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Antiviral drugs

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Antiviral drugs target specific virus molecules and mechanisms.

acyclovir - HSV, VSV


  • amantadine
  • neuramindase inhibitors
  • herpes family inhibitors


M2 ion channel inhibitor, blocking viral uncoating and RNA transscription. Influenza A only

Prophylaxis. 60-70% effective in preventing infection in institutionalized

Side effects: agitation, confusion, loss of balance, nausea and vomiting

Increased resistance among many Influenza

Neuraminidase Inhibitors

Oseltamavir (Tamiflu)

High-affinity for active site of NA, preventing spread of virus particles from cell to cell

Active against influenza A and B. Effective against all strains, though resistance is an increasing issue.

Herpes Family Inhibitors


acyclovir, valcyclovir,

  • activated (only) by viral thymidine kinase
  • accumulates in infected host cells
  • inhibits viral DNA synthesis by competitive inhibition and chain termination
  • better bioavailability than acyclovir
  • if urine is too concentrated, excreted acyclovir crystalizes,


excreted in urine



Mono-phosphorylated by thymadine kinases to inhibit viral DNA polymerase.

Acyclovir: low oral bioavailability.

Side effects: worse with IV use.

appears to be safe in pregnancy

Resistance (thymadine kinase mutations) increasing in patients with AIDS, or transplant patients.






developed to target CMV

  • Ganciclovir is structurally similar to ACV but is more toxic.
  • used to treat severe CMV infections in immunocompromised patients.
  • It is activated by viral enzymes and inhibits viral DNA polymerase, causing DNA chain termination.




inhibitory for all herpesviruses

pyrophosphate analog

toxicity is a subsantial problem; avoid if possible