The hidden dangers of drug–drug interactions

Antiretroviral medications have the potential to produce serious drug interactions by interfering with the hepatic cytochrome P450 cascade. Ritonavir, a protease inhibitor, is a known CYP450 inhibitor that is commonly used in the treatment of HIV infection. Iatrogenic Cushing’s syndrome is caused by exposure to glucocorticoids and may be promoted by interaction with additional drugs that result in hypothalamic-pituitary-adrenal axis suppression. It is well documented in HIV-infected patients receiving inhaled steroids in combination with a ritonavir-containing antiretroviral regimen. This case describes a 45-year-old man with HIV who suffered an unintentional severe reaction between his HIV treatment and fluticasone while participating in an asthma research trial. He presented with classical Cushing’s features, as well as a decline in his respiratory health. Biochemical tests confirmed iatrogenic Cushing’s syndrome and clinical symptoms resolved after stopping ritonavir and tapering down the levels of corticosteroid with eventual discontinuation. Poor outcomes in these cases can be attributed to miscommunication and a lack of clear medical guidelines, as well as the fear of disclosure among patients with sensitive diagnoses. This case highlights the importance of taking a full and thorough drug history, and the risks associated with polypharmacy in patients.