Nirmatrelvir is extracted from the body through its interaction with enzymes in the liver, primarily the CYP 3A4. This enzyme is the primary means of elimination of pharmaceuticals in the body. If the binding to this enzyme is too high then the lifetime of Nirmatrelvir will be short and not effective at small dose to inhibit SARS-Cov-2 viral replication. This in fact is an issue with Nirmatrelvir, and Ritonavir was added to inhibit normal liver function and activate the active drug. The score distribution of Nirmatrelvir and CYP 3A4 is given in Figure .