Antivirals

Question 1

What are the strategies of antiviral drugs?

Answer 1

Target points in viral replication cycle

• immunoglobulins - target attachment
• amantidine - target uncoating
• Aciclovir, Ganciclovir, Foscamet - target replication
• Oseltamivir - targets release

Question 2

What is Aciclovir used for?

Answer 2

Herpes simplex (oral/genital ulcers)
Varicella zoster (chickenpox/shingles)

Question 3

What is the mechanism of action of Aciclovir?

Answer 3

Metabolised by viral enzymes in infected cells into active form
- only becomes active in infected cell, limits SEs

Terminates DNA chain formation by mimicking guanosine
- becomes incorporated into DNA, but won’t attach next base

Question 4

What is Ganciclovir used against?

Answer 4

CMV (only in v.dangerous infection, i.e. sight/life)

Question 5

What is the mechanism of action of Ganciclovir?

Answer 5

Similar to Acivlovir but activated in non-infected cells also

Question 6

What are the side effects of Ganciclovir?

Answer 6

Widespread and unpleasant SEs

• affect blood cell prduction, therefore 1% experience:
  
  • > neutropenia
  • > thrombosytopenia
  • > granulocytopenia
  • > anaemia

Question 7

What is Oseltamivir (Tamiflu) used against?

Answer 7

Influenza - only in high risk or pandemics

Question 8

What is the mechanism of action of Oseltamivir (Tamiflu)?

Answer 8

Inhibits neuraminidase (protein required to cause membrane budding and virus release)

Question 9

What are the side effects of Oseltamivir (Tamiflu)?

Answer 9

affect 40-50%

• N&V
• Abdominal pain
• Headache

Question 10

What form does Oseltamivir (Tamiflu) come in?

Answer 10

Tablet form

Inhaled form: Zantamivir (Relenza)

Question 11

How effective is Oseltamivir (Tamiflu)?

Answer 11

Relieves duration and severity of flue by ~ 30%

Must be used <48 hours of symptom onset (after this not effective)