Effect of rifampicin administration on CYP induction in a dermatomyositis patient with vasospastic angina attributable to nilmatrelvir/ritonavir-induced blood tacrolimus elevation: A case report.

Ritonavir (RTV), which is used in combination with nilmatrelvir (NMV) to treat coronavirus disease 2019 (COVID-19), inhibits cytochrome P450 (CYP) 3A, thereby increasing blood tacrolimus (TAC) levels through a drug-drug interaction (DDI). We experienced a case in which a DDI between the two drugs led to markedly increased blood TAC levels, resulting in vasospastic angina (VSA) and acute kidney injury (AKI). Rifampicin (RFP) was administered to induce CYP3A and promote TAC metabolism. A 60-year-old man with dermatomyositis who was taking 3 mg/day TAC contracted COVID-19. The patient started oral NMV/RTV therapy, and he was admitted to the hospital after 4 days because of chest pain and AKI. On day 5, his blood TAC level increased markedly to 119.8 ng/mL. RFP 600 mg was administered once daily for 3 days, and his blood TAC level decreased to the therapeutic range of 9.6 ng/mL on day 9, leading to AKI improvement. Transient complete atrioventricular block and nonsustained ventricular tachycardia were present during chest pain. In the coronary spasm provocation test, complete occlusion was observed in the right coronary artery, leading to a diagnosis of VSA. VSA and AKI are possible side effects of high blood TAC levels caused by DDI, and attention should be paid to cardiovascular side effects such as VSA and AKI associated with increased blood levels of TAC when it is used together with NMV/RTV. When blood levels of TAC increase, oral RFP can rapidly decrease TAC blood levels and potentially reduce its toxicity.