The combination of nirmatrelvir tablets and ritonavir tablets is a product that the FDA is allowing to be given for emergency use to treat COVID-19. The product is also approved to be used in Canada to treat COVID-19. It is used by people who have recently tested positive for coronavirus, have had mild to moderate symptoms for no more than 5 days and are not hospitalized. To receive this product you must also be at high risk for COVID-19 complications due to older age, obesity, or ongoing medical conditions (such as lung or heart disease or diabetes, among others). Talk to your doctor about the risks and benefits of treatment with nirmatrelvir and ritonavir.Nirmatrelvir is a SARS-CoV-2 main protease inhibitor. It works by preventing the growth of the virus that causes COVID-19. Ritonavir increases ("boosts") the levels of nirmatrelvir. This helps nirmatrelvir work better. More information about nirmatrelvir and ritonavir is available from the FDA Fact Sheet for Patients, Parents, and Caregivers for Emergency Use and from the Health Canada Patient Medication Information sheet.There is limited information about how safe and effective the combination of nirmatrelvir and ritonavir is for treating COVID-19.