model-independent method. The nephrotoxicity markers, blood urea nitrogen (BUN), serum creatinine (SCr), plasma and urinary β2-microglobulin (BMGp and BMGu), urinary N-acetyl-β-D-glucosaminidase (NAG) and creatinine clearance (CCR) were monitored for 30 days following CDDP administration. Results: The maximum plasma concentration (Cmax), maximum urinary excretion rate (dAe/dtmax), area under the plasma concentration-time curve from time zero to infinity (AUC), cumulative amount excreted in urine from time zero to infinity (Ae), total clearance (Clt), renal clearance (Clr) and plasma half-life (t1/2) of unchanged CDDP were not significantly different between the 2-h and 4-h infusion schedules. The values of the nephrotoxicity markers changed significantly following CDDP administration, suggesting that CDDP chemotherapy (80 mg/m2) caused nephrotoxicity. The Cmax of unchanged CDDP was the most informative pharmacokinetic parameter for nephrotoxicity. Cmax was related to maximum BUN, maximum SCr and minimum CCR levels in 27 CDDP treatments according to an exponential model. Conclusion: In order to attain more effective CDDP chemotherapy with minimum nephrotoxicity, the present pharmacokinetic and pharmacodynamic studies suggest that the Cmax or steady-state plasma level of unchanged CDDP should be maintained between 1.5 and 2 μg/ml in a standard continuous infusion schedule over 2 h and 4 h.


The Journal of Clinical Pharmacology | 1998

Population Pharmacokinetics and Pharmacodynamics of Cisplatin in Patients with Cancer: Analysis with the NONMEM Program

Naomi Nagai; Hiroyasu Ogata; Yuji Wada; Daijiro Tsujino; Kazuhiko Someya; Tetsuro Ohno; Keisou Masuhara; Yoshio Tanaka; Haruki Takahashi; Haruki Nagai; Katsuhiko Kato; Yoichi Koshiba; Tamotsu Igarashi; Akira Yokoyama; Koichi Kinameri; Toshiyuki Kato; Yuzou Kurita

The population pharmacokinetics and pharmacodynamics of cisplatin (CDDP) were evaluated based on a mixed‐effect model using the NONMEM program. Unchanged CDDP in plasma was measured as a biologically active platinum species during CDDP chemotherapy, using high‐performance liquid chromatography. Plasma concentration measurements (157) of unchanged CDDP from 26 patients with cancer receiving 80 mg/m2 CDDP by infusion over 2 hours, 3.5 hours, or 4 hours were analyzed according to a one‐compartment model. The influences of individual characteristics such as body weight, dose schedule, course, and clinical laboratory values (renal function markers, albumin) on total body clearance (Cl) and volume of distribution (Vd) were examined. In the final pharmacokinetic model, body surface area and dose schedule affected Cl of unchanged CDDP. The Cl of CDDP was increased by 27.3% after the 2‐hour infusion schedule compared with Cl after the longer infusions. The Vd was estimated as 13.4 L/m2. The interindividual variability for Cl and Vd and residual variability were 22.9%, 30.9%, and 35.5%, respectively. The relationships between maximum concentration (Cmax) of unchanged CDDP and maximum blood urea nitrogen (BUNmax), or minimum creatinine clearance (ClCr,min) over a 1‐month period after CDDP administration were evaluated according to linear, exponential, or maximum response (Emax) models. The linear or Emax model described pharmacodynamics most successfully, with relatively large interindividual variability for both slope and EC50 (more than 25%). Residual variability was 15.3% and 17.1% in BUNmax and ClCrmin, respectively. The population means and interindividual and residual variability of pharmacokinetics and pharmacodynamics of CDDP were evaluated using the NONMEM program. The results of this study show that the population pharmacokinetic and pharmacodynamic approach could be useful to manage CDDP nephrotoxicity using sparse data in a clinical setting.


Pharmacotherapy | 2005

More Stable and Reliable Pharmacokinetics with Preprandial Administration of Cyclosporine Compared with Postprandial Administration in Patients with Refractory Nephrotic Syndrome

Tetsuro Kusaba; Yusuke Konno; Shigeo Hatta; Tomoya Fujino; Takashi Yasuda; Hiroshi Miura; Hiroyo Sasaki; Jun Okabayashi; Mei Murao; Tsutomu Sakurada; Goro Imai; Sayuri Shirai; Shingo Kuboshima; Yoshinori Shima; Goichi Ogimoto; Takeo Sato; Keisou Masuhara; Kenjiro Kimura

Study Objective. To compare the absorption profile of cyclosporine after preprandial administration with that after postprandial administration, and to determine which administration time resulted in a more stable absorption profile and the timing of the drug concentration that was the most reliable marker for monitoring drug absorption.


