Antivirals | Antimicrobials | Pharmacology

They kill or inhibit the growth of viruses.

Important antivirals

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, inhibition of 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)	inhibition of 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)	inhibition of viral neuraminidase which inhibits the release of virus particles from host cells	Influenza A and B, 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 PA protein and 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 upon by viral thymidine kinase and further activated by human enzymes to the 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, rest action same as acyclovir	Herpes zoster, genital herpes, herpes labialis	TTP, HUS, renal insufficiency
Ganciclovir	Activated by viral thymidine kinase and further activated by human enzymes to the active form that inhibits viral DNA polymerase	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 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 F glycoprotein of RSV, prevents viral invasion of host cells	Used for prophylaxis of RSV in high risk infants like those with chronic lung disease, congenital heart disease and 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 which activates intracellular signal transduction pathways that increase gene expression leading to the inhibition of viral replication, augments host antiviral responses, degrades viral mRNA by activating ribonucleases, blocks protein synthesis by inhibition of 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 active form; uridine nucleotide analogue, inhibitor of HCV polymerase thus inhibits viral replication	Chronic HCV, increase 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	Inhibitor of viral HCV NS5A, that plays a role in viral replication, assembly and release	Chronic HCV	Fatigue, headache; Caution when prescribed with cyt P450 inducers as it decreases drug levels causing treatment failure
Grazoprevir	HCV protease inhibitor, inhibits viral replication	Chronic HCV	Hepatotoxicity, diarrhea, headache