Cushing syndrome and tertiary adrenal insufficiency from prolonged concomitant use of budesonide and posaconazole

Budesonide is a 'non-absorbable' corticosteroid often used for gut graft versus host disease. Systemic exposure is usually minimal because of metabolism by cytochrome (CYP) 3A4 in enterocytes and the liver. However, concomitant use of posaconazole and voriconazole, inhibitors of CYP3A4 commonly used as antifungal prophylaxis in allograft patients receiving immunosuppression, can lead to substantial systemic steroid exposure. This paper describes a case of severe iatrogenic Cushing syndrome and tertiary adrenal insufficiency because of this interaction, highlighting the necessity for improved awareness of this phenomenon.