Liver Necrosis in a Patient Receiving Isavuconazole: Making the Case for Therapeutic Drug Monitoring

An 81-year-old man prescribed isavuconazole for pulmonary fungal infection developed high serum transaminase levels and biopsy-confirmed hepatic necrosis associated with prolonged high serum isavuconazole levels. Genotyping revealed poor CYP3A5 activity/normal CYP3A4 activity. Older age and slow isavuconazole elimination likely led to isavuconazole-associated hepatic toxicity. This case underscores the importance of isavuconazole therapeutic drug monitoring.