EXAM #4: ANTI-PARASITIC DRUGS Flashcards Preview

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Flashcards in EXAM #4: ANTI-PARASITIC DRUGS Deck (65):
1

What are the obstacles to treating parasitic organisms?

1) Eukaryotic
2) Nearly identical cellular machinery

Thus, there are limited drug targets and a high degree of toxicity.

2

What are the the three major targets for antiparasitic chemotherapy?

1) Enzymes only in the parasite
2) Enzymes or processes found in BOTH the host/ parasite but INDESPENSIBLE to the parasite
3) Enzymes that are the same in both host and parasite but with limited toxicity to host

3

What is an example of an enzyme found only in parasites that is targeted by antiparasitic drugs?

PFOR

4

List the intestinal/ luminal parasites.

- Giardiasis
- Amebiasis
- Trichmonoiasis

5

What causes Amebiasis?

Entamoeba histolytica

6

What are the two forms of Entamoeba histolytica and Giardia?

- Trophozite form that infects gut and disseminates to other tissue
- Dormant cyst

7

What drug is used to treat the intestinal parasites?

Metronidazole

8

What is PFOR?

Pyruvate: ferrodoxin oxidoreductase

*Found only in parasites

9

What is the MOA of Metronidazole?

- Pro-drug that enters cell and is reduced by PFOR to its active form
- Reduced Metronidazole produces reactive intermediates that disrupt DNA/proteins

10

What adverse effects are associated with Metronidazole?

1) Metallic taste
2) Disulfram-like effect

*Thus, patients should avoid alcohol*

11

If you're treating a patient for Trichomoniasis with Metronidazole, what do you need to remember?

Trichomoniasis is a STD--need to treat the partner too

12

What form of Amebiasis is Metronidazole good at treating?

Trophozoites that have left the gut

*Does NOT do a good job treating the cyst form*

13

What drugs are used to follow-up Metronidazole treatment in Amebiasis?

1) Iodoquinol OR
2) Paromomycin

*Now Paromomycin is more commonly used--less toxicity and shorter treatment course*

14

What is Halogenated hydroxyquinoline good at treating?

BOTH forms of Entameba histolytica in the LUMEN

15

What is Paromomycin good at treating?

BOTH forms of Entameba histolytica in the LUMEN

16

What are the major opportunistic parasitic infections of AIDS patients and the immunocompromised?

1) Cryptosporidium parvum
2) Pneumocystis jiroveci
3) Toxoplasma gondii

17

What disease is caused by Cryptosporidium parvum?

Cryptosporidiosis--profuse watery diarrhea
- Self-limiting in adults
- Can be fatal in immunosuppressed

18

How is Cryptosporidiosis treated?

Nitazoxanide

19

What is the MOA of Nitazoxanide?

Inhibition of PFOR that disrupts energy metabolism in the parasite

20

In addition to Cryptosporidiosis, what else can Nitazoxanide treat?

Giardiasis

21

How are Pneumocystis jirovecii and Toxoplasma gondii treated?

Inhibitors of folate synthesis
- TMP-SMX
- Pyrimethamine-Sulfadiazine

22

What is the MOA of Sulfonamides?

PABA analog that inhibit DIHYDROPTEROATE SYNTHASE

23

What is the MOA of Diaminopyrmidines?

Inhibitors of DHFR that prevent formation of tetrahydrofolate

24

What is the major adverse effect seen with Sulfonamides?

Rash

25

What is an adverse effects seen with Pyrimethamine-Sulfadiazine treatment?

- Folic acid deficiency
- Can cause megaloblastic anemia

*Note that this is used for Toxoplasmosis*

26

How can folate deficiency in Pyrimethamine-Sulfadiazine treatment be treated?

Leucovorin rescue

27

What is the MOA of resistance to the folate synthesis inhibitors?

Point mutations in the enzyme targets

28

What drug is used to treat the hepatic stage of Malaria infection?

