Table 2.

Key antiviral drugs, their mechanisms of action, and toxicities

Drug	Mechanism of Action	Key Toxicities
Ganciclovir94	Acyclic nucleoside analog of guanosine, undergoes triphosphorylation and then targets the viral DNA polymerase to inhibit viral DNA synthesis by competitively inhibiting incorporation of dGTP into DNA	Cytopenias Renal dysfunction
Valganciclovir95	Prodrug of ganciclovir, rapidly converted to ganciclovir by intestinal and hepatic enzymes after oral administration	Cytopenias Renal dysfunction
Foscarnet	Pyrophosphate analog, directly inhibits CMV DNA replication by binding to the DNA polymerase	Renal dysfunction Electrolyte wasting
Cidofovir	Monophosphate nucleotide analog, phosphorylated to its diphosphate form and then inhibits the viral DNA polymerase by competitively inhibiting incorporation of dCTP into DNA	Renal dysfunction
Letermovir	Inhibits CMV viral terminase complex, preventing packaging of DNA before encapsidation of viral genome	Gastrointestinal symptoms
Maribavir	Inhibits phosphorylation of nuclear lamins by UL97 kinase, preventing formation of viral capsid and nuclear egress of viral particles; also impacts viral gene expression and DNA synthesis	Dysgeusia Nausea and vomiting
Acyclovir96	Acyclic guanosine analog, undergoes triphosphorylation and then targets the viral DNA polymerase to inhibit viral DNA synthesis by competitively inhibiting incorporation of dGTP into DNA	Renal dysfunction Anemia Neutropenia Nausea and vomiting Rare neurologic toxicity
Valacyclovir97	Prodrug of acyclovir; after oral administration, rapidly converted to acyclovir via first-pass intestinal and hepatic metabolism	Headache Nausea and vomiting Acute renal failure Thrombotic thrombocytopenic purpura/Hemolytic uremic syndrome
Oseltamivir	Competitive inhibitor of influenza neuraminidase, preventing release of new virions	Nausea and vomiting
Baloxavir	Cap-endonuclease inhibitor, inhibits endonuclease subdomain of the viral RNA polymerase, preventing transcription of viral mRNA	Diarrhea
Peramivir	Competitive inhibitor of influenza neuraminidase, preventing release of new virions
Zanamivir	Competitive inhibitor of influenza neuraminidase, preventing release of new virions	Cough Sore throat
Ribavirin	Guanosine analog, multiple mechanisms of action have been proposed, including inhibition of the viral polymerase of RNA viruses	Hemolytic anemia