Iatrogenic Cushing Syndrome from Interaction Between Ritonavir and Oral Budesonide During Direct Acting Antiviral Hepatitis C Therapy.

Direct acting antiviral (DAA) regimens containing ritonavir have been developed to treat hepatitis C, with fewer side effects than that by interferon-based regimens. However prescribers must be aware of drug-drug interactions. There are multiple reports of iatrogenic Cushing syndrome (CS) caused by ritonavir, when used to treat human immunodeficiency virus, increasing the bioavailability of exogenous steroids by inhibiting cytochrome p450 enzymes in the liver and gut wall and thus reducing steroid metabolism. We herein report a novel scenario of CS due to interaction between ritonavir for hepatitis C treatment and oral budesonide for autoimmune hepatitis.