Antivirals, Antifungals and Antiprotozoals

Question 1

What are the 2 major classes of antiviral drugs used to treat flu?

Answer 1

M2 ion channel blockers

Neuraminidase inhibitors

Question 2

Give 2 examples of M2 ion channel blockers

Answer 2

Amantadine

Rimantidine

Question 3

Give 2 examples of neuraminidase inhibitors

Answer 3

Oseltamivir (Tamiflu)

Zanamivir

Question 4

What is Amantadine used to treat?

Answer 4

Parkinson’s

Influenza A

Question 5

What is the mechanism of action of M2 ion channel blockers

Answer 5

Block M2 ion channels on viral envelope

Therefore prevent entry of H2 into virus, which prevents viral uncoating and hence also prevents viral DNA release

Question 6

Give 4 ADRs of M2 ion channel blockers

Answer 6

Dizziness
GI
Hypotension
Confusion

Question 7

What can the neuraminidase inhibitors be used for?

Answer 7

Influenzas A + B including avian strains and H1N1.

Also useful in M2 ion channel blocker resistant Influenza A

Question 8

What is the mechanism of action of neuraminidase inhibitors?

Answer 8

Inhibit the viral enzyme neuraminidase that allows release of new viral particles into the circulation
Therefore particles remain bound to exterior side of host cell membrane

Question 9

How is Tamiflu administered?

What about Zanamivir?

Answer 9

Tamiflu - oral

Zanamivir - dry aerosol - straight to lungs

Question 10

Give 4 ADRs of neuraminidase inhibitors (3 common and 1 rare)

Answer 10

Common:
- GI
- Headache
- Epistaxis
Rare - bronchospasm

Question 11

What are the 2 major classes of antifungal drug?

Give 2 examples of each

Answer 11

Azoles - clotrimazole, fluconazole

Polyenes - nystatin, amphotericin

Question 12

How are the antifungal drugs normally administered?

Answer 12

Clotrimazole and nystatin - topical

Fluconazole - oral

Question 13

What is the mechanism of action of the azoles?

Answer 13

Inhibit ergosterol synthesis which is part of fungal cell wall - hence disrupt cell wall

Question 14

What is the mechanism of action of the polyenes?

Answer 14

Bind to ergosterol in fungal cell wall - creates pore through which ions leak out - causes lysis

Question 15

Give 4 ADRs of fluconazole

Answer 15

GI
Headache
Hepatitis
Prolonged QT interval

Question 16

Give 2 examples of antiprotozoal drugs

Answer 16

Chloroquine

Metronidazole

Question 17

Give some uses of Metronidazole

Answer 17

• 1st line against C. diff
• Oral infections/surgical infections caused by anaerobes
• Protozoal infections such as trichomonas vaginitis

Question 18

What is the mechanism of action of Metronidazole?

How does this explain their spectrum of use?

Answer 18

Enters cell, then reduced to produce free radical which causes DNA damage and cell death
No good in aerobes as they cannot reduce the drug molecule

Question 19

Give 3 ADRs of Metronidazole

Answer 19

GI
Hypersensitivity
Neuro

Question 20

What is really important about Metronidazole use?

Answer 20

Mustn’t drink alcohol for duration of course + 48 hours

Question 21

What is the mechanism of action of chloroquine?

Answer 21

Prevents polymerisation of toxic haem to less toxic haemozoin (produced when parasite digests Hb) - leads to lysis of parasite.

Question 22

Give 3 ADRs of chloroquine

Answer 22

GI upset
Pruritis
Blurred vision