Antiviral drugs

Amantadine

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.

 

Famcyclovir

 

 

gancyclovir

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.

 

 

foscarnet

inhibitory for all herpesviruses

pyrophosphate analog

toxicity is a subsantial problem; avoid if possible