Antivirals Flashcards
How does acyclovir act
Purine analogue that is activated ( through phosphorylation) by viral thymidine kinase
Competes with GTP and inhibits viral DNA polymerase as is a chain terminator
What is acyclovir active against
Herpes virus family only HSV1 HSV2 and VZV
What are the reasons for acyclovir resistance
Absence of thymidine kinase ( usually non-pathogenic)
Alteration of thymidine kinase ( attenuated virulence)
Altered DNA polymerase - big problem
What is used for oral absorption of acyclovir
Valine ester- valaciclovir
When would you use acyclovir for genital herpes
If the infection was severe, frequent or atypical
What are the complications of herpes
Corneal kerititis leads to blindness, contact transmission from mouth
Eczema herpeticum- disseminates into internal organs
Encephalitis I
What is an anti CMV drug
Ganciclovir
Cidofovir
Foscarnet
How does ganciclovir work
Acyclic guanosine analogue
Requires phosphorylation by UL97
DNA pol inhibitor
What is good and bad about ganciclovir
Active against all herpes viruses
Poorly orally absorbed need valine ester
Toxic to bone marrow
When is VZV a problem
Adult forms can cause pneumonia
In pregnancy can also get pneumonia
What is shingles
Reactivated VZV
Lies latent in spinal cord and cranial nerves
Can cause zoster kernititis
What is cidofovir
Acyclic phosphonate nucleotide analogue
Not dependant on view phosphorylation
Broad spectrum
What is the problem with cidofovir
It is nephrotoxic but used in eye drops against CMV retinitis
What is foscarnet
Pyrophosphate analogue
viral DNA polymerase inhibitor
What’s the problem with foscarnet
Nephrotoxic
How is acyclovir selective
Only activated in infected cells
Becomes more concern tested in infected cells due to concentration gradient
Higher affinity for viral DNA polymerase than cellular enzymes
What is ribavirin
Broad spectrum not sure how it acts mRNA? Mutagen?
Only useful in vitro or for sever RSV infection in neonate a- give inhalation
Or chronic hep C give with an interferon
What is amatadine
Inhibits the uncoating of influenza a so stops it being released?
CNS stimulation means it’s no longer recommended
What are neuraminidase inhibitors
Zanamavir and oseltamivir
Work against all know flu NA, leads to the virion getting stuck of the surface of the cell membrane so cannot move away from cell
