L23 Antivirals

Question 1

Give an example of pre-exposure prophylaxis in premature infants.
(Disease + Drug)

Answer 1

Palivizumab for RSV prophylaxis

Question 2

Give 2 examples of post-exposure prophylaxis.

Disease + Drug

Answer 2

1. HIV - Truvada = tenofovir + emtricitabine (sexual exposure, needle stick injury)
2. Influenza - Oseltamivir = Tamiflu

Question 3

What is given for chronic HBV and HCV respectively?

Answer 3

HBV: Entecavir
HCV: Ribavirin

Question 4

Give an example for prophylaxis against reactivation of latent infection.

(Disease + Drug)

Answer 4

Acyclovir for maintenance therapy for recurrent genital herpes

(also famciclovir/valaciclovir)

Question 5

Amantidine - drug class and MOA? 
It is no longer used for influenza. Why?

Answer 5

M2 ion channel blockers (M2 ion channels allow correct electrolyte flow, right pH for virus)

MOA
Inhibit uncoating

Not used

1. CNS side effects: insomnia, drowsiness (originally for Parkinson’s)
2. Resistance emerges after a few days

Question 6

What is the drug class for Acyclovir ? 
What is its MOA?

Answer 6

DNA polymerase inhibitor

MOA
- Prodrug converted to active form via phosphorylation, only by virus-encoded thymidine kinase (not other cellular kinase)

• inhibit DNA polymerase > chain termination of viral DNA synthesis

Question 7

Which of the following regarding Acyclovir is incorrect?
A. IV form can be given in severe HSV infection, e.g. HSE (encephalitis), neonatal herpes

B. Acyclovir PO for genital herpes or severe orofacial herpes

C. Eye ointment given to ophthalmic herpes

D. Cream for recurrent herpes labialis

E. Valacyclovir and Famciclovir has lower bioavailability

Answer 7

E
- higher, c.f. Acyclovir 20% only

Ganciclovir is better for CMV, but higher toxicity

Foscarnet and Cidofovir is for resistant infection, but higher toxicity

Question 8

What is the drug class od Oseltamivir and Zanamivir?

They are treatment for?

Answer 8

Neuraminidase inhibitors
- block vision release from infected cells

• Treatment for PEP (post-exposure prophylaxis) for influenza

Question 9

What are the adv and disadvantages of virus-specific Ab antivirals?

Answer 9

Adv
- immediate protection (esp for post-exposure prophylaxis)

Disadv

• short duration of protection
• Cautions: HSR, immune complex formation, blood-borne pathogens

Question 10

Which of the following about virus-specific Ab are correct?

A. Human normal Ig (HNIG) can be given to prevent common viruses like measles and HAV

B. HBIG can be given after sharps injury of vaccine non-responders, newborns of HBV+ve mothers

C. HRIG is for rabies exposure

D. VZIG is given in chickenpox exposure in pregnant women, infant and immunocompromized

E. RSV IVIG is given to high-risk infants

F. CMV IVIG is given to all patients with CMV infection

Answer 10

Only F is incorrect
CMV pneumonitis in transplant recipients

*all PEP (post-exposure prophylaxis) in vaccine naive/non-responders

Question 11

MOA of interferons?
Clinical use?

Side effects: fatigue, fever, alopecia, depression

Answer 11

Immunomodulation + antiviral

Clinical use
- HBV, HCV, now replaced by specific antivirals

Question 12

What is immunomodulation?
Side effects include inflammation e.g. blisters, burning sensation

Clinical example?

Answer 12

• Increase macrophages and pro-inflammatory cytokines

Imiquimod cream
- for genital warts, acyclovir-resistant HSV ulcer

Question 13

What is HAART? (2)

Benefits?

Answer 13

Highly active antiretroviral therapy, ‘cocktail therapy’

• for reverse transcriptase that is with high mutation rate and high resistance rate (RNA > DNA)
• 3-4 drug simultaneously to reduce resistance

Benefits

• increase life-expectancy
• reduce virus shedding, sexual transmission
• reduce viral load in pregnant women, reduce vertical transmission
• pre, post-exposure prophylaxis, reduced acquisition