Oral antiviral treatments for COVID-19 help manage the illness for certain individuals. These medications are taken at home to prevent progression to severe disease, which could otherwise necessitate hospitalization. They offer early intervention, easing the burden on healthcare systems.
Available COVID-19 Antiviral Pills
Two oral antiviral medications for COVID-19 treatment are Paxlovid and Lagevrio, also known as molnupiravir. Paxlovid is a combination therapy of two drugs: nirmatrelvir and ritonavir. Nirmatrelvir functions as a protease inhibitor, while ritonavir enhances nirmatrelvir levels.
Molnupiravir, marketed as Lagevrio, is a nucleoside analogue. Paxlovid has received full FDA approval for adults, while molnupiravir is authorized for emergency use.
How the Pills Work
Paxlovid works by directly interfering with the SARS-CoV-2 virus’s ability to replicate within the body. Its active component, nirmatrelvir, targets and blocks an enzyme called the main protease (Mpro), which the virus needs to process long protein chains into smaller, functional proteins. Without this enzyme, the virus cannot properly assemble new copies of itself, effectively halting its spread. The second drug in Paxlovid, ritonavir, does not directly fight the virus but rather slows down the breakdown of nirmatrelvir in the liver. This boosting effect ensures that nirmatrelvir remains in the bloodstream at sufficiently high concentrations for a longer duration, maximizing its antiviral action.
Molnupiravir employs a distinct mechanism to combat the virus, known as “lethal mutagenesis” or viral error induction. Once inside human cells, molnupiravir is converted into its active form, a nucleoside triphosphate. This active molecule then acts as a faulty building block during the virus’s replication process, specifically when the viral RNA-dependent RNA polymerase enzyme attempts to create new genetic material. The incorporation of these incorrect building blocks introduces numerous errors into the virus’s genetic code, leading to a cascade of mutations that render new viral particles non-functional and prevent further replication.
Eligibility and Prescription Process
Eligibility for COVID-19 antiviral pills is limited to individuals diagnosed with mild-to-moderate COVID-19 who have specific risk factors for developing severe disease. These risk factors include advanced age, a weakened immune system, or chronic medical conditions such as heart disease, diabetes, or chronic kidney disease. It is also required that treatment be initiated within five days of the onset of symptoms or a positive COVID-19 test result for maximum effectiveness.
These medications are available by prescription only, emphasizing the need for a healthcare provider’s assessment. Patients can obtain a prescription by contacting their primary care physician. Another option is visiting “Test to Treat” locations, which are sites that can provide both a COVID-19 test and, if appropriate, an immediate prescription for antiviral medication. Some pharmacists are also authorized to prescribe Paxlovid directly, often requiring access to recent medical records and a comprehensive list of all current medications to ensure safety. Beginning the medication as soon as possible after diagnosis is important for achieving the best outcomes.
Efficacy and Potential Side Effects
Paxlovid has demonstrated significant effectiveness in clinical trials, particularly in reducing the risk of severe outcomes. The EPIC-HR trial showed an 89% reduction in COVID-19-related hospitalization or death among high-risk, unvaccinated individuals when started within five days of symptom onset. Real-world studies also support its effectiveness, even in vaccinated populations, with one report indicating a 51% lower hospitalization rate for treated adults compared to those who did not receive the drug.
Molnupiravir’s efficacy has shown variability across studies, with the MOVe-OUT trial reporting a 30% reduction in hospitalization or death in unvaccinated, high-risk patients. While some analyses suggest it can accelerate clinical recovery, other large-scale trials, such as the PANORAMIC study which included vaccinated individuals, did not find a significant reduction in hospitalization or death rates.
Paxlovid commonly causes an altered sense of taste, frequently described as metallic or bitter (“Paxlovid mouth”). Other common side effects include diarrhea, headaches, nausea, abdominal pain, and a temporary increase in blood pressure. Less frequent but serious side effects can include liver problems (particularly for individuals with pre-existing liver conditions) and allergic reactions.
Molnupiravir’s common side effects include nausea, diarrhea, and dizziness. Headaches are also a reported side effect. Molnupiravir is generally considered to have fewer drug interactions compared to Paxlovid. However, it is not recommended during pregnancy due to potential harm to an unborn baby. Both men and women are advised to use reliable contraception during treatment and for a period afterward.
A significant consideration for Paxlovid is its potential for numerous drug interactions. Ritonavir, a component of Paxlovid, can inhibit liver enzymes responsible for metabolizing many other medications, leading to elevated levels of co-administered drugs in the body. This interaction can result in serious or even life-threatening adverse reactions with medications such as statins, heart rhythm drugs, anti-seizure medications, and immunosuppressants. Patients must disclose all current medications, including over-the-counter drugs and supplements, to their healthcare provider or pharmacist to identify and manage potential interactions.
The phenomenon of “COVID rebound” refers to a recurrence of COVID-19 symptoms or a new positive test result after an initial improvement or negative test. This rebound typically occurs between two and eight days after initial recovery or completing treatment. Research suggests that COVID rebound can occur regardless of whether a person received Paxlovid or was vaccinated, indicating it may be part of the natural course of SARS-CoV-2 infection for some individuals. While some studies show similar rebound rates between treated and untreated groups, others report a higher incidence of virologic rebound in Paxlovid users. Generally, rebound symptoms are mild and tend to resolve within about a week, and current public health guidance does not recommend additional antiviral treatment for rebound.