Anti-virals

Question 1

Look

Answer 1

• All anti-virals are virustatic, none are virucidal
• They target several stages of the virus life cycle

Question 2

What is the most common type of anti-viral?

Answer 2

Nucleoside analogues - These inhibit nucleic acid synthesis

Question 3

In which situations might anti-viral treatment be given? (4)

Answer 3

• Prophylaxis - to prevent infection
• Pre-emptive therapy - when evidence of infection detected, but before symptoms apparent
• Overt disease - clinically obvious, symptomatic
• Suppressive therapy - to keep viral replication below the rate that causes tissue damage in asymptomatic infected patient

Question 4

Which anti-virals are commonly used to fight overt disease?

Answer 4

Aciclovir or Oseltamivir

Question 5

Which anti-virals are commonly given pre-emptively?

Answer 5

Interferon/Ribavirin for HCV

Question 6

Which drug is given as prophylactic treatment for Herpes infection?

Answer 6

Aciclovir

• However, anti-virals cannot eradicate the virus from latently infected cells so after an episode of overt infection, suppressive (maintenance) treatment may be needed

Question 7

Which anti-viral is used in practice for HIV, Hep B and Hep C?

Answer 7

Tenofovir

Question 8

Which anti-virals are used in practice for influenza A or B?

Answer 8

• Oseltamivir
• Zanamivir

Both have a role in treatment and prophylaxis, however, they are not always indicated, but if used, should usually start within 48 hours of onset of symptoms/contact.

Question 9

Which patients are given anti-virals for chickenpox?

Answer 9

Those at increased risk of complications i.e neonates, immunocompromised or pregnant women

Question 10

Which drugs are given for Herpes simplex and varicella zoster viruses?

Answer 10

• Aciclovir
• Valaciclovir
• Famciclovir
• Foscarnet

Question 11

Describe Aciclovir’s (the most widely used antiviral agent) mode of action

Answer 11

1. Aciclovir is first converted by viral thymidine kinase to ACVMP
2. ACVMP then converted by host cell kinases to ACV-TP
3. ACV-TP, in turn, competitively inhibits and inactivates HSV-specific DNA polymerase
4. Preventing further viral DNA synthesis without affecting the normal cellular processes

Question 12

When would Anti-virals be used for Cytomegalovirus (CMV)?

Answer 12

Only used in life-threatening or sight-threatening CMV infections i.e

• HIV patients with…
  
  • CMV retinitis
  • Colitis
• Transplant recipients with…
  
  • Pneumonitis
• May also be used to treat neonates with symptomatic congenital CMV infection

Question 13

Which anti-virals are used to treat CMV?

Answer 13

• Aciclovir
• Ganciclovir
• Valganciclovir
• Cidofovir
• Foscarnet if resistant to aciclovir (different site of action)

Question 14

Anti-virals used for chronic hep B infection

Answer 14

• Pegylated interferon alpha (subcut.)
• Nucleoside/tide analogues
  
  • Tenofovir
  • Adefovir
  • Entecavir

Question 15

Anti-virals used for chronic hep C infection

Answer 15

• Pegylated interferon alpha (subcut.) & ribavirin (oral)
• As above, PLUS protease inhibitor (telaprevir or boceprevir)
• New directly-acting antivirals, in combination
  • Daclatasvir
  • Sofosbuvir

Question 16

When should you suspect drug resistance to herpes virus in immunocompromised patients?

Answer 16

If there is no response to appropriate anti-viral doses within 7 days.