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Antiviral Medications

Reference Guide for Antiviral Medications

by BidRx Team
written by BidRx Team
Doctor explaining something to the patient

Highlights

  • Antiviral medications are used to manage viral infections and can’t help against bacterial or fungal infections.
  • Antivirals are generally only available by prescription, usually in pill or topical form.
  • Most antivirals are targeted towards specific infections, although there are a few “broad-spectrum” antivirals.
  • BidRX can help you get the best price on your antiviral medication.

Viral infections are some of the most common in the world, and among the most dangerous. Two of the worst epidemics in the last forty years, HIV/AIDS and COVID-19, were caused by viruses. Antivirals are a key tool to help stop infections, lower the odds of spreading a virus, and save lives.

Getting a test completed.

About Antivirals

Antivirals are part of the antimicrobial family of drugs, which include antibiotics and antifungals. An antiviral will not treat a bacterial infection like strep throat, or a fungal infection, like athlete’s foot. 

Antivirals generally don’t destroy an infection, but they do prevent it from multiplying. A viruside can destroy infectious agents but are so dangerous to the body that they’re only used externally. In general, antivirals are “narrow-spectrum,” often so narrow they only work on one type of virus.

Just like antibiotics, viruses can develop resistance to antivirals over time. You should complete the full course of an antiviral — even if you feel better — to help limit the spread of resistance.

Classes of common antivirals include:

  • Adamantane antivirals
  • Antiviral interferons
  • Chemokine receptor antagonists
  • Integrase strand transfer inhibitors
  • Neuraminidase inhibitors
  • Non-nucleoside reverse transcriptase inhibitors (NNRTIs)
  • (Nonstructural protein 5A) NS5A inhibitors
  • Nucleoside reverse transcriptase inhibitors (NRTIs)
  • Protease inhibitors
  • Purine nucleosides
Putting on a PPE mask.

Adamantane Antivirals

Adamantane was discovered in petroleum in 1933, with the first drug, the antiviral amantadine, released in 1967 to treat influenza A. The other common adamantane antiviral, rimantadine, was first put on the market in 1993, also targeting influenza A. Amantane drugs are also used to treat acne, diabetes, Parkinson’s disease, and Alzheimer’s disease.

Adamantane antivirals prevent replication of the flu virus by binding to specific amino acids in the virus and preventing it from shedding its outer membrane to replicate. 

Amantadine is no longer recommended in most situations as an antiviral, as the flu virus has largely developed resistance to it. Rimantadine is also beginning to show resistance to the flu, although it’s still effective against other respiratory viruses and is being researched as a treatment for hepatitis C. It also has fewer and less-severe side effects than amantadine.

Warnings and Contraindications — Adamantane Antivirals

If you have liver or kidney disease, only use adamantane antivirals under doctor’s orders and under a doctor’s supervision. As they haven’t been researched for use during pregnancy, these antivirals aren’t recommended for people who are pregnant or considering pregnancy.

Side Effects — Adamantane Antivirals

Common side effects of adamantanes include:

  • Nausea
  • Exhaustion
  • Lightheadedness
  • Insomnia
  • Difficulty with concentration and confusion
  • Anxiety

Drug Interactions — Adamantane Antivirals

Acetaminophen (Tylenol) and aspirin may inhibit the action of adamantanes.

Don’t take a nasal flu vaccine during a course of adamantanes or for 48 hours after you complete the course.

Holding a red pill.

Antiviral Interferons

Interferons are created naturally by the body as a defense mechanism. When a cell is infected, it sends out interferons to alert other cells and help prevent viral spread. Synthetic interferons were developed to target specific viruses, most commonly herpes simplex and hepatitis B and C. 

Interferons are also used to treat autoimmune conditions such as multiple sclerosis and some cancers. The two most common antiviral interferons are peginterferon alfa-2a (Pegasys) and  peginterferon alfa-2b (PegIntron, Sylatron) and can be taken at home via injection.

Due to the risks involved with interferons, they’re generally only used in life-threatening situations or the absence of other options.

Warnings and Contraindications — Antiviral Interferons

If you are sexually active with the possibility of pregnancy, or if you or your partner is pregnant, do not have sex while taking interferons. If you have autoimmune hepatitis or liver damage, do not take interferons.