Primaquine

29

What is the major target of most of the Malaria drugs?

RBC cycle of replication

30

What the MOA of Chloroquine?

Unclear- maybe interferes parasite ability to detoxify metabolites

31

Where is Chloroquine used today?

West of the panama canal?

32

What is the mechanism of Chloroquine resistance?

Drug export pumps

33

What is the MOA of quinine?

- May interfere with Hb degradation and cause accumulation of toxic metabolites
- May complex with parasite DNA to prevent replication

34

What do you need to remember about Quinine?

Poor TI--associated with:
1) Cinchonism
2) Hypoglycemia

35

How is Quinine used to treat Malaria?

- NOT for prophylaxis b/c of toxicity
- Used IV if positive diagnosis

36

How is Mefloquine used to treat Malaria?

Prophylaxis

37

What adverse effects are associated with Mefloquine?

Severe neuropsychiatric reactions

38

What is the MOA of Primaquine?

- Prodrug
- Interferes with electron transports
- May inhibit pyrimidine synthesis

39

What do you need to remember about Primaquine?

ONLY DRUG available for liver/hypnozoite form

40

What species of malaria are associated with a liver form?

P. vivax
P. ovale

41

What toxicity is seen with Primaquine?

If taken by a patient with G6PD, can lead to hemolysis

*Thus, screen for G6PD before administering

42

What is Malarone good for treating?

P. falciparum

*Good for treatment and for prophylaxis*

43

What is Malarone?

Combination of Atoaquone and Proguanil

44

What is the MOA of Proguanil?

Inhibits DHFR

45

What is the MOA of Doxycycline?

Inhibits plasmodium protein synthesis

46

How is Doxycycline used to treat Malaria?

Prophylaxis

47

What are the major side effects of Doxycycline?

- Photosensitivity dermatitis
- Staining of teeth in kids

48

What patient populations is Doxycycline contraindicated in?

1) Children
2) Pregnant women

49

What is Artemisinin derived from?

Chinese wormwood

50

What is the clinical utility of Artemisinin?

Effective treatment for multi-drug resistant strains of P. falciparum

51

What is the general MOA of the antihelminthic drugs?

1) Inhibit mitosis of the parasite
2) Cause muscle paralysis of the parasite (allows the organism to be passed more easily)

52

List the Benzimidazoles.

Albendazole
Mebendazole
Thiabendazole

53

Which of the Benzimidazoles has the greatest toxicity? Why?

Thiabendazole--more easily absorbed into system circulation than the others

54

How are the Benzimidazoles normally given?

Orally on an empty stomach

55

What toxicities are associated with Thiabendazole?

CNS disturbances--delerium and hallucinations

56

In what patient populations are the Benzimidazoles contraindicated?

Pregnant women

57

What infections are Albendazole and Mebendazole used to treat?

Ascariasis
Pinworm
Hookworm
Whipworm

*Note that this is done with a SINGLE dose

58

What is Thiabendazole used to treat?

1) Topical preparation for cutaneous larval migrans
2) Strongyloidiasis (2nd line)

59

What is the MOA of Ivermectin?

Causes muscle paralysis in parasites BUT not in humans

60

What is Ivermectin the drug of choice for?

1) Strongyloidiasis
2) Tissue dwelling nematodes including:
- O. volvulus (river blindness)
- Loa loa (eye worm)
- W. bancrofti (elephantiasis)

(Thiabendazole is second line for Strongyloidiasis)

61

What is the MOA of Pyrantal Pamoate?

Depolarizing neuromuscular blockade

62

What is Pyrantal Pamoate the drug of choice for?

Pinworm

*Note that only 2 doses are needed*

63

What do you need to remember about Pinworm infections?

Treat the ENTIRE household

64

What drug is used to treat Tapeworm and Fluke infections?

Praziquantel

65

What is the MOA of Praziquantel?

- Increased the Ca++ permeability of the cuticle covering these worms
- Causes depolarizing neuromuscular blockade/ paralysis

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