Endocrine Abstracts

Potent drug–drug interactions between corticosteroids and pharmacokinetic boosters used in antiretroviral therapy (ART) are well recognised but often overlooked. Cobicistat, a strong CYP3A4 inhibitor, markedly reduces steroid clearance, predisposing to iatrogenic Cushing’s syndrome and adrenal suppression even after a single local injection.

Case Presentation: A 44-year-old woman with HIV, diagnosed in 2012 and on ART since 2015, had sequential regimen changes due to intolerance and resistance. In 2021 she was switched to Symtuza® (darunavir/cobicistat/emtricitabine/tenofovir alafenamide) plus dolutegravir. She experienced chronic gastrointestinal side effects on multiple regimens. The hand pain team consulted about corticosteroid injection for musculoskeletal symptoms. Potential risks of adrenal suppression with concomitant cobicistat therapy were highlighted; however, the patient proceeded with injection. Subsequently, she developed symptomatic adrenal insufficiency. A short Synacthen test confirmed inadequate adrenal reserve, necessitating endocrine referral and hydrocortisone replacement.

Discussion: This case emphasises the significant clinical impact of cobicistat–steroid interactions. Local corticosteroid administration can result in prolonged systemic steroid exposure in patients on boosted ART, leading to adrenal suppression and crisis risk. Management requires endocrine involvement, hydrocortisone replacement, and patient education regarding stress dosing. Preventive measures include avoidance of CYP3A4-metabolised corticosteroids and consideration of safer alternatives, such as beclometasone.

Conclusion: Cross-specialty awareness of ART–steroid interactions is essential. Proactive communication between HIV, endocrine, and other specialist teams can prevent iatrogenic harm in this vulnerable population.