Anti-parasitic drugs

Question 1

What are parasites?

Answer 1

• Fungi
• Animalia
• Protista

Question 2

How does Malaria work?

Answer 2

• Uses humans as intermediate host
• Infiltrate liver
• Develops there and then ruptures liver cells
• These infect blood stream and propagate.
• Mosquitos then pick this up and then it cycles in them and is later injected back into humans via saliva.

Question 3

List available malaria treatments?

Answer 3

• Quinine
• Chloroquinine
• Sulfadoxine/Pyrimethamine
• Melfoquine
• Artemisinin

Question 4

What is Quinine?

Answer 4

• Mechanism of action uncelar
• Interferes with ability of plasmodium to utilise haemoglobin
• Possibly inhibits purine nucleoside phosphrylase–Resulting in deficient RNA/DNA and protein biosynthesis

Question 5

What is Chloroquine?

Answer 5

• Acts by preventing crystallisation of heme from heamoglobin
• After digestion of haemoglobin protein, heme crystalises making it safe (heme is very toxic)
• Chloroquine interacts with heme and prevents it crystallisation–Leading to lysis of cell

Resistance mechanism:
1. Pump chloroquine out be CHloroquine resistance transporter (PfCRP)

Question 6

What is Artemisinin?

Answer 6

• Produces free radicals when reacting with free heme-free radicals damage cells
• Active at same stage of parasitic dev as chloroquine but also on other stages

Question 7

What are other strategies to combat malaria?

Answer 7

• Get rid of mosquitos
  1. Mosquito nets
  2. Repellents
  3. Destroy habitats (drain lakes)
  4. DTT
  5. Genetically eng/sterile mosquitos
  6. Infected mosquitos
• Vaccines
  1. Not worked so far

Question 8

What are Anti-fungal medications?

Answer 8

• Used for things like athletes foot or yeast infection

Question 9

What is Clotrimazole?

Answer 9

• For yeast infection
• Inhibits fungal cytochrome enzyme
• Inhibits conversion of lanostrerol to ergosterol
• Affects permeability of yeast cell wall
• Inhibits syntesis of membrane lipids

Question 10

What is Fluconazole?

Answer 10

• Inhibit fungal cytochrome enzyme
• Inhibits conversion of lanosterol to ergosterol
• Ergosterol is quivalent to cholesterol in human membrane

Question 11

What is Terbinafine?

Answer 11

• Used for athletes foot
• Inhibits ergosterol synthesis by inhibiting an enzyme (squalene epocidase)
• Stops conversion if squalene to lanesterol

Question 12

What are the current problems with anti-parasitic drugs?

Answer 12

• Resistance is on the increase
• Efflux pumps
• Modifying enzymes

Question 13

How do you treat parasitic worms?

Answer 13

• Drugs that act on acetyl-choline and glutamate ion channels
• Paralyses worm

Mechanisms of resistance:
* Efflux plumps
* Modifyning enzymes
* Target modifications

Question 14

Summarise anti-parasitic drugs?

Answer 14

• Parasitic infections serious problems
• Resistance developing, following same general principles as anti-bacterial and anti-virals.
  1. Target modification
  2. Drug modification
  3. Limiting access of drug to target: pumping away drugs
• Slow progress and no new drugs
• Probably due to economics- Old drugs work so no incentive
• Resistance will possibly crush the market and open it up