Igarashi, Yuki

写真a

Affiliation

Faculty of Pharmacy, Department of Pharmacy Division of Pharmacodynamics (Shiba-Kyoritsu)

Position

Research Associate/Assistant Professor/Instructor
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Profile Summary 【 Display / hide 】

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Career 【 Display / hide 】

  • 2023.04
    -
    2025.03

    医療法人社団　緑成会横浜総合病院, 薬剤部

  • 2025.04
    -
    Present

    慶應義塾大学, 薬学部　薬効解析学講座, 助教

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Academic Background 【 Display / hide 】

  • 2019.04
    -
    2023.03

    慶應義塾大学大学院

    Graduate School, Graduated, Doctoral course

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Academic Degrees 【 Display / hide 】

  • 博士（薬学）, 慶應義塾大学大学院, Coursework, 2023.03

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Licenses and Qualifications 【 Display / hide 】

  • 薬剤師免許, 2019.05

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Papers 【 Display / hide 】

  • External validation of a flowchart related to achieving the target area under the concentration-time curve for vancomycin: A retrospective multicenter study.

    Tomoyuki Ishigo, Ayako Suzuki, Yuta Ibe, Satoshi Fujii, Masahide Fukudo, Hiroaki Yoshida, Hiroaki Tanaka, Hisato Fujihara, Fumihiro Yamaguchi, Fumiya Ebihara, Takumi Maruyama, Yusuke Yagi, Yukihiro Hamada, Masaru Samura, Fumio Nagumo, Toshiaki Komatsu, Atsushi Tomizawa, Akitoshi Takuma, Hiroaki Chiba, Yoshifumi Nishi, Yuki Igarashi, Yuki Enoki, Kazuaki Matsumoto

    Journal of Infection and Chemotherapy 31 ( 5 )  2025.05

    Accepted,  ISSN  1341321X

    　View Summary

    During therapeutic drug monitoring (TDM) for vancomycin (VCM), the area under the concentration-time curve (AUC) is important for balancing efficacy versus toxicity. In a previous study, we developed a decision tree (DT) model to achieve the target AUC during TDM over the follow-up period (AUCfollow-up). This study aimed to validate the DT model for achieving the target AUCfollow-up. Patients who received VCM for at least 72 h and had an initial TDM within four doses between January 2023 and December 2023 were analyzed. The AUC of the initial TDM was calculated over 2-point (peak/trough) concentrations via Bayesian estimation. The target AUCfollow-up was defined as 400–600 μg h/mL. Among 188 patients (median age [interquartile range], 66 [56, 79] years; 50 % female), the target AUCfollow-up was achieved in 70 % (132/188). When the predicted AUC was 400–600 μg h/mL, 84 % (102/121) achieved the target AUCfollow-up. In a 12 h dosing interval subgroup, 86 % (88/102) achieved the target AUCfollow-up. Conversely, when the predicted AUC was <400 or >600 μg h/mL, the proportion who achieved the target AUCfollow-up dropped to 44 % (30/67). Only 30 % (3/10) of those with creatinine clearance rates of >130 mL/min/1.73 m2 achieved the target. The area under the receiver operating characteristics curve was 0.74, and the R2 value was 0.15. Our findings confirmed the external validity of the DT model and supported its use for optimizing VCM dosing. Overall, the DT model offers a reliable framework for achieving target AUC values during follow-up for TDM, aiding safe and effective treatment.

  • Influence factors of metronidazole-related CNS disorders: an analysis of the Japan adverse drug event report and FDA adverse event reporting system

    Takada K., Enoki Y., Samura M., Igarashi Y., Taguchi K., Tanikawa K., Matsumoto K.

    Expert Opinion on Drug Safety  2025.04

    Research paper (scientific journal), Accepted,  ISSN  14740338

    　View Summary

    Background: Metronidazole (MNZ) can be administered for various infections. The impact of comorbidities/concomitant drugs on MNZ-induced central nervous system (CNS) disorders remains unclear. Research design and methods: We assessed the risk of metronidazole-related CNS disorders using the Japan Adverse Drug Event Report (JADER, May 2023) and the US Food and Drug Administration Adverse Event Reporting System (FAERS, Q1 2023), excluding comorbidities/concomitant drugs. Clonazepam and diazepam were evaluated as potential prophylactics based on the efficacy of benzodiazepines for MNZ-related CNS disorders. Reporting odds ratios (ROR) and 95% confidence intervals (CI) were calculated. Additionally, sensitivity analysis by sex and age was conducted. Results: The ROR (95% CI) of CNS disorders associated with MNZ in JADER and FAERS were 3.16 (2.69–3.72) and 1.69 (1.64–1.73), respectively. MNZ was significantly related to CNS disorders after excluding comorbidities (brain/spinal cord or liver abscesses) and concomitant drugs (glucocorticoids, antiepileptic, antiparkinson, and schizophrenia drugs). In sensitivity analysis, MNZ was significantly related to CNS disorders, despite sex and age. The ROR in the concomitant with clonazepam (CZP) was 0.70 (0.53–0.92) in FAERS. Conclusion: MNZ may be associated with CNS disorders, even if comorbidities/concomitant drugs that are potential risk factors for CNS disorders are excluded. Additionally, CZP may suppress CNS disorders.

