New Antiviral Drugs Treat COVID

Marking another amazing advancement in medicine, two new oral drugs are now available to treat COVID-19 infections within the first five days of symptoms: molnupiravir (mole-nyu-peer-uh-veer) and Paxlovid (packs-loh-vid). It may seem like these have taken a while to develop, but that’s because scientists have spent a ton of time studying the safety and effectiveness of the medications.
This is exciting news. But, as with all new medical treatments, I’m sure you have questions. Hopefully I can answer some of them for you.
 I want to start by briefly explaining the difference between antivirals and antibiotics. The word ‘antibiotic’ comes from the Greek roots anti- (meaning ‘against’) and -bios (meaning ‘life’.) In the true sense of the Greek roots, antibiotic’ could mean any chemical that inhibits growth of living organisms – antivirals, antibacterials, antifungals, antiparasitics. Today we use it to mean medications that treat bacterial infections, but a more accurate term would be ‘antibacterial’ – drugs that kill bacteria. This is why doctors rarely prescribe antibiotics for short-lived cold symptoms; it’s probably a viral infection, and antibiotics won’t work on a virus.

So, that brings us to antiviral drugs – drugs that kill viruses.

First, let’s learn what medications are available and how they work. The first, Paxlovid, is a combination of two drugs – nirmatrelvir and ritonavir. Nirmatrelvir blocks a protein in Sars-CoV-2, making the virus unable to reproduce itself. Ritonavir just stops the metabolism (breakdown) of nirmatrelvir so the levels of that drug stay high enough for long enough to make sure Sars-CoV-2 has been successfully treated.
The second, molnupiravir, works by weaseling its way into the RNA of the Sars-CoV-2 virus and causing errors every time the virus tries to reproduce itself.
Both must be started within the first five days of symptoms.
Another antiviral, remdesivir, has also recently been recommended for outpatient use in people with COVID-19 who are at high risk of serious disease. Because remdesivir requires an IV infusion over three consecutive days at hospital-based facility, it is less convenient yet recommended by the CDC as the intermediate antiviral option if Paxlovid is not available and before molnupiravir.
An obvious question is, “How effective are the oral antivirals?” The answer depends on which drug we’re talking about. Paxlovid reduces the risk of hospitalization or death by 85%, and molnupiravir, by 30%. I know what you’re thinking; those are very different levels of efficacy. So, why would anyone choose molnupiravir? Because it’s the simpler of the two.
Paxlovid has a long list of drug interactions that limit its use, and it can’t be used in severe kidney disease, any liver disease, or in certain HIV-positive patients. However, it can be used safely in pregnancy. Molnupiravir, while less effective overall, is pretty boring when it comes to who can and can’t take it. The only people who cannot take molnupiravir are pregnant persons (risk to baby) and persons under age 18 (risk to bone and cartilage growth). There are some recommendations for using back up birth control during the treatment course and for specific periods of time afterward in people capable of becoming pregnant.
The common side effects of Paxlovid and molnupiravir are very mild- things like GI upset, dizziness, muscle aches, taste changes, and possibly higher blood pressure.
Let’s be clear: this is excellent news and marks another step toward ending this pandemic. But these medications are not – I repeat, NOT – a replacement for vaccines. It’s not a good idea to wing it and just take the treatment if you get sick. First, the drugs are in limited supply. Second, their use is limited based on risk groups and will be prioritized for those at highest risk of severe illness or death. Third, risking getting sick because there’s a treatment available can backfire in so many ways. The treatment might not be effective for you, you might be too late to get it, it might not be available, or you might not be eligible for it at this time. And finally, the immunity you get from an infection doesn’t compare to that from a vaccine.
The most effective way to decrease COVID-19 infections is to prevent them in the first place. We do that by limiting exposure to others, washing our hands, and wearing a mask to catch our respiratory droplets. But Sars-CoV-2 is a beastly thing, and it often can bypass those measures. That’s where vaccines come in. Vaccines won’t necessarily stop you from getting infected (and were not designed with that goal in mind), but they will likely decrease the severity and duration of your symptoms and keep you out of the hospital and not dead. Think of vaccines like a fire extinguisher; it’s not going to stop your house from catching on fire, but it’ll stop it from burning to the ground.

Kayla D. Richardson, MD is the Chief Medical Officer at River Valley Health & Dental in Williamsport, PA.
Published: 2/5/22

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