Preventing Cushing: Iatrogenic Cushing Syndrome due to Ritonavir-Fluticasone Interaction

Ritonavir is commonly used in low doses to boost plasma levels of protease inhibitors in patients with human immunodeficiency virus (HIV) infections. It is also a potent inhibitor of cytochrome P450. We present a 50-year-old African American male with past medical history of HIV on highly active antiretroviral therapy (HAART), which also included ritonavir and long standing asthma that has been treated with inhaled fluticasone, who presented with back pain. He had central obesity, prominent abdominal striae and wasted extremities on physical examination. Laboratory tests showed low morning serum cortisol and suboptimal cosyntropin test consistent with adrenal insufficiency. Computed tomography (CT) of the spine showed a fracture of inferior endplate of the lumbar (L3) vertebra. The cause of osteoporosis is believed to be iatrogenic Cushing syndrome caused by enhanced levels of inhaled fluticasone effects secondary to inhibition of cytochrome P450. The patient was managed surgically and fluticasone was discontinued.