  • Development and validation of a population pharmacokinetic model of vancomycin for patients of advanced age

    Takada K., Samura M., Igarashi Y., Suzuki A., Ishigo T., Fujii S., Ibe Y., Yoshida H., Tanaka H., Ebihara F., Maruyama T., Hamada Y., Komatsu T., Tomizawa A., Takuma A., Chiba H., Yagi Y., Nishi Y., Enoki Y., Taguchi K., Tanikawa K., Kunishima H., Matsumoto K.

    Journal of Pharmaceutical Health Care and Sciences 11 ( 1 )  2025.03

    Accepted

    　View Summary

    Background: Population pharmacokinetic (PPK) models of vancomycin (VCM) commonly use creatinine clearance (CLcr) as a covariate for clearance (CL). However, relying on CLcr in patients of advanced age may lead to inaccuracies in estimating VCM clearance. Therefore, this study aimed to develop and validate a new PPK model specifically for patients aged 75 years and older. Methods: PPK analysis was performed based on the blood concentrations of VCM (n = 159 patients). The predictive performance of the developed model was compared with that of previous models using mean absolute error (MAE) and mean squared error (MSE) for another dataset. Results: The PPK analysis optimized a two-compartment model using CLcr and the Alb levels as covariates at the central compartment of VCM clearance. The final model was as follows: CL (L/h) = 1.96 × (CLcr/3.09) 0.63 × (Serum albumin (Alb) /2.3) 0.22 × exponential (0.11). Clearance between the central and peripheral compartments (L/h) = 4.86. Central compartment volume of distribution (L) = 31.78. Peripheral compartment volume of distribution (L) = 53.64. The validation study revealed that compared with those of previous models (ranging from 0.67 to 0.79 L/h and from 0.81 to 1.11 (L/h)2, respectively), the final model demonstrated the smallest MAE of 0.60 L/h and MSE of 0.65 (L/h)2 for patients of advanced age with serum creatinine levels of < 0.6 mg/dL. Conclusion: The PPK model of VCM for patients of advanced age was optimized by adding the Alb levels and CLcr as covariates for CL. The predictive accuracy of the PPK model for patients with an SCr of < 0.6 mg/dL tended to be higher than those of previous models based just on CLcr. Thus, dosage is suggested to be adjusted based on CLcr and Alb levels for patients with an SCr of < 0.6 mg/dL.

  • SARS-CoV-2 mRNA vaccine-related myocarditis and pericarditis: An analysis of the Japanese Adverse Drug Event Report database.

    Keisuke Takada, Kazuaki Taguchi, Masaru Samura, Yuki Igarashi, Yuko Okamoto, Yuki Enoki, Koji Tanikawa, Kazuaki Matsumoto

    Journal of Infection and Chemotherapy 31 ( 1 )  2025.01

    Accepted

  • Simulated achievement rate of β-lactams/nacubactam treatment in humans using instantaneous MIC-based PK/PD analysis.

    Yuki Igarashi, Kazuaki Taguchi, Yuki Enoki, Victor Tuan Giam Chuang, Kazuaki Matsumoto

