antiviral agnets against Herpes

Acyclovir / Valacyclovir / Penciclovir / Famciclovir

• Mechanism of Action: Guanosine analogue activated by HSV/VZV-coded thymidine kinase; inhibits viral DNA polymerase via chain termination.

• Indications: Active infections (HSV encephalitis, genital herpes, shingles), prophylaxis in recurrent or severe infections. Not effective against latent infections or CMV.

• Adverse Effects: Obstructive crystal-induced nephropathy, acute kidney injury, thrombotic thrombocytopenic purpura, gastrointestinal symptoms, elevated transaminases.

• Resistance Mechanism: Mutation of viral thymidine kinase.

Ganciclovir / Valganciclovir

• Mechanism of Action: Guanosine analogue activated by CMV-coded UL97 kinase; inhibits viral DNA polymerase.

• Indications: CMV retinitis in immunocompromised patients, CMV prophylaxis in transplant recipients.

• Adverse Effects: Myelotoxicity (pancytopenia), nephrotoxicity, gastrointestinal symptoms, CNS effects (headache, confusion, paresthesias).

• Resistance Mechanism: Mutation of viral UL97 kinase.

Foscarnet

• Mechanism of Action: Pyrophosphate analogue; inhibits DNA/RNA polymerase and HIV reverse transcriptase.

• Indications: Ganciclovir-resistant CMV retinitis, acyclovir-resistant HSV.

• Adverse Effects: Nephrotoxicity, gastrointestinal symptoms, CNS effects (headache, confusion, seizures), electrolyte abnormalities, hematological abnormalities.

• Resistance Mechanism: Mutation of viral DNA polymerase.

Cidofovir

• Mechanism of Action: Viral DNA polymerase inhibitor; direct inhibition without viral kinase activation.

• Indications: CMV retinitis, acyclovir-resistant HSV.

• Adverse Effects: Nephrotoxicity (mitigated with probenecid and IV fluids).

Fomivirsen

• Mechanism of Action: Antisense antiviral blocking viral mRNA translation.

• Indications: Local treatment of CMV retinitis in AIDS patients (via intraocular injection).

• Adverse Effects: Eye infections, increased intraocular pressure, macular edema.

• Resistance Mechanism: Unknown.