Paxlovid is an oral antiviral treatment for mild-to-moderate COVID-19. It is a prescription medication designed to help prevent severe illness, hospitalization, and death in individuals at high risk.
Understanding Paxlovid’s Action
Paxlovid is a combination of two antiviral medications: nirmatrelvir and ritonavir. Nirmatrelvir is the primary active component, functioning as a SARS-CoV-2 main protease (Mpro) inhibitor. This enzyme is crucial for the virus’s ability to replicate within the body. By inhibiting Mpro, nirmatrelvir disrupts the viral replication process, thereby reducing the viral load.
Ritonavir, the second component, acts as a “booster” for nirmatrelvir rather than directly fighting the virus. It inhibits a liver enzyme (CYP3A) that metabolizes many drugs, including nirmatrelvir. By slowing nirmatrelvir’s breakdown, ritonavir increases and prolongs its concentration in the bloodstream, maintaining effective levels. This combined action stops the virus from multiplying, improving symptoms and reducing severe disease progression.
Eligibility and Administration
Eligibility for Paxlovid focuses on individuals at high risk for severe COVID-19. This includes people aged 50 and older, with risk increasing significantly for those over 65. Individuals with underlying medical conditions like chronic lung diseases, heart conditions, diabetes, or those who are immunocompromised are also high-risk. Paxlovid is authorized for individuals aged 12 and older weighing at least 88 pounds (40 kg) who have tested positive for SARS-CoV-2.
Treatment must begin as soon as possible after diagnosis and within five days of symptom onset. The standard dosage is two nirmatrelvir tablets (150 mg each) and one ritonavir tablet (100 mg) together, twice daily, for five consecutive days. These tablets should be swallowed whole, with or without food. Adhere to the five-day course, taking doses at approximately the same time each morning and evening. If a dose is missed by less than eight hours, take it when remembered; otherwise, skip it and take the next dose at the regular time.
Important Considerations for Use
Paxlovid can cause side effects, most of which are mild and temporary. The most frequently reported include an altered sense of taste, often metallic or bitter, and diarrhea. Other possible side effects are headaches, nausea, vomiting, abdominal pain, and a temporary increase in blood pressure. Allergic reactions are rare but can occur, such as hives, rash, swelling, or trouble breathing, requiring immediate medical attention. Liver damage is a less common but possible serious side effect, particularly for individuals with existing liver problems.
Paxlovid has potential for numerous drug interactions. Ritonavir, which boosts nirmatrelvir levels, can also increase the concentration of many other medications, potentially leading to serious reactions. Patients must inform their healthcare provider about all medications, including over-the-counter drugs, herbal supplements like St. John’s wort, and recreational drugs. Common categories of interacting drugs include statins, heart and blood pressure medications, some mental health medications, anti-seizure drugs, and blood thinners. In some cases, a healthcare provider may temporarily pause other medications or adjust their dosages while a patient is taking Paxlovid.
Some individuals may experience “COVID-19 rebound” after completing Paxlovid treatment. This is a recurrence of symptoms or a positive test after initial improvement. While reasons for rebound are still being studied, it is not considered a Paxlovid side effect, as it can also occur in individuals who did not receive treatment. Rebound symptoms are typically mild and usually resolve within days without further intervention. If rebound occurs, follow isolation guidelines to prevent potential transmission.