    Journal of Antimicrobial Chemotherapy 80 ( 2 ) 547 - 553 2024.12

    Lead author, Accepted,  ISSN  03057453

    　View Summary

    Background: Nacubactam (NAC), a new diazabicyclooctane β-lactamase inhibitor, is being developed for use together with aztreonam (AZT) and cefepime (CFPM). However, the effective clinical dosages of AZT/NAC and CFPM/NAC have not yet been established. We have previously shown that free time above instantaneous MIC (fT > MICi) is a valuable pharmacokinetic (PK)/pharmacodynamic parameter for β-lactam (BL)/NAC in a mouse thigh infection model. Objectives: This study simulated the fT > MICi (%) for AZT/NAC and CFPM/NAC against carbapenemase-producing Enterobacterales (CPE) with different MIC in humans to estimate the clinical efficacy at practically achievable combination doses of AZT/NAC and CFPM/NAC. Methods: Using previously reported PK parameters of each drug in humans and chequerboard MIC data, we calculated the fT > MICi (%) for AZT/NAC and CFPM/NAC in 10 000 simulated patients to predict the percentages of target attainment of bacteriostatic and bactericidal efficacies at various combined doses. Results: The results predicted that both BL/NAC combinations could achieve 100% 2 log10-kill against CPE strains at the lowest combination dose (0.5 g/0.5 g q8h). Additionally, in MIC studies examining BLs/NAC at a 1:1 ratio, the dosage regimen for strains with MICcomb ≤ 1 mg/L was expected to offer 100% bactericidal efficacy (2 log10-kill) at 0.5 g/0.5 g q8h or higher doses. For strains with 1 mg/L < MICcomb ≤ 16 mg/L, BLs/NAC at a 2 g/2 g q8h was predicted to produce bactericidal efficacy (1 log10-kill). At MICcomb = 32 mg/L, some bacteriostatic effect was expected at high BL doses. Conclusions: AZT/NAC and CFPM/NAC are bactericidal against CPE at practically achievable dosages.

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Presentations 【 Display / hide 】

  • β-ラクタム薬/β-ラクタマーゼ阻害薬の併用療法における in vivo pharmacokinetics/pharmacodynamics評価方法の構築

    五十嵐裕貴

    第73回日本化学療法学会総会 (神奈川県) , 

    2025.05
    , 

    Poster presentation

  • 免疫抑制マウス肺部S. pneumoniae感染モデルを用いたcefditoren pivoxilのPK/PD解析及び臨床用量評価

    五十嵐裕貴，小島菜奈，髙田啓介，榎木裕紀，田口和明，谷川浩司，松元一明

    第34回日本医療薬学会年会 (千葉県) , 

    2024.11
    , 

    Oral presentation (general)

  • 免疫抑制マウス肺部S. pneumoniae感染モデルを用いたcefditoren pivoxilのPK/PD解析及び臨床用量評価

    五十嵐裕貴，小島菜奈，髙田啓介，榎木裕紀，田口和明，谷川浩司，松元一明

    第34回日本医療薬学会年会 (千葉県) , 

    2024.11
    , 

    Oral presentation (general)

  • テジゾリドのマウスMRSA骨髄炎モデル用いたPK/PD評価

    劉小茜，田代渉，五十嵐裕貴，竹村渉，榎木裕紀，田口和明，松元 一明

    MRSAフォーラム2022 (長崎県) , 

    2022.07
    , 

    Oral presentation (general)

  • テジゾリドのマウスMRSA骨髄炎モデル用いたPK/PD評価

    劉小茜，田代渉，五十嵐裕貴，竹村渉，榎木裕紀，田口和明，松元 一明

    MRSAフォーラム2022 (長崎県) , 

    2022.07
    , 

    Oral presentation (general)

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Awards 【 Display / hide 】

  • 日本化学療法学会Young Challenger Award（YCA）2025

    2025.05, 日本化学療法学会, β-ラクタム薬/β-ラクタマーゼ阻害薬の併用療法におけるin vivo pharmacokinetics/pharmacodynamics評価方法の構築

    Type of Award： Award from Japanese society, conference, symposium, etc.

  • 第34回日本医療薬学会年会Postdoctoral award

    2024.11, 日本医療薬学会, β-ラクタム薬/β-ラクタマーゼ阻害薬の併用療法におけるin vivo pharmacokinetics/pharmacodynamics評価方法の構築

    Type of Award： Award from Japanese society, conference, symposium, etc.

  • 2023年度KP会星野尚美記念薬学研究・活動奨励賞 研究論文部門

    2024, Development of an optimized and practical pharmacokinetics/pharmacodynamics analysis method for aztreonam/nacubactam against carbapenemase-producing K. pneumoniae

    Type of Award： Other

  • Sato Pharmaceutical Research Encouragement Award

    2020, 佐藤製薬株式会社, PK/PD理論に基づくCefditorenの適正使用を目指したマウスにおける薬物動態研究

    Type of Award： Other

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Courses Taught 【 Display / hide 】

  • STUDY OF MAJOR FIELD (PHARMACODYNAMICS)

    2025

  • SEMINAR (PHARMACODYNAMICS)

    2025

  • RESEARCH FOR BACHELOR'S THESIS 1

    2025

  • PRE-CLINICAL TRAINING FOR HOSPITAL & COMMUNITY PHARMACY

    2025

  • PHARMACEUTICAL-ENGLISH SEMINAR

    2025

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Memberships in Academic Societies 【 Display / hide 】

  • 日本臨床薬理学会, 

    2024.12
    -
    Present

  • 日本医療薬学会, 

    2021.08
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    Present

  • 日本化学療法学会, 

    2019.11
    -
    Present
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