In addition, interferons may make certain conditions worse. Before taking any interferon, tell your doctor if you’ve ever had any of the following:

  • Hepatitis B or C
  • HIV/AIDS
  • Any liver condition or damage
  • Any form of heart or cardiovascular disease, including high blood pressure or heart attack
  • Lung disease in any form
  • Diabetes
  • Thyroid disorders
  • Colitis
  • Cancer of any type
  • Autoimmune disorders of any form, including rheumatoid arthritis or psoriasis
  • Any blood disorder, especially one involving hemoglobin
  • Any condition that requires immunosuppressants, such as an organ transplant
  • Kidney disease
  • High triglycerides
  • Any form of drug addiction 
  • Any history of mental illness

Interferons also cause an elevated risk of autoimmune disorders, mood or behavior problems, stroke, and life-threatening infections.

Side Effects — Antiviral Interferons

Common side effects of interferons include:

  • Fever
  • Chills
  • Headache
  • Muscle and joint pain 
  • Fatigue

Drug Interactions — Antiviral Interferons

Do not take interferons with any other drug that interacts with the immune system. As interferons can have unexpected effects, carefully review any medications you take with your doctor before starting a course of interferons. It’s also recommended to discontinue any herbal supplements before starting on interferons.

Medical doctor holding a pill.

Chemokine Receptor Antagonists

Specifically used against HIV infections to slow their spread, chemokine receptor antagonists (CRAs) block the paths HIV takes to get into human cells. Currently, the only one on the market is maraviroc (Selzentry), although several others are in development. Maraviroc can be taken in pill or liquid form.

Warnings and Contraindications — Chemokine Receptor Antagonists

If you have kidney disease, there’s an elevated risk of a drug interaction with chemokine receptor antagonists. Review all medications you’re taking, including over-the-counter drugs and herbal supplements, with your doctor.

Also tell your provider if you experience any of the following:

  • Itching or rash
  • Vomiting
  • Pain in the upper abdomen or stomach
  • Darker urine
  • Jaundice

Heart disease and liver disease are also risk factors. CRAs can also compromise your immune system, so review the signs of a new and dangerous infection with your doctor.

See a doctor immediately if you’re feeling lightheaded or feel an intense pain, pressure, or tight feeling in your chest, neck, jaw, or shoulder.

Side Effects of Chemokine Receptor Antagonists

Common short term side effects include:

  • Cold-like symptoms, such as fever or cough
  • Digestive problems, including gas, bloating, nausea, vomiting, diarrhea, and constipation
  • Rash
  • Dizziness

Over the long term, there may be other rare side effects you should alert your doctor to immediately, particularly in combination. 

These include:

  • Any signs of a potentially serious infection, including: 
    • Fever 
    • Night sweats 
    • Swollen glands
    • Cold sores
    • Respiratory symptoms like coughing or wheezing
    • Diarrhea
    • Sudden weight loss
  • Trouble speaking or swallowing
  • Balance or eye movement concerns 
  • Weakness 
  • A prickly feeling
  • Swelling in your neck or throat 
  • Menstrual changes
  • Sexual dysfunction

Drug Interactions — Chemokine Receptor Antagonists

Do not take any other drug that affects the immune system with a chemokine receptor antagonist. Due to the way these medications work, they may have unexpected interactions with a wide range of drugs, so carefully review everything you take with your doctor before starting a CRA.

Reading a label.

Integrase Strand Transfer Inhibitors (ISTIs)

Integrase strand transfer inhibitors block the enzyme integrase, which retroviruses use to change the genome of cells. This limits the spread of the virus. ISTIs are largely used to manage HIV infections, although they’re currently being studied for use on other retroviruses. Common ISTIs include:

Warnings and Contraindications — ISTIs

ISTIs can affect blood glucose level, so if you have diabetes or prediabetics, consult with your provider before starting a course of ISTIs. People with liver disease shouldn’t take ISTIs. If you’re pregnant or could become pregnant, you will need to avoid ISTIs for at least the first twelve weeks of pregnancy.