The Journal of Clinical Pharmacology | 2006

Population pharmacokinetic and pharmacodynamic analysis of a class IC antiarrhythmic, pilsicainide, in patients with cardiac arrhythmias.

Ryuichi Ogawa; Ryoji Kishi; Kiyoshi Mihara; Harumi Takahashi; Akihiko Takagi; Naoki Matsumoto; Keisou Masuhara; Kiyoshi Nakazawa; Fumihiko Miyake; Shinichi Kobayashi; Hirotoshi Echizen

Population pharmacokinetics (PK) of a sodium channel—blocking antiarrhythmic, pilsicainide, was studied using the nonlinear mixed‐effects modeling technique in 91 patients with cardiac arrhythmias (80 suspected Brugada syndrome [BrS] and 11 with atrial fibrillation) who received an intravenous infusion of 10 mg of the drug. Population pharmacodynamic (PD) analysis was also performed using an effect compartment model. PD responses were assessed by changes in electrocardiogram (ECG) pattern (BrS‐like elevation of ST‐segment) and conduction parameters. The final PK model showed that gender (values were 50% lower in women than in men) and creatinine clearance were significant (P < .01) covariates of weight‐normalized systemic clearance of pilsicainide. Patients who showed a BrS‐like ECG pattern after the drug administration also showed a significantly (P < .01) greater prolongation in His‐Purkinje conduction compared to the remaining patients. In conclusion, female gender, renal dysfunction, and the drug‐induced BrS‐like ECG morphology may be associated with augmented ECG responses to pilsicainide.


Journal of Chromatography B: Biomedical Sciences and Applications | 1990

High-performance liquid chromatographic analysis of unchanged cis-diamminedichloroplatinum (cisplatin) in plasma and urine with post-column derivatization

Masafumi Kinoshita; Naomi Yoshimura; Hiroyasu Ogata; Daijiro Tsujino; Toshiaki Takahashi; Satoru Takahashi; Yuji Wada; Kazuhiko Someya; Tetsuro Ohno; Keisou Masuhara; Yoshio Tanaka


Clinical and Experimental Nephrology | 2009

Preprandial microemulsion cyclosporine administration is effective for patients with refractory nephrotic syndrome

Sayuri Shirai; Takashi Yasuda; Hiroki Tsuchida; Shingo Kuboshima; Yusuke Konno; Yoshinori Shima; Takeo Sato; Shigeo Hatta; Keisou Masuhara; Kenjirou Kimura


Yakugaku Zasshi-journal of The Pharmaceutical Society of Japan | 2005

Impairment state of cognitive performance and the affecting factors in outpatients following gastrointestinal endoscopy after single-dose diazepam.

Kenichi Nakazono; Yoshiyuki Watanabe; Shinichi Nakaya; Yoshie Asami; Keisou Masuhara; Fumio Itoh; Hiroyasu Ogata


日本臨床生理学会雑誌 = Japanese journal of applied physiology | 2008

Drug Compliance in Cardiology Outpatients

Masatoshi Hara; Yuko Tohyo; Hidehiko Atsuta; Fumihiko Miyake; Nobuyoshi Narita; Keito Torikai; Takahide Matsuda; Yumiko Shimozato; Ikkou Sakaue; Keisou Masuhara; Satoshi Imamura


Japanese Circulation Journal-english Edition | 2003

Electrophysiological Characteristics in Brugada Syndrome-Like ST Elevation Induced by Pilsicainide Administration

Ryuichi Ogawa; Kiyoshi Nakazawa; Ryoji Kishi; Akihiko Takagi; Naoki Matsumoto; Keisou Masuhara; Fumihiko Miyake; Shinichi Kobayashi; Hirotoshi Echizen


Japanese Circulation Journal-english Edition | 2003

Predictability of the Na Channel Blockade Induced Brugada Syndrome-Like Electrocardiogram Using Genotype Screening in the SCN5A Gene

Ryuichi Ogawa; Kiyoshi Nakazawa; Ryoji Kishi; Akihiko Takagi; Naoki Matsumoto; Keisou Masuhara; Fumihiko Miyake; Shinichi Kobayashi; Hirotoshi Echizen

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Fumihiko Miyake

St. Marianna University School of Medicine

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Akihiko Takagi

St. Marianna University School of Medicine

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Hirotoshi Echizen

Meiji Pharmaceutical University

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Hiroyasu Ogata

Meiji Pharmaceutical University

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Kiyoshi Nakazawa

St. Marianna University School of Medicine

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Naoki Matsumoto

St. Marianna University School of Medicine

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Ryoji Kishi

St. Marianna University School of Medicine

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Ryuichi Ogawa

Meiji Pharmaceutical University

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Shinichi Kobayashi

St. Marianna University School of Medicine

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Yoshio Tanaka

St. Marianna University School of Medicine

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