They kill viruses or inhibit viral growth.
| Antiviral | Mechanism of action | Use | Adverse effect |
| Drugs used in the treatment of influenza | |||
| Amantadine | Interferes with uncoating of viral RNA by blocking the M2 ion channel | Influenza A (widespread resistance common); Parkinson’s disease | Insomnia, seizures, anorexia |
| Oseltamivir (Tamiflu) | Prodrug activated by esterases; inhibits viral neuraminidase, which inhibits the release of virus particles from host cells | Influenza A and B; decreases the severity and duration of symptoms if taken within 48 hours of symptom onset | Bronchitis, insomnia, nausea, vertigo, vomiting |
| Zanamivir (relenza) | Inhibits viral neuraminidase, which inhibits the release of virus particles from host cells | Influenza A and B; administered by inhalation; use within 48 hours | Bronchospasm, nasal and throat discomfort |
| Rapivab (peramivir) | Inhibits viral neuraminidase, which inhibits the release of virus particles from host cells | Influenza A and B; given by intravenous infusion; use within 48 hours | Diarrhea, neutropenia, elevated glucose, elevated liver enzymes, hypersensitivity |
| Xofluza or baloxavir | Prodrug; baloxavir inhibits the endonuclease activity of the PA protein, which inhibits viral replication | Influenza A and B; use within 48 hours of symptom onset | Diarrhea, nausea, headache, nasopharyngitis, bronchitis |
| Drugs used in the treatment of HSV, VZV and CMV | |||
| Acyclovir | Guanosine analogue that is acted on by viral thymidine kinase and then further activated by human enzymes to an active form that inhibits viral DNA polymerase | Herpes zoster, genital herpes, HSV encephalitis, and VZV (varicella zoster) | Phlebitis, nausea, headache, malaise, renal insufficiency, encephalopathy; probenecid delays the elimination of acyclovir |
| Valacyclovir | Prodrug converted in the body to acyclovir; the rest of the action is the same as acyclovir | Herpes zoster, genital herpes, herpes labialis | TTP, HUS, renal insufficiency |
| Ganciclovir | Activated by viral thymidine kinase and then further activated by human enzymes to an active form that inhibits viral DNA polymerase. In CMV infections, Ganciclovir is activated by a viral kinase known as UL 97 kinase. | CMV retinitis | Myelosuppression, CNS toxicity, teratogenicity, pancreatitis |
| Valganciclovir | Prodrug of ganciclovir; same mechanism as ganciclovir | CMV retinitis | Myelosuppression, CNS toxicity, teratogenicity, pancreatitis |
| Foscarnet | An inorganic pyrophosphate that competes with viral enzymes for the binding site and inhibits them. Enzymes inhibited include viral DNA polymerase, RNA polymerase, and HIV reverse transcriptase. | Immunocompromised patients with CMV retinitis; mucocutaneous HSV infections; acyclovir-resistant HSV and VZV infections | Renal insufficiency, seizures, electrolyte imbalance, nausea, headache, diarrhea, hematologic disturbances |
| Cidofovir | Nucleotide analogue that inhibits viral DNA polymerase | CMV retinitis in AIDS, HSV | Nephrotoxicity, neutropenia, thrombocytopenia |
| Drugs used in the treatment of hepatitis viruses and Ribavirin | |||
| Ribavirin | Riboside analogue converted to a triphosphate form that inhibits viral RNA polymerase and inhibits capping of viral mRNA. It also inhibits viral inosine monophosphate dehydrogenase in HCV and inhibits viral replication. | RSV, HCV | Respiratory distress, hemolytic anemia, cough, pruritus, rash; contraindicated in pregnancy due to teratogenicity |
| Palivizumab | Humanized monoclonal antibody against the F glycoprotein of RSV; prevents viral invasion of host cells | Used for prophylaxis of RSV in high-risk infants (e.g., chronic lung disease, congenital heart disease, immunodeficiencies); it cannot treat RSV infection | Local erythema, pain, fever, rash; rarely anaphylaxis |
| Adefovir | Blocks HBV reverse transcriptase | Chronic HBV | Asthenia, nephrotoxicity, elevated liver enzymes, headache, nausea, lactic acidosis, liver failure, fatty liver; may develop resistance to HIV drugs (RTIs) |
| Entecavir | Guanosine analogue that blocks HBV polymerase | Chronic HBV | Hepatotoxicity, elevated liver enzymes, fatty liver, lactic acidosis; may develop resistance to HIV RTIs |
| Pegylated Interferon alpha-2a and 2b | Binds to and activates human type 1 interferon receptors on hepatocytes, activating intracellular signal transduction pathways that increase gene expression and inhibit viral replication. It augments host antiviral responses, degrades viral mRNA by activating ribonucleases, and blocks protein synthesis by inhibiting translation and initiation complex formation. | HBV and HCV, RSV, Kaposi’s sarcoma in AIDS, and malignant melanoma; newer and safer drugs are preferred over peg IF alpha | Flu-like symptoms, arrhythmias, tachycardia, cardiomyopathy, thyroid dysfunction, hepatotoxicity, photosensitivity, myelosuppression, depression, renal insufficiency |
| Sofosbuvir | Prodrug converted by hepatic cellular kinases to an active form; uridine nucleotide analogue that inhibits HCV polymerase and therefore inhibits viral replication | Chronic HCV; increases the duration of therapy needed for genotype 3 of HCV | Fatigue, headache, severe bradycardia with amiodarone or beta blockers |
| Velpatasavir | Inhibitor of NS5A protein; viral replication complex inhibitor | Chronic HCV | Headache, fatigue |
| Ledipasvir | Inhibits the HCV NS5A protein, which plays a role in viral replication, assembly, and release | Chronic HCV | Fatigue, headache; caution when prescribed with cyt P450 inducers, as they decrease drug levels and can cause treatment failure |
| Grazoprevir | HCV protease inhibitor; inhibits viral replication | Chronic HCV | Hepatotoxicity, diarrhea, headache |
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