Antiviral and Anti-parasitic Drugs

Question 1

What is a virus?

Answer 1

a nucleic acid in a protein coat

Question 2

Why are viruses difficult to target?

Answer 2

• replicate inside the host cell
• use host enzymes
• advanced stage before detection

Question 3

What are the different ways of targeting viruses?

Answer 3

• target virus outside the host cell

- inhibit genetic replication and integration

Question 4

When is important to target viral infections?

Answer 4

when the immune system is weakened e.g cancer, HIV

Question 5

How can you target viruses outside the host cell?

Answer 5

• vaccine (prophylaxis= before virus is contracted)

- neuraminidase inhibitors

Question 6

How do neuraminidase inhibitors work?

Answer 6

• virus released from cell remains attached via sialic acid residues
• neuraminidase produced by virus which breaks the bond
• so drug prevents virus infecting other cells

Question 7

What are the NICE guiltiness for prophylaxis/ treatment of influenza?

Answer 7

• vaccine most effective

- use neuraminidase inhibitors for at-risk patients

Question 8

What types of drugs inhibit genetic replication and integration?

Answer 8

• DNA polymerase inhibitors
• reverse transcriptase inhibitors
• integrase inhibition
• protease inhibitors

Question 9

How do DNA polymerase inhibitors work?

Answer 9

prevent DNA making DNA copies

Question 10

How do reverse transcriptase inhibitors work?

Answer 10

prevent RNA making DNA copies

Question 11

What is a pro-drug?

Answer 11

not active in the form given, have to be converted into the active form

Question 12

How does acyclovir (a DNA polyermase inhibitor) work?

Answer 12

look at slides

Question 13

What type of virus do reverse transcriptase inhibitors target?

Answer 13

RNA retrovirus (e.g HIV)

Question 14

What are the types of reverse transcriptase inhibitors?

Answer 14

• nucleoside analogues

- non-nucleosides

Question 15

How does lamivudine work (nucleoside analogue)

Answer 15

• analogue of cytosine
• phosphorylated to triphosphate
• inhibits RT (competition)-not DNA polyermase
• terminates viral DNA chain

Question 16

How do non-nucleosides work?

Answer 16

• active in the given form

- denatures active site of enzyme

Question 17

How does integrate inhibition work?

Answer 17

• Viral DNA incorporated into chromosomal DNA using the viral integrate enzyme
• the drug inhibits integrase

Question 18

What are integrase inhibitors used to treat?

Answer 18

HIV

Question 19

How does lopinavir, a protease inhibitor work?

Answer 19

• inhibits HIV protease

- reduces formation of structural proteins + enzymes

Question 20

What is lopinavir used with and why?

Answer 20

-combined with a low dose of Ritonavir (inhibits liver enzyme that metabolises protease inhibitors)

Question 21

What are the side effects of lopinavir?

Answer 21

• rash

- care needs to be taken for people with liver disease

Question 22

How is HIV usually treated?

Answer 22

-treat with 2 nucleoside RT inhibitors
-plus one of:
non-nucleoside RT inhibitors, boozed protease inhibitor, integrase inhibitor

Question 23

What are the drawbacks of treating HIV in this way?

Answer 23

• need to be treated for life (as virus is not often cleared completely from the body)
• resistance

Question 24

What is the major parasitic disease?

Answer 24

malaria

Question 25

Why does the parasite target red blood cells?

Answer 25

Hb provides a source of amino acids

Question 26

What is haemolytic and what is the symptom that occurs during this?

Answer 26

• rupturing of RBCs

- fever

Question 27

What else does the parasite do when in the RBC?

Answer 27

parasite proteins are expressed in red blood cells, these bind to the endothelium and clog blood vessels

Question 28

At what phase of the life cycle do inhibitors of haem polymerase work?

Answer 28

acute phase

Question 29

How do drugs inhibiting haem polymerase work?

Answer 29

• enzyme present in the lysosome of parasite (site of Hb metabolism-amino acids used as energy source
• converts Haem (toxic) to haemozoin

Question 30

Look at specific drugs inhibiting haem polymerase

Answer 30

on slides