In a world where viruses can cause anything from the common flu to life-threatening conditions like HIV and COVID-19, antiviral medications play an essential role in managing certain viral infections — but understanding their purpose and limitations is necessary to help patients and providers make informed decisions.
From shortening the flu or reducing the severity of COVID-19 symptoms to controlling chronic conditions like herpes and HIV, antiviral medications play a vital role in modern medicine, but understanding their functions and limitations is essential for both patients and providers.
This article explores what antiviral drugs are, how they work and which viruses they are used to treat, their safety considerations, and more.
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What Are Antiviral Drugs?
Antiviral drugs are medications designed to combat viruses. Unlike antibiotics, which target bacteria, antivirals specifically interfere with a virus’s ability to replicate and spread in the body.
The first antiviral drug, idoxuridine, was approved in 1963; since then many antivirals have been created to treat diseases like the flu, HIV, hepatitis, and more.
Viruses are responsible for many diseases, ranging from the common cold to life-threatening illnesses like HIV and hepatitis. Antiviral drugs help slow down or stop the virus, giving the immune system a chance to fight back.
While antiviral drugs can slow or stop viral replication, but their effectiveness varies depending on the type of virus and the stage of infection.
Common Viral Diseases Treated with Antivirals
While over 200 human viruses have been discovered and three to four new viruses are detected yearly, not all viruses are treated with antiviral medication.
Viruses commonly treated with antiviral medications include:
- Human Immunodeficiency Virus (HIV): HIV causes AIDS; antivirals manage the infection and reduce viral replication.
- Hepatitis B Virus (HBV): in some people, HBV can cause chronic liver infections and complications like liver cancer.
- Hepatitis C Virus (HCV): HCV, which can cause chronic complications like liver cirrhosis and liver cancer, affects around 50 million people worldwide, with 1 million new cases every year, according to the World Health Organization (WHO). Direct-acting antiviral medicines (DAAs) can cure over 95% of cases, based on current treatment protocols and proper adherence.
- Herpes Simplex Virus (HSV): antiviral medications are available to treat type 1 HSV (oral herpes, or cold sores, which affects 64% of the global population) and type 2 HSV (genital herpes).
- Human Cytomegalovirus (HCMV): HCMV affects people with weakened immune systems, causing severe complications like vision loss, liver failure, lung infections, inflammation of the colon and esophagus, and brain and nerve damage, especially in people with weakened immune systems. It can also cause developmental problems in babies.
- Human Papillomavirus (HPV): HPV causes genital warts and cancers including cervical cancer.
- Influenza Virus: this includes seasonal flu (the common cold) and pandemic strains like H1N1.
- Respiratory Syncytial Virus (RSV): RSV causes respiratory infections, especially in young children and older adults.
- Varicella-Zoster Virus (VZV): VZV causes chickenpox and shingles.
- Ebola: antiviral medications are now available to treat Ebola.
Difference Between Antivirals and Antibiotics
Antiviral drugs are often confused with antibiotics. The key difference lies in their targets:
Antivirals
Antiviral medications treat viral infections by targeting viruses.
When To Use Antiviral Medications: typical viral symptoms often include fever, fatigue, muscle aches, cough, and runny nose. A low-grade fever may be present.
Antibiotics
These medicines treat bacterial infections by killing bacteria or stopping or slowing their growth.
When To Use Antibiotics: Bacterial symptoms are more likely to involve localized issues, such as a sore throat, skin redness, swelling, or pain, as seen in infections like strep throat or urinary tract infections. A fever may be present.
Understanding this distinction helps ensure appropriate medication selection, which is important because antibiotics are ineffective against viruses like the flu or COVID-19.
Classes of Antiviral Medications
Antiviral medications are grouped into classes based on their chemical structure, their mechanism of action (how they work), and what part of the viral process they target.
This system helps scientists and doctors understand how antiviral drugs work and which infections they can treat.
How Antiviral Drugs Work
Different antiviral drugs work differently to target specific viruses.
Mechanism of Action: How Do Antiviral Medications Work?
Antiviral drugs work by interfering with different steps in a virus’s life cycle. Here’s how they help:
- Stop Viruses From Entering Cells: some antivirals block the virus from attaching to or entering your cells, keeping the infection from starting.
