Impact of body mass index and serum albumin levels on isavuconazole plasma concentrations in patients with haematological malignancies

Objectives The aim of this study was to investigate the fluctuations in isavuconazole concentrations and to identify influencing factors in Chinese patients with haematological malignancies. Methods A retrospective analysis was conducted on patients with haematological malignancies who received their first standard dose of isavuconazole treatment in 2024. Statistical analysis of trough concentrations of isavuconazole, demographics and clinical characteristics over 60 days of treatment was performed. A nomogram was constructed based on independent risk factors to predict isavuconazole trough concentrations > 7 mg/L. Results A total of 63 patients with a median age of 54 (39–63) years and 390 isavuconazole plasma concentrations with a median value of 5.68 mg/L (range 1.24–16.49 mg/L) were included. The median intra- and inter-individual coefficients of variation were 15.0% and 43.3%, respectively. In univariate and multivariate analysis, isavuconazole levels > 7 mg/L on day 7 were significantly associated with body mass index (BMI) and albumin (ALB). Compared to patients with a BMI > 21.0 kg/m2, those with a BMI ≤ 21.0 kg/m2 exhibited a 15.88-fold increased risk of isavuconazole trough concentrations > 7 mg/L. Similarly, patients with ALB ≥ 36.4 g/L showed a 4.71-fold higher risk of elevated isavuconazole levels than those with ALB < 36.4 g/L. A nomogram model for effectively predicting the risk of isavuconazole concentrations exceeding 7 mg/L based on BMI and ALB results was successfully established. Conclusions Patients with haematological malignancies treated with isavuconazole show modest plasma concentration variability. However, for patients with a BMI ≤ 21.0 kg/m2 and/or an ALB ≥ 36.4 g/L, we propose that therapeutic drug monitoring may assist in ensuring medication safety. Additionally, for the first time, a nomogram was developed to predict isavuconazole levels > 7 mg/L using BMI and ALB, though further validation is warranted.