Anti-fungal and anti-parasitic drugs

Question 1

List factors that predispose to fungal infections?

Answer 1

Moisture and warmth, broad-spectrum antibiotics, diabetes mellitus, immunodeficiency

Question 2

List the four major anti-fungal infections

Answer 2

Cell membrane synthesis inhibitors
Cell membrane disrupters
Cell wall synthesis inhibitors
Antimetabolites

Question 3

What three drugs groups fall under cell membrane synthesis inhibitors?

Answer 3

Azoles
Non-azole inhibitors
Others

Question 4

Give an example of a drug class that is a cell membrane disruptor.

Answer 4

Polyenes (amphotericin, nystatin)

Question 5

Give an example of a drug class that is a cell wall synthesis inhibitors.

Answer 5

Caspofungin

Question 6

Give an example of a drug class that is a antimetabolite.

Answer 6

Flucocytosine

Question 7

What is the mechanism of action of azoles?

Answer 7

Inhibit ergosterol synthesis through inhibition of 14 alpha-demethylase.
Increase 14 alpha-methyl sterols in cell, which disrupts phospholipids, inhibit growth and interfere with membrane-bound enzyme systems.

Question 8

Are azoles fungistatic or fungicidal?

Answer 8

Fungistatic

Question 9

Are azoles broad or narrow spectrum?

Answer 9

Broad

Question 10

What are ADRs of azoles?

Answer 10

Hepatic drug interactions as 14alpha-demethylase CYP450 enzyme
local skin irritation, abdominal cramping, diuresis.

Question 11

What is the mechanism of action of polyene antibiotics?

Answer 11

Disrupt cell membrane integrity by binding irreversibly to ergosterol and disrupting cell membrane (changes permeability)

Question 12

Is polyene fungicidal or fungistatic?

Answer 12

Smaller doses - fungistatic

Larger doses - fungicidal

Question 13

What is polyene used for?

Answer 13

nephrotoxicity, anorexia, malaise, fever

Question 14

What are the three targets of anti-malarial drugs?

Answer 14

Protozoal DNA, mitochondrial function, membrane structure.

Question 15

What is the mechanism of action of folic acid antagonists?

Answer 15

Antagonise the availability of folic acid for DNA replication, restricting growth.

Question 16

What are the ADRs of folic acid antagonists?

Answer 16

Methaemoglobinaemia (methylation of haemoglobin), headache, GI disturbances.

Question 17

What is the function of chloroquine, hydroxychloroquine and quinine?

Answer 17

Bind to DNA to suppress DNA replication and transcription.

Question 18

What are ADRs of “quine” antimalarials?

Answer 18

Blindness in long term therapy

Tinnitus, visual disturbances, erythrocyte haemolysis.

Question 19

What is the mechanism of action of doxycyline?

Answer 19

Alter mitochondrial function, suppressing metabolism.

Question 20

What are ADRs of doxycycline?

Answer 20

Photosensitivity, skin rashes, GI disturbances

Question 21

What is the mechanism of action of mefloquine?

Answer 21

Membrane disruptor- prevents breakdown of blood pigment, which is toxic to the parasitic membrane. Also, binds to RBC membrane to prevent entry.

Question 22

What are ADRs of mefloquine?

Answer 22

Psychiatric illness, headache, dizziness.

Question 23

What are the three helminths that infect humans?

Answer 23

Nematodes (roundworms), cestodes (tapeworks), trematodes (flukeworms)

Question 24

What is the major effect of drugs against intestinal nematodes?

Answer 24

Paralysis of the worm, directly or indirectly.

Question 25

What is the mechanism of action of pyrantel?

Answer 25

Direct paralysing agent.

Blocks cholinesterase. Poorly absorbed in the GI tract.

Question 26

What is the mechanism of action of ivermectin?

Answer 26

Indirect paralysing agent.
Enhances GABA action, may also open inhibitory glutamate-mediated Cl- channels.
Broad-spectrum.

Question 27

What is the mechanism of action of benzimidazoles?

Answer 27

Indirect paralysing agents.

Inhibit microtubule synthesis synthesis in eggs, larvae and adults.

Question 28

What are side effects of benzimidazoles?

Answer 28

Teratogenic, headache, dizziness, abdominal cramps, diarrhoea.