Drug-drug interaction between remdesivir and immunosuppressant agents in a kidney transplant recipient.

A 60-year-old man was treated with a regimen of controlled-release tacrolimus (2 mg once daily), everolimus (0.5 mg twice daily), methylprednisolone (4 mg once daily), and mizoribine (100 mg twice daily) as an anti-rejection regimen following living-donor kidney transplantation. One year after transplantation, the recipient was admitted to Mie University Hospital (day X; admission date) to treat coronavirus disease 2019 pneumonia. The latest trough concentrations of tacrolimus and everolimus before admission (day X-65) were 4.5 ng/mL and 4.4 ng/mL, respectively. Since tacrolimus concentration was 4.2 ng/mL on day X+3, the dose was adjusted to 1.5 mg once daily to reach the target concentration of 3.0 ng/mL due to the introduction of remdesivir. After starting remdesivir on day X+4, the increased trough concentrations of tacrolimus on day X+6 (6.9 ng/mL) and everolimus on day X+7 (9.2 ng/mL) were observed, which resulted in dose reduction of tacrolimus (0.5 mg once daily) and discontinuation of everolimus. After discontinuation of remdesivir on day X+9, dose titration of controlled-release tacrolimus and restart of everolimus (0.5 mg twice daily) were performed from day X+15. The dose of controlled-release tacrolimus was titrated and fixed to 2 mg once daily at discharge (day X+21). There was no toxicity due to immunosuppressive agents during hospitalization. This case report indicated that remdesivir might interact with cytochrome P450 3A4 substrates, such as tacrolimus and everolimus, and elevate their blood concentrations under high inflammatory conditions.