Nirmatrelvir is an antiviral medication used in combination with ritonavir to treat certain viral infections. This co-packaged medication works to limit the spread of viruses within the body. It is administered orally.
Primary Medical Use
Nirmatrelvir is primarily used to treat mild to moderate COVID-19. The medication aims to reduce the risk of severe illness, hospitalization, or death in individuals at high risk for progression to severe COVID-19.
In high-risk individuals with COVID-19, nirmatrelvir/ritonavir has been shown to reduce the risk of hospitalization or death by approximately 88% when taken within five days of symptom onset. The medication also contributes to a quicker recovery, with individuals testing negative for COVID-19 about two and a half days earlier than those who do not receive the treatment. This antiviral therapy is considered a first-line treatment for eligible outpatients.
How Nirmatrelvir Works in the Body
Nirmatrelvir functions as a protease inhibitor, targeting the SARS-CoV-2 main protease (Mpro). This enzyme processes large viral proteins into smaller, functional units for viral replication. By inhibiting Mpro, nirmatrelvir prevents the virus from correctly assembling new viral particles, halting its spread.
Ritonavir enhances nirmatrelvir’s effect. It acts as a strong inhibitor of the CYP3A enzyme, which metabolizes nirmatrelvir. By slowing down the breakdown of nirmatrelvir, ritonavir increases and maintains higher concentrations of nirmatrelvir in the bloodstream, allowing it to have a more sustained antiviral effect. This ensures nirmatrelvir remains active for a longer duration, providing continuous viral suppression.
Eligibility for Treatment
Eligibility for nirmatrelvir treatment for COVID-19 is determined by several factors, focusing on individuals at high risk for severe disease progression. The medication is authorized for people aged 12 years and older who weigh at least 40 kilograms (88 pounds). Treatment should begin as soon as possible after a positive COVID-19 test and within five days of symptom onset.
Individuals considered at high risk for severe COVID-19 include those aged 50 and above, or those with certain medical conditions. These conditions include:
Diabetes
Cancer
Coronary artery disease
Chronic lung diseases
Pregnancy
People who are immunocompromised or on immunosuppressant drugs also fall into the high-risk category. Consulting a healthcare provider is important to determine if an individual meets the specific criteria for this treatment.
Important Considerations for Patients
Nirmatrelvir is administered orally as co-packaged tablets, taken twice daily for five days. Patients take two nirmatrelvir tablets along with one ritonavir tablet at each dosing time. It is important to swallow the tablets whole and not to split, chew, or crush them. The medication can be taken with or without food, but taking it with food may help if stomach upset occurs.
Common side effects of nirmatrelvir/ritonavir include changes in taste perception, diarrhea, high blood pressure, muscle pain, nausea, vomiting, headache, and general discomfort. Patients should complete the entire five-day course of medication, even if their symptoms improve, to ensure full treatment of the infection.
Drug interactions are an important consideration due to ritonavir’s potent enzyme inhibition profile. Ritonavir can affect how other medications are metabolized, potentially leading to increased or decreased levels of co-administered drugs. Patients should provide their healthcare team with a comprehensive list of all current medications, including over-the-counter drugs and supplements, to screen for potential interactions. Adjustments to nirmatrelvir dosage may be necessary for patients with kidney disease.