Side Effects — ISTIs

Common side effects of ISTIs include:

  • Nausea
  • Diarrhea
  • Fever
  • Weight gain
  • Insomnia
  • Depression

If you have trouble or pain urinating or another sign of kidney problems, see a doctor immediately.

Drug Interactions — ISTIs

ISTIs may interact with other retrovirals to cause problems with the kidneys. ISTIs shouldn’t be taken with antiplatelet drugs such as Plavix. 

Dosages of some drugs, such as erectile dysfunction medications, antidepressants, and lipid modifier drugs, may need to be adjusted for safety as ISTIs can speed up or slow down their breakdown in the body. Review all medications with your doctor before starting a course of ISTIs.

Holding pill packet.

Neuraminidase Inhibitors (NAIs)

Neuraminidase inhibitors (NAIs) block the enzyme neuraminidase, which is used by the influenza virus to replicate. These inhibitors block both influenza A and B, unlike other flu drugs that only work against A, and can be used both to treat infections and to prevent them. Typically, three neuraminidase inhibitors are commonly distributed:

Warnings and Contraindications — Neuraminidase Inhibitors

If you are pregnant or breastfeeding, have a history of kidney disease, heart disease, liver disease, or swelling of the brain; are immunocompromised; or have a fructose allergy, tell your doctor before taking any NAIs. 

Side Effects – Neuraminidase Inhibitors

The most common side effects of NAIs include:

  • Vomiting
  • Stomach pain
  • Nosebleeds
  • Headache
  • Fatigue 

Drug Interactions — Neuraminidase Inhibitors

If you’ve had a nasal flu vaccine, you’ll need to avoid NAIs until cleared by your doctor, usually 48 hours after receiving the vaccine.

As of this writing, there are no documented common interactions between NAIs and other commonly prescribed medications. Always check with your doctor whenever you start a new medication to confirm that none have been found.

Taking a pill.

Non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs)

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are used to treat HIV and occasionally hepatitis B. They limit the ability of reverse transcriptase to function, which HIV needs to replicate itself.

NNRTIs in common usage include:

Warnings and Contraindications — NNRTIs

If you have liver problems or complications, review them with your doctors before beginning NNRTIs. In rare cases, they can interfere with the metabolization of other drugs.

Side Effects — NNRTIs

Common side effects of NNRTIs include:

  • Headache
  • Dizziness
  • Insomnia
  • Depression
  • Nausea and vomiting
  • Fatigue
  • Abdominal pain
  • Rash

Skin hypersensitivity has been noted In extremely rare cases.

Drug Interactions — NNRTIs

There are currently no reported major drug interactions with NNRTIs, but review everything you take, including over-the-counter medication and herbal supplements, with your doctor before starting NNRTIs.

scientists using a microscope

Nonstructural protein 5A (NS5A) Inhibitors

Currently used to treat hepatitis C, nonstructural protein 5A inhibitors (NS5A inhibitors) target a specific protein the hepatitis virus uses in its reproductive cycle. Currently, the only NS5A inhibitor on the market is daclatasvir, marketed under the name Daklinza.

Warnings and Contraindications — NS5A Inhibitors

If you have heart disease or liver disease, review your condition with your doctor before taking NS5A inhibitors. If you’ve previously had hepatitis B, it may re-emerge when taking NS5A inhibitors.

Side Effects — NS5A Inhibitors

Headache and nausea are the most common side effects. Some patients report diarrhea.

Drug Interactions — NS5A Inhibitors

Most common drugs can be taken with NS5A inhibitors, but a few classes, such as antiseizure medication and some cancer treatments, may cause  negative interactions. 

Woman sleeping on a couch.

Nucleoside Reverse Transcriptase Inhibitors (NRTIs)

Nucleoside reverse transcriptase inhibitors (NRTIs) limit viral replication by competing with viruses for the cellular triphosphates viruses need to reproduce. Mostly used to treat HIV, NRTIs were among the first antivirals developed to fight retroviruses. 

The NRTIs currently on the market include:

Warnings and Contraindications — NRTIs

If you have liver disease, kidney disease, bone density concerns, or an organ transplant, tell your doctor before taking any NRTIs. Some NRTIs may affect your immune system, so you’ll need to monitor your health for signs of new infections.

