Therapeutic Drug Monitoring of Isavuconazole: Lessons Learnt from a Real-life Setting in a Tertiary Care Center in India

INTRODUCTION: Isavuconazole is an emerging therapeutic option for invasive infections caused by molds, especially aspergillosis and mucormycosis. Isavuconazole has predictable pharmacokinetics and good bioavailability. These attributes have led to some doubts regarding the need for therapeutic drug monitoring (TDM). There are no data from India regarding TDM for isavuconazole. METHODS: A retrospective analysis of 50 patients who received oral isavuconazole for therapeutic purposes. Plasma isavuconazole levels were measured using a reversed phase high-performance liquid chromatography (HPLC) and UV detector with acetonitrile (ACN) as protein precipitating solvent. RESULTS: Of the 50 cases, 5 (10.0%) patients had subtherapeutic levels, while 45 (90.0%) had therapeutic levels. Higher body weight and solid organ transplantation (SOT) were significantly associated with subtherapeutic levels of isavuconazole (p-value < 0.05 for all). Receipt of a SOT was the only independent and statistically significant factor which was associated with subtherapeutic levels of isavuconazole (p-value < 0.05). CONCLUSION: Our study reemphasizes the need of TDM for isavuconazole and adds to the growing evidence for the need to obtain drug levels. Factors associated with subtherapeutic levels of isavuconazole need to be assessed in larger studies to help identify those patients who are at risk of having subtherapeutic drug levels. HOW TO CITE THIS ARTICLE: Prayag PS, Soman RN, Panchakshari SP, Ajapuje PS, Mahale NP, Dhupad S, et al. Therapeutic Drug Monitoring of Isavuconazole: Lessons Learnt from a Real-life Setting in a Tertiary Care Center in India. Indian J Crit Care Med 2023;27(4):260–264.