Warning about Paxlovid in transplant recipients

Paxlovid (nirmatrelvir) is recommended as a treatment for COVID-19 for patients at high risk of severe disease. However, Paxlovid significantly increases the serum concentrations of calcineurin inhibitors (e.g. cyclosporin, tacrolimus). Calcineurin inhibitors (CNI) are immunosuppressive medications which are commonly given in the setting of solid-organ transplantation, and certain autoimmune diseases.

Locally, we have seen recent cases of calcineurin inhibitor toxicity due to Paxlovid co-administration, with CNI serum levels reaching >15 times the therapeutic window.

Toxicities include acute kidney injury, tremor, hypertension, neurotoxicity, and thrombotic microangiopathy.

As winter approaches and COVID cases will invariably increase, we would like to remind our practitioners to please consult the treating specialist (e.g. nephrologist, transplant physician, rheumatologist) prior to commencing Paxlovid in patients taking CNIs.

See COVID-19 Medications pathway for more information.