Patient Rights Treatment Decisions & Safety Brief Guide to Antiviral Drugs By Naveed Saleh, MD, MS Naveed Saleh, MD, MS LinkedIn Twitter Naveed Saleh, MD, MS, is a medical writer and editor covering new treatments and trending health news. Learn about our editorial process Updated on April 06, 2022 Medically reviewed by Violetta Shamilova, PharmD Medically reviewed by Violetta Shamilova, PharmD Violetta Shamilova, PharmD, is a board-certified pharmacist and assistant professor at Touro College in New York. Learn about our Medical Expert Board Print HIV Particles. BSIP/UIG/Getty Images Viruses are intracellular parasites that co-opt cell machinery to reproduce. During reproduction, viruses destroy cells and go on to infect other cells. During the 1950s, while researching possible treatments for cancer, scientists discovered chemical compounds that could inhibit viral DNA replication. During the 1980s and 1990s, after HIV became a problem, antiviral medications experienced a renaissance. Today, antiviral medications are used to treat many diseases. In order to be effective, antiviral medications must target either viral entry or exit or screw with the virus while it's inside a cell. Antiviral medications must also be specific so as not to cause systemic toxicity. Furthermore, antiviral drugs should be potent and stable. Here are brief descriptions of some of the antiviral drugs currently available. Antiviral Drugs Used to Treat Herpes Simplex Virus (Hsv) and Varicella-Zoster Virus (Vzv) The three main drugs used to treat herpes simplex (herpes) and varicella zoster viruses are acyclovir, valacyclovir, and famciclovir. Varicella zoster virus causes both chicken pox after acute infection and shingles (herpes zoster) after latent or reactivated infection. All 3 of these drugs are relatively safe and have similar mechanisms of action. For instance, they all work by binding to viral DNA polymerase, an enzyme used to replicate viral DNA. Of note, because valacyclovir (Valtrex) and famciclovir reach higher blood concentrations, these 2 drugs are most effective in treating shingles. Drugs Used to Treat Genital Warts (Human Papillomavirus) Drugs used to treat genital warts include: Ribavirin which is also used to treat respiratory syncytial virus (RSV) bronchiolitis or pneumonia and (less frequently) influenza (Topical) imiquimod Antiviral Drugs Used to Treat Influenza (The Flu) Influenza is a common cause of flu during the winter season. Fortunately, we have vaccines that confer immunity to the seasonal flu. It's important to obtain your yearly flu shot because sometimes flu can become pneumonia, and sometimes pneumonia can kill--especially among children and older people. Drugs like Tamiflu (oseltamivir) and zanamivir (Relenza) can be used to prevent symptoms of the flu and shorten the length of illness. In addition to drugs used to prevent influenza disease or pathology, there are also drugs which mess with viral machinery after infection with influenza including amantadine, rimantadine, oseltamivir, and zanamivir, Antiviral Drugs Used to Treat Cytomegalovirus (Cmv) Infections Cytomegalovirus infection typically occurs in people who are very sick (think immunocompromised by AIDS or organ transplant). Like the varicella-zoster virus, which causes herpes zoster (shingles), most of us harbor the cytomegalovirus, but the virus will only reactivate if you're immune system is run down. In those who are already pretty sick, symptoms of cytomegalovirus infection affect many organ systems and include: RetinitisEsophagitisColitisBrain and spinal cord (CNS) infectionPneumonitis Drugs used to treat cytomegalovirus infection include valganciclovir, ganciclovir, foscarnet, and cidofovir. (Because of greater bioavailability, use of valganciclovir has largely replaced ganciclovir.) Like other antiviral drugs, antiviral drugs used to treat cytomegalovirus in part mess with viral enzymes like viral DNA and RNA polymerase. Antiviral Drugs Used to Treat Hepatitis Various antiviral drugs are used to treat hepatitis B and hepatitis C. Most of these drugs directly affects viral reproduction including: Nucleoside and nucleotide analogsProtease inhibitorsPolymerase inhibitors Interferon, probably the most common drug associated with the treatment of hepatitis infection, works by complex mechanisms that encompass antiviral, immunomodulatory, and antiproliferative actions. Antiviral Drugs Used to Treat HIV During the past 3 decades, there have been great improvements in the treatment of HIV infection, and more people with the disease are living AIDS-free. (AIDS is a more severe form of HIV infection diagnosed after the level of white blood cells in the blood drops dangerously low.) There are several types of antiretroviral drugs: Protease inhibitorsFusion inhibitorsNucleoside/nucleotide reverse transcriptase inhibitorsNon-nucleoside reverse transcriptase inhibitorsEntry inhibitorsHIV integrase strand transfer inhibitors (INSTIs) These drugs target various stages of the viral replication cycle. Of note, retroviruses replicate by means of reverse transcription. Please note that this list is by no means comprehensive, and there are several other drugs that treat viral infections. Of equal note, mechanisms of action are far more complicated than presented here. Instead, please appreciate this article as a primer on the topic. Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Elston DM. Chapter 231. Antiviral Drugs. In: Goldsmith LA, Katz SI, Gilchrest BA, Paller AS, Leffell DJ, Wolff K. eds. Fitzpatrick's Dermatology in General Medicine, 8e. New York, NY: McGraw-Hill; 2012. Accessed July 01, 2015. Safrin S. Antiviral Agents. In: Katzung BG, Trevor AJ. eds. Basic & Clinical Pharmacology, 13e. New York, NY: McGraw-Hill; 2015 Accessed July 01, 2015. Selected Sources By Naveed Saleh, MD, MS Naveed Saleh, MD, MS, is a medical writer and editor covering new treatments and trending health news. See Our Editorial Process Meet Our Medical Expert Board Share Feedback Was this page helpful? Thanks for your feedback! What is your feedback? Other Helpful Report an Error Submit