CYP3A4 and COVID-19: Strong, moderate, and weak inhibitors increase the AUC of sensitive substrate by ≥5-fold, ≥2-fold to <5-fold, and ≥1.25-fold to <2-fold, respectively.14 For example, ritonavir (used with nirmatrelvir for COVID-19) is a strong inhibitor of CYP3A4.