Anti-viral agents

Question 1

What is the selectivity of action of aciclovir

Answer 1

only activated in infected cells, then becomes concentrated

has a higher affinity for viral DNA polymerase than cellular enzymes`

Question 2

What enzyme activates aciclovir?

Answer 2

thymidine kinase

Question 3

What is aciclovir competitive with, what does it do?

Answer 3

Competes with GTP
Inhibits viral DNA polymerase, DNA chain terminator

has a narrow spectrum of activity

Question 4

There is resistance to aciclovir, but these are non-pathogenic. How are they resistant?

Also appears in less harmful viruses, how?

Also appears in harmful viruses, how?

Answer 4

Absence of thymidine kinase

Mutant form of thymidine kinase

Altered DNA polymerase

Question 5

What is the prophylaxis treatment for genital herpes

Answer 5

aciclovir
patient can titrate dose
cessation leads to pre-therapy state
leads to long term therapy

Question 6

An anti-cytomegalovirus drug example is ganciclovir

what does it require
what does it do
what is it active against
disadvantages

Answer 6

requires phosphorylation by UL97

ganciclovir triphosphate acts as DNA pol inhibitor

active against all herpesviruses

poor oral absorption - valganciclovir
toxic to bone marrow.

Question 7

Another example of an anti-cytomegalovirus is cidofovir

what does it require
what does it do
what is it active against
disadvantages

Answer 7

Non-viral dependent phosphorylation

Inhibits viral DNA polymerase
Broad spectrum

given by IV
nephrotoxic

Question 8

The last example of an anti-cytomegalovirus drug is foscarnet

what does it do
disadvantages

Answer 8

viral DNA polymerase inhibitor

poor oral availability
nephrotoxic

Question 9

Ribavirin may interfere with mRNA processing and acts a mutagen. It is broad spectrum; both DNA and RNA viruses, but it is only useful in what scenarios

Answer 9

Severe RSV infection - inhale drug
Lassa fever
Chronic hep C virus infection

Question 10

Amantadine inhibits uncoating of influenza A virus, but is no longer recommended, why?

Answer 10

Poorly tolerated bc of CNS stimulation

resistance rapidly emerges

Question 11

Neuraminidase inhibitors, work against all known influenza NA (for severe/high risk). name the two examples

Answer 11

zanamavir and

oseltamivir (resistance reported)