- Prevent Viruses From Making Copies: many antivirals trick the virus by pretending to be pieces of DNA or RNA. When the virus tries to use these fake pieces, it can’t make new copies of itself. For example, Acyclovir blocks the virus’s ability to copy its DNA.
- Target Viral Enzymes: viruses rely on certain enzymes to grow and mature. Some drugs stop these enzymes from working, so the virus can’t finish its job. For example, protease inhibitors stop enzymes that help viruses like HIV make their building blocks.
- Block Viruses From Spreading: some antivirals stop viruses from leaving infected cells, which keeps them from spreading to other parts of your body.
- Boost Your Immune System: some drugs, like interferons, help your immune system fight the virus more effectively.
Over-the-Counter vs. Prescription Antivirals
Antiviral medications are only available as prescription medications, meaning they must be prescribed by a healthcare provider.
Certain natural products which are available over-the-counter (OTC) may act as supportive antiviral treatments, like zinc, or lysine for cold sores.
*A note about lysine: lysine supplementation at doses exceeding 3 grams per day, particularly when combined with a low-arginine diet, may help reduce the recurrence of cold sores, though research indicates that it is not effective for treating active lesions.
Consulting a healthcare provider ensures the right treatment for your condition.
Safety and Side Effects
Like all medications, antiviral drugs have specific safety concerns and potential side effects, although they can vary depending on the specific medication and individual patient factors.
Patients should consult a healthcare provider for personalized advice.
Potential Side Effects
Like all medications, antiviral drugs can cause side effects. Common side effects include:
Mild Side Effects: nausea, fatigue, headaches.
Serious or Severe Side Effects:
- Breathing problems (like bronchospasms)
- Allergic reactions
- Bone marrow suppression (decreased red or white blood cell production)
- Seizures or peripheral neuropathy (numbness and tingling)
- Neuropsychiatric symptoms (for example, strange behavior or thoughts like confusion or self-harm, which were mostly reported in teens and adults in Japan)
Long term use of antiviral medications can cause health problems. For example, using antiviral therapy for HIV over a long time can cause health problems like bone density loss, kidney damage, heart disease, liver issues, and trouble with memory or thinking.
These risks can get worse as people living with HIV age, so it’s important that they are regularly monitored by a healthcare professional and use newer, safer medications when possible and appropriate.
Contraindications
Different antiviral medications may have different potential drug interactions and contraindications. It’s essential to discuss your current medications with your prescribing provider to ensure that you are minimizing your risk of problems.
Certain individuals should avoid or use antivirals cautiously:
Pregnancy
ntiviral drugs should be used very carefully during pregnancy because some, like amantadine, are known to cause birth defects (teratogens). Other antivirals, like acyclovir, are considered safe in early pregnancy. Pregnant people should always discuss their health concerns and medication use with their doctor.
Breastfeeding
Discuss with your healthcare provider. Some drugs, such as acyclovir or valacyclovir, are not expected to cause harm to the breastfeeding infant. Your doctor can prescribe the right medication for your situation.
People With Liver or Kidney Disease
In patients with liver or kidney disease, the level of caution required may rely on the medication used.
Antiviral medicines like Remdesivir, Lopinavir-Ritonavir, Favipiravir and others often used to treat COVID-19 can raise liver enzymes (AST/ALT) in some people, but elevations are often reversible and they are not completely unsafe for patients with liver disease.
These medicines can still be used at the discretion of the ordering provider, but patients must be closely monitored for any signs of liver problems.
Antiviral medications are generally safe for people with kidney disease, including those with severe kidney problems or on dialysis, but they require careful monitoring. These patients should be closely monitored for rare side effects or interactions with other medicines during treatment.
People Taking Multiple Medications
Contraindicated drug interactions with direct-acting antivirals (DAAs) are rare but serious, occurring in about 2% of cases. Patients taking pharmaceuticals for any condition should discuss these with their ordering provider.
Always inform your provider about changes in your health, as well as other medications or supplements you’re taking to minimize risks.
Drug Interactions
Potential drug interactions may vary depending on the type of antiviral used, and the person’s current medications. Drug interactions are more common in older patients who take multiple medications (polypharmacy).
