Answer
Nirmatrelvir directly blocks a protease needed for SARS-CoV-2 replication. Ritonavir slows nirmatrelvir's breakdown and increases its exposure.
Sources for this answer
- Paxlovid 150 mg/100 mg film-coated tablets — Current selected SmPCemc · Summary of Product Characteristics
General medicine information. Follow the instructions for your own medicine and speak to a pharmacist or clinician about your individual circumstances.