Iatrogenic Adrenal Insufficiency Secondary to Combination Therapy with Elvitegravir/Cobicistat/Tenofovir Disoproxil Fumarate/Emtricitabine and Interlaminar Triamcinolone Injection in an AIDS Patient

We report the first identified case of suspected iatrogenic adrenal insufficiency after an interlaminar injection of triamcinolone acetonide while on concomitant Stribild (elvitegravir 150 mg/cobicistat 150 mg/tenofovir disoproxil fumarate 300 mg/emtricitabine 200 mg [EVG/c/TDF/FTC]). A 49-year-old female with HIV on EVG/c/TDF/FTC therapy presented to our endocrinology clinic to be evaluated for suspected Cushing syndrome. Prior to presentation, the patient had been given 2 interlaminar spinal injections of triamcinolone. Thereafter, she developed a swollen face, had unexplained weight gain, and fatigue. Cosyntropin stimulation test was positive for adrenal insufficiency. By applying the Naranjo Nomogram for Causality and the Drug Interaction Probability Scale to this drug–drug interaction, we calculated a score of 6 (probable) and 5 (probable), respectively. Symptoms resolved without further intervention. The EVG/c/TDF/FTC contains cobicistat, a strong cytochrome P450 3A4 (CYP3A4) inhibitor, which can potentiate drug interactions involving metabolizing of medications via this pathway. Clinicians are reminded to be vigilant while assessing the potential pharmacokinetic drug interactions not mentioned by the manufacturer.