Tehran University of Medical Sciences Journal of Pharmaceutical Care 2322-4630 13 4 2025 12 31 322 325 Ignacio Patier Ruiz Department of Clinical Pharmacy, Hospital Universitario Clínico Lozano Blesa, Zaragoza, Spain. Roberto Lozano Ortiz Department of Clinical Pharmacy, Hospital Universitario Clínico Lozano Blesa, Zaragoza, Spain. Carlos Ignacio Díaz-Calderón Horcada Department of Clinical Pharmacy, Hospital Universitario Clínico Lozano Blesa, Zaragoza, Spain. 2025 08 20 2026 05 07 Red yeast rice (RYR) is increasingly used for cholesterol management but contains monacolin K, which is chemically identical to lovastatin, and may interact with antiretroviral therapy via CYP3A4 and P-glycoprotein pathways. We report the case of a 47-year-old man with well-controlled HIV-1 infection receiving dolutegravir/ abacavir/lamivudine who experienced virological rebound after self-initiating RYR supplementation. Eight weeks after starting RYR (77.7 mg daily, with a labeled monacolin K content of 3 mg), the patient developed virological rebound (897 copies/mL) despite confirmed adherence and absence of resistance mutations. Following pharmacist-led discontinuation of RYR, viral suppression (<50 copies/mL) was restored within eight weeks without modification of antiretroviral therapy. This represents the first documented case of RYR-associated virological failure in HIV treatment. Hospital pharmacists should routinely screen for herbal supplements and provide patient education regarding potential interactions with antiretroviral medications. https://jpc.tums.ac.ir/index.php/jpc/article/view/886 https://jpc.tums.ac.ir/index.php/jpc/article/download/886/443