Antivirals

Question 1

MOA of aciclovir?

Answer 1

Pro-drug, metabolised several times. Similar to guanosine, so is incorporated into viral DNA where it acts as a chain terminator and therefore inhibits viral DNA polymerase, inhibiting DNA synthesis.

Question 2

Indications of aciclovir?

Answer 2

HSV, VZV

Question 3

AEs aciclovir?

Answer 3

GI (nausea, diarrhoea, cramps)

Neurotoxicity

Question 4

Dosing aciclovir?

Answer 4

Oral bioavailability is low so 5x per day if given PO.

Modifications are available with longer half-lives.

Question 5

Ganciclovir indications?

Answer 5

CMV in immunocomprimised.

CMV prophylaxis in immunocomprimised.

Question 6

Ganciclovir dosing?

Answer 6

IV 12 hourly for 14-21 days

Question 7

Ganciclovir A/Es?

Answer 7

Neutropenia (1 in 10)
Anaemia (1 in 10)
Leukopenia (1 in 100)
Pancytopenia (1 in 100)
Thrombocytopenia (1 in 100)
Diarrhoea
Dyspnoea
AKI
Hepatotoxicity
Tremor

Question 8

Oseltamivir indications?

Answer 8

Flu treatment in the following conditions:

• Patient presents with flu-like illness
• Onset of symptoms within last 48h (36h for zanamivir)
• Flu is circulating
• Patient is ‘at risk’

Flu prophylaxis in the following conditions:

• Patient has been in contact with someone in the last 48h (36h with zanamivir) who has presented with a flu-like illness
• Patient is ‘at risk’ group
• They are not effectively covered by vaccination
• Flu is circulating enough that when someone presents with flu like illness, it’s likely to be due to flu

Note that in both cases, clinical judgement can be used, for example in a patient in ITU whose onset was more than 48h ago.

Question 9

Conditions for flu vaccine?

Answer 9

Offered annually BETWEEN SEPTEMBER AND EARLY NOVEMBER to:

• Aged 2-16
• Aged 65+
• Six months to 64 years and “at risk” (including pregnancy!)

Question 10

Ganciclovir cautions?

Answer 10

Monitor FBC regularly

Avoid in pregnancy

Male to use barrier protection when having sex for 90 days

Question 11

Oseltamivir and zanamivir MOA?

Answer 11

Neuraminidase inhibitor - augments aggregation and release of virion

Question 12

Oseltamivir A/Es

Answer 12

Headache
Nausea
Cough

Question 13

Oseltamivir likely outcomes?

Answer 13

Shorten duration by around 0.66d

Decrease severity of symptoms by around 25%

Question 14

Which is targeted viral treatment difficult?

Answer 14

• Close relationship between virus and host

- Drug needs to penetrate the cell membrane

Question 15

What is the problem with latent viruses?

Answer 15

They cant be eliminated by current antivirals

Question 16

What does the host need with antiviral treamtent?

Answer 16

A competent immune system to finish the process