How Do Antiviral Medications Work?

Jan 4, 2023


Alto Pharmacy

Antiviral medications have fueled many medical breakthroughs since they were first introduced in the 1960s to treat viruses. Not only are they currently helping to reduce severe cases of Covid-19 and related hospitalizations, they have also made HIV a manageable chronic condition — and that’s only to name a few examples of the role they play in healthcare.

Take a look at how these medications treat and prevent viruses like Covid, the flu, HIV, hepatitis, and more. 

What are viruses?

A virus is a germ that causes an illness. It cannot survive on its own. In order to replicate and spread, it must infect healthy cells in your body.

Well-known diseases caused by viruses include:


  • The flu and common cold

  • Ebola

  • Herpes

  • Hepatitis B and C

  • Measles

  • Chickenpox and shingles

  • Covid-19

Viruses are distinct from bacteria. While antibiotics are highly effective at ending infections caused by bacteria, they cannot work on viruses. This is why the creation of antivirals was such an important medical advancement.

How do antiviral medications work?

Antiviral medications help your body fight a virus by disrupting the infectious agent’s replication process. They function differently depending on which virus they’re targeting. When used to treat the flu or Covid, for instance, they can reduce the severity of symptoms and shorten the duration of the infection.

When treating chronic illnesses like HIV or herpes, antivirals cannot permanently end the infection. Rather, they lower the amount of the virus in your body — also referred to as your viral load — to control symptoms and prevent transmission.

When taken as prescribed every day, the antivirals used to treat HIV can help those with the condition maintain an undetectable viral load. This stops the progression of the illness and virtually eliminates the risk of transmitting it to others.

While they are not a substitute for vaccines, antivirals can also be used as a preventative measure against some viruses, as explained in more detail below.

The majority of antivirals are oral medications, but they can also be taken as an injection, intravenously, topically, or even as eye drops or an inhalant.

Many antivirals can safely be used by children as well as pregnant and breastfeeding individuals. Guidelines vary by medication. Consult with your provider about whether a specific antiviral is an option for you.

When should I take antivirals?

The duration and starting point of antiviral treatment varies by virus.

Treatment of short-term illnesses

The flu and Covid

Tamiflu® and Paxlovid®, which treat the flu and Covid, respectively, are typically prescribed for several days. In some cases, it’s necessary to take them for a week or more.

These medications are most effective if taken within two days of infection. However, it may still be beneficial to take them after two days, especially if you are at risk for complications.

The following factors may increase your risk of complications from the flu and/or Covid.

Health conditions

Other health factors

  • Obesity

  • Weakened immunity from illness or medications

  • Pregnancy

  • Age - adults 65 and older and children under two are most vulnerable


The antivirals used to treat the Ebola virus — Inmazeb® and Ebanga® — are administered as a single intravenous infusion.

Treatment of chronic illnesses

When used to treat chronic conditions such as HIV, hepatitis B or C, or herpes, antivirals must be taken on an ongoing basis, even in the absence of symptoms.

If you have received a diagnosis of a chronic condition caused by a virus, it’s important to begin treatment as quickly as possible to protect your health and others.

Prevention of illnesses

Some antiviral medications can protect against viral infections after potential exposure. PEP, or post exposure prophylaxis, is a medication taken within 72 hours of potential exposure to HIV to lower a person’s chances of contracting the virus. There are other medications that work similarly after potential exposure to the flu.

Antivirals may also be prescribed for individuals with HIV during pregnancy to prevent transmission from mother to baby. The baby will also likely receive antiviral treatment after it is born.

The importance of vaccines

While some antivirals can prevent a person from getting infected by a virus after potential exposure, they are not a substitute for vaccines, which offer ongoing protection against viruses. 

Additionally, while other antivirals reduce the severity of symptoms, vaccines are even more of a safeguard against virus-related health complications, as they prevent the initial infection altogether.

Check with your doctor about which vaccines you need. For detailed vaccine recommendations by age group, reference the CDC’s recommended immunization schedules for children and adolescents and adults.

Your partner in health

Managing any chronic condition is easier with a reliable pharmacy partner by your side. Our pharmacists have deep expertise in HIV treatment and prevention and can help you get started and stay on track with antiretroviral therapy as well as the preventative medication PrEP.

We will coordinate with your healthcare and insurance providers to ensure that you’re receiving the best option for your needs at the best price. Our pharmacists are also available to chat whenever questions come up about side effects or how to take your medication properly.

Reach out any time through in-app messaging or by phone at 1-800-874-5881.

This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or another qualified health provider with any questions you may have regarding a medical condition.

All third party trademarks (including logos and icons) referenced by Alto Pharmacy remain the property of their respective owners. Unless specifically identified as such, Alto’s use of third party trademarks does not indicate any relationship, sponsorship or endorsement between Alto and the owners of these trademarks.

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