Side Effects — NRTIs

The most common side effects of NRTIs include:

  • Fever
  • Headache
  • Gastrointestinal symptoms including stomach pain, nausea, vomiting, and diarrhea
  • Rash and itching
  • Dizziness or weakness
  • Insomnia
  • Mild depression

Drug Interactions— NRTIs

NRTIs should generally not be taken with other antivirals unless prescribed by a doctor. NRTIs may interact with drugs that treat osteoporosis, arthritis, high blood pressure, and cancer, so review any medications you already take with your provider before starting a course of NRTIs.

Medical doctor holding medication.

Protease Inhibitors

Used to treat HIV and hepatitis C, protease inhibitors block the enzyme protease from splitting certain proteins into smaller fragments. Currently available protease inhibitors include:

Warnings and Contraindications – Protease Inhibitors

Protease inhibitors may harm an unborn baby, so if you could become pregnant, usage should be carefully monitored by your doctor. If you’re in a household with a high risk of infection, protease inhibitors may elevate your risk of serious problems from other microbes. Protease inhibitors will not prevent you from infecting others with hepatitis C. 

Side Effects — Protease Inhibitors

If you experience any side effects, you should contact a doctor immediately. In particular, monitor your health for the following:

  • Black or tar-like stools
  • Bleeding or signs of bleeding, including around the gums and in the urine or stool
  • Unusual bruising
  • Chills
  • Cough
  • Fever
  • Pain, stiffness, or swelling of the joints
  • Unusual pain in the stomach, back, or side
  • Difficulty or pain urinating
  • Loss of skin color
  • Rash or pinpoints on the skin
  • Difficulty breathing
  • Sore throat
  • Swelling of the feet or lower legs
  • Ulcers, sores, or white spots in the mouth
  • Fatigue

Drug Interactions — Protease Inhibitors

Because of their mechanism of action, there is a wide range of drugs that should not be used with protease inhibitors. Dosages need to be adjusted for others. In particular, pain management medication, erectile dysfunction medication, and ergot-based drugs may cause serious medical issues and should be avoided. Protease inhibitors can also interfere with contraceptives.

medical doctor holding medication

Purine Nucleosides

This class of drugs is used to limit the outbreak of herpes simplex viruses like genital herpes and chickenpox. They work by inhibiting the virus’ DNA polymerase and ending its growth chain. 

Drugs in this class are fairly common and include: 

Warnings and Contraindications — Purine Nucleosides

You should not take purine nucleosides if you have HIV/AIDS or kidney disease. Their effect on pregnancy is still unclear, and you should consult with your obstetrician if you become pregnant while taking a drug in this class to prevent herpes infections.

Side Effects — Purine Nucleosides

Common side effects of purine nucleosides include nausea, stomach pain, and headaches. 

If you experience any of the following reactions, contact a doctor immediately.

  • Confusion
  • Aggression
  • Hallucinations 
  • Speech issues
  • Seizures
  • Kidney problems
  • Fever
  • Pallid skin
  • Nosebleeds
  • Bleeding gums
  • Blood in the urine or stool
  • Unrelated red spots on the skin
  • Fatigue
  • Stomach pain
  • Vomiting
  • Swelling in the extremities

Drug Interactions — Purine Nucleosides

Purine nucleosides can affect any drug that’s metabolized in the kidneys. These medications include:

  • Other antivirals
  • Immunosuppressants
  • Blood pressure medications
  • Some arthritis medicines
Family looking at wild flowers.

Find the Best Prices for Antiviral Medications with BidRx

Antivirals can help you fight off dangerous infections and get more out of life. BidRx puts your prescription out to a wide range of pharmacies to compete for your business, helping you find the best price for antiviral medications.

How BidRx Works 

Once you’ve signed up on the BidRX portal, you can quickly and easily create a bid for the prescription you need, and pharmacies will respond with their best offers. You then select from the bids, and they fill your order.
Pharmacies bidding include specialty pharmacies, local businesses, mail-order facilities, and more, so you can choose where your business goes. Compare prices online and get the best price for antivirals with BidRx.

The BidRx team is a group of professional medical and healthcare writers

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