Antiviral drugs are often confused with antibiotics, as feverish sore throats and days of misery come and go.
Antibiotics target bacteria. Antivirals target specific viruses.
That’s an important distinction. A herpes pill won’t cure the flu; an HIV drug won’t banish shingles. There is no antiviral analogous to “something strong for the infection.”
The doctor had better know — or guess — which virus is calling the shots.
Why are viruses so hard to target?
Bacteria are living cells that make things happen. There are plenty of ways to interfere with that process.
Viruses are more like parasites , exploiting living cells to make more viruses. An effective antiviral drug has to interfere with that process without killing the cell in the process.
There are different ways to do that. Some drugs target an earlier step in the process, others later ones, but all have to do with either getting the virus inside the cell or getting that cell to make more viruses. That’s why there are so many different antiviral drugs out there — each targets a specific step in the life cycle of a specific virus.
Unlike antibiotics, which often have a broad effect, antivirals usually have a narrow mechanism.
Herpes drugs keep viruses at bay
The herpes virus family is the target of several antiviral drugs, notably acyclovir and its relatives. These drugs are used to treat cold sores, genital herpes, and shingles. They can make outbreaks shorter and less severe, particularly if treatment is started early. That means starting the drug at the first tingling in the case of cold sores or within 72 hours of the appearance of blisters in shingles. However, it’s important to note that these drugs do not eradicate the virus, only shorten the length of an outbreak. The herpes virus stays with you (in your nerve cells) and can be reactivated later. Some people take these drugs only when an outbreak is coming on, while others take a daily dose to prevent outbreaks and reduce the chance of transmitting the virus to a sexual partner. Note that that reduced chance is not zero — outbreaks can occur without warning.
Acyclovir and valacyclovir are both converted to the same active drug in the body; the difference is that valacyclovir has better absorption, so it can be dosed less frequently.
Flu drugs act fast, not far
Influenza is the target of several different antiviral drugs: oseltamivir, zanamivir, peramivir, and baloxavir. The truth is that these drugs don’t work that well for uncomplicated flu in otherwise healthy people. If you’re an adult who was already feeling better, it’s probably not worth it. However, if you are pregnant, elderly, very sick, or have heart, lung, or immune problems, the risks may outweigh the costs. Moreover, early intervention reduces the risk of complications — and for frail or immunocompromised patients, it may still be worthwhile even if more than 48 hours have passed since the start of symptoms. For uncomplicated flu, that’s the period in which antivirals make the most difference: the first 48 hours after symptom onset.
Note that these drugs are ineffective against the common cold. Both cold and flu viruses cause similar symptoms, so a test or clinical judgment may be necessary to distinguish between them.
COVID antivirals raise more questions than they answer
Paxlovid (nirmatrelvir/ritonavir) is an antiviral drug for the treatment of COVID, indicated in certain populations (in people at high risk of developing severe forms of the disease). Dosing should begin as early as possible after diagnosis, since the clinical benefit of the drug decreases as the disease progresses. Ritonavir, one of the two active ingredients in Paxlovid, inhibits certain liver enzymes (CYP3A). This affects the metabolism of many other drugs, which can lead to dangerous increases in their concentrations in the blood. This is especially important for cholesterol-lowering drugs (statins), drugs acting on the heartbeat or blood clotting, anti-epileptic drugs, or immunosuppressive drugs after organ transplant surgery. You shouldn’t stop taking your regular medications just because you’ve been prescribed Paxlovid, since the interaction could be life-threatening. The decision to stop or avoid certain medications should be made jointly with a pharmacist or doctor.
Other COVID antivirals include remdesivir (administered intravenously) and molnupiravir (for eligible patients). Treatment options for COVID-19 are limited to authorized drugs, which should be prescribed with due consideration of contraindications and warnings. Eligibility for treatment with these drugs depends on age, pregnancy, and kidney or liver function.
Some antivirals are for life
Many HIV treatments are designed to be taken for life, with occasional interruptions. In reality, HIV treatment is far more nuanced. HIV treatment usually consists of a combination of different antiviral drugs that inhibit HIV replication at different stages. Taking multiple HIV drugs allows the body to maintain lower levels of the virus and reduces the likelihood that the virus will become resistant to any one drug. Moreover, suppressing the replication of HIV is critical to preserving the immune system. HIV drugs must be taken regularly — missing doses allows the virus to replicate and resist drug treatment.
Long-term suppression of the virus is also required in hepatitis B. Chronic hepatitis C, on the other hand, is curable with a course of direct-acting antiviral agents.
So, antiviral treatment can be short-term — for example, the five-day course for influenza. It can also be long-term (several months) — for example, the treatment of hepatitis C. It can last a lifetime — HIV treatment often involves taking multiple drugs every day. That’s why the entire category of antiviral drugs is so broad.
Side effects vary from drug to drug
Nausea, headaches, and gastrointestinal discomfort are typical side effects of many antivirals, but are not universal. However, there are side effects that are more specific to a given class of drugs. For example, impaired kidney function can be a side effect of drugs such as acyclovir or valacyclovir. Doses may need to be adjusted in patients with reduced kidney function, or the drug may not be prescribed to people with reduced kidney function. Dehydration is another risk factor for kidney damage. Liver function is also a concern with many antiviral drugs, as is the interaction between drugs in HIV and hepatitis treatment. However, these drugs are generally not used concurrently with other drugs.
Many women wonder if they can take antiviral drugs during pregnancy. In some cases, women should avoid these drugs. Remember, however, that both the flu and genital herpes can be dangerous during pregnancy. The doctor will evaluate the situation and weigh the risks and benefits. Obviously, you shouldn’t take your friend’s antiviral drugs — taking someone else’s medication is never a good idea. A few acyclovir tablets won’t help you with a viral infection of the respiratory tract, and your Paxlovid may be incompatible with your regular medications.
Do antivirals stop you from infecting others?
Sometimes, but rarely completely — it depends on the drug. In some cases, it simply reduces the chances. The person who has been treated for influenza remains infectious to others, as does the person who has been treated for genital herpes. HIV treatment is an example of a situation in which antivirals do eliminate contagion, but this requires regular monitoring and adherence to treatment. The fact that a person takes antiviral drugs does not free them from the need to observe all the rules of hygiene and behavior, as well as recommendations from sexologists.
You will find a selection of the most popular antiviral drugs below — but you shouldn’t start treatment without determining which virus is attacking you.
Antivirals are not antibiotics with another label; they are an entirely different class of drugs. Used properly, they will help you feel better and reduce the risk of complications. Even more importantly, they allow you to control many chronic viral infections throughout your life and even cure them — if you have the right antiviral drug.