One study examining the likelihood of drug interactions with antivirals focused on patients with an average of 5.2 medications each.
This study found that common drugs that interact with antivirals include:
- Proton pump inhibitors (PPIs) used for acid reflux
- Calcium channel blockers for blood pressure (avoid amiodarone with the antiviral medication sofosbuvir, as this combination can cause fatal bradycardia, or heart slowing)
- Statins for lowering cholesterol (avoid this combination, as it may cause rhabdomyolysis, or severe muscle damage)
Patients taking antiretroviral medications to manage HIV may have additional drug interactions to be aware of, often because many medications are metabolized by the liver. These patients require regular monitoring, and any new or unusual symptoms should be reported to a medical provider.
Any patient using antiviral medications should report new symptoms or drug interactions to your doctor immediately.
Antiviral Drug Resistance: Key Insights
Antiviral drug resistance happens when viruses change (mutate) in ways that make medicines less effective. This is a big problem for chronic infections like HIV, hepatitis B, and herpes, where viruses stay in the body for a long time.
Resistance develops because viruses replicate quickly, and some mutations make them harder to treat. Missing doses or not finishing treatment can also allow resistance to grow.
How Resistance Affects Viruses
- HIV: resistance can affect all types of HIV drugs, which is why doctors use combination treatments with 3 or more drugs to treat HIV infections. Drug-resistant HIV can spread in untreated cases. Regular medical care and adherence to the proper treatment are necessary.
- Hepatitis B: the virus mutates quickly, especially with older medicines like lamivudine. Resistance can also weaken the effect of vaccines.
- Herpesviruses (like cold sores, shingles, and CMV): resistance is rare in healthy people but more common in those with weak immune systems, like transplant patients.
- Influenza (the flu): older flu medicines like amantadine often stop working because the virus quickly becomes resistant. Newer drugs must be used carefully to avoid the same problem.
How Resistance is Found
Doctors use tests to find resistance:
- Genotypic Tests: these tests look for specific mutations in the virus, but they might miss rare changes.
- Phenotypic Tests: phenotypic tests measure how well a drug stops the virus but take longer and are harder to do.
Why Resistance is a Problem
- Fewer Options: when a virus becomes resistant, doctors must use backup drugs that may not work as well.
- Toxic Side Effects: second-line treatments can cause serious problems, like kidney or bone marrow damage.
- Cross-Resistance: a mutation can make the virus resistant to several drugs at once.
How to Prevent Resistance
- Combination Therapy: using multiple drugs makes it harder for the virus to adapt.
- Take Medicine as Prescribed: missing doses lets the virus survive and build resistance.
- Develop Better Drugs: scientists are working on new medicines that target different parts of viruses to stop resistance.
Why It Matters
Drug resistance makes infections harder and more expensive to treat. Resistant viruses can spread to others, creating a bigger health problem.
Following treatment plans, testing for resistance, and making better medicines are key to fighting resistance and protecting everyone’s health.
Practical Takeaways
Patients with a simple viral infection are often able to recover at home with rest, fluids, and simple, healthy food.
When to Consult a Provider
Antiviral drugs can be lifesaving, but knowing when to seek medical advice is essential. Consult a healthcare provider if:
- You experience prolonged flu symptoms.
- You’re at high risk of complications from viral infections (e.g., elderly patients, immunocompromised individuals).
- You suspect exposure to serious viruses like HIV or hepatitis.
These recommendations are general guidelines. Always consult a healthcare provider for personalized advice.
How to Discuss Antiviral Use
When talking to your provider, ask:
- Is an antiviral the best option for my condition?
- What are the potential side effects?
- Are there alternatives?
- Should I be concerned about antiviral resistance?
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Key Takeaways
- Role of Antiviral Medications: antiviral drugs target viruses to help prevent replication and manage infections like HIV, influenza, and hepatitis.
- Safety Considerations: antiviral use requires careful monitoring in pregnant or breastfeeding patients, patients requiring long-term antiviral use, or patients with kidney or liver disease.
- Resistance Challenges: improper use of antivirals can lead to drug resistance; always take medications as directed.
Always consult a healthcare provider to determine the most appropriate treatment.
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