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MD3002 Pharmacology > Anti-helminthics and Anti-Protozoals > Flashcards

Anti-helminthics and Anti-Protozoals Flashcards

1
Q

Name some SI protozoal infection of the GI tract?

A
  • Giardia lamblia

- Cryptosporidium parvum

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2
Q

Name a LI protozoal infection of the GI tract?

A
  • Entamoeba histolytica
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3
Q

What are the 2 stages of the Gardia lamblia life cycle?

A
  • Trophozoite

- Cyst

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4
Q

What are the features of the trophozoite stage of the G. lamblia stage?

A
  • Flagellated and bi-nucleated
  • Lives in the upper part of the SI
  • Adheres to brush border of epithelial cells
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5
Q

What are the features of the cyst stage of the G. lamblia stage?

A
  • Formed when trophozoite forms resistant wall
  • Passes out in stools
  • Can survive for several weeks
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6
Q

How are intestinal trophozoite infections treated?

A

Single dose metronidazole or tinidazole

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7
Q

Explain the life cycle of C. parvum

A
  • Asexual and sexual development within host
  • Ingestion of resistant oocysts
  • Release of infective sporozoites in SI
  • Invasion of intestinal epithelium
  • Division to form merozoites which re-infect cells
  • After sexual phase, oocytes released
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8
Q

What can the presentation of C. parvum infection be like?

A

Painful, watery diarhoea for a week or more

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9
Q

What drugs have been suggested to work against Cryptosporidial infection?

A
  • Paromomycin
  • Nitazoxanide
  • Spiramycin
    Limited evidence that it works for very immunocompromised patients
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10
Q

Describe the life-cycle of Entomaeba histoltica

A
  • Transmitted through contaminated food/water or anal sexual activity
  • Cysts pass through stomach and and excyst in the SI giving rise to progeny
  • Adhere to epithelial cells and cause damage mainly through cytolysis
  • After mucosal invasion, cysts invade RBCs giving rise to amoebic colitis
  • Trophozoite stages live in colon and pass out as resistant, infective cysts
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11
Q

Where is entomaeba histolytica prevelant?

A

Tropical and sub-tropical countries (> 50% of population)

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12
Q

What is intestinal amoebiasis treated with?

A
  • Metronidazole (chronic infection cysts survive and are resistant)
  • Amoebic abscess (e.g liver abcess) requires treatment with metronidazole at higher and longer doses
  • Chronic infection needs treatment with diloxanide furoate
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13
Q

What is metronidazole used to treat and how does it work?

A
  • Antiprotazoal agent
  • Active against Entamoeba histolytica and Giardia lamblia
  • Penetrates well into tissue - hence its value in amoebic liver abscess
  • Under anaerobic conditions it generates toxic radicals that damge bacterial and protozoal DNA
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14
Q

What are some of the side-effects of metronidazole?

A
  • Metallic taste is common and can be hard to tolerate

- Cause an acute nauseous reaction with alcohol

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15
Q

What is Diloxanide furoate?

A
  • A luminal amoebicide
  • Does not get out of gut
  • Irradicatess amoebes
  • irrradicates cystic form
  • Usually well tolerated
  • Flatulence, itchiness and hives are associated with use
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16
Q

What other drug has a very similar affect to diloxanide?

A

Paromomycin (adverse events do include diarrhoea, heartburn, nausea and vomiting)

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17
Q

What is Oral Rehydration Therapy?

A
  • Involves the replacement of fluids and electrlytes lost during diarrheal illness
  • Solution increases the resorption of fluids and salts into intestinal wall
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18
Q

What percentage of cases of acute, watery diarrhoea can be successfully treated with an oral rehydration solution (ORS)?

A

90 - 95%

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19
Q

How can protozoal infections of the GI tract be prevented?

A
  • Improving hygiene and water supplies
  • Eating only freshly prepared food served hot
  • Avoiding salads and fruit which cannot be peeled
  • Avoiding tap water and ice cubes
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20
Q

What are the 3 main classes of helminths?

A
  • Nematodes (roundworms)
  • Cestodes (tapeworms)
  • Trematodes (flukes)
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21
Q

What are the 2 main classes of nematodes?

A
  • Blood and tissue

- Intestinal

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22
Q

Give some examples of blood and tissue nematodes?

A
  • Brugia
  • Wucheraria
  • Onchocerca
  • Mansonella
  • Loa loa
  • Toxocara
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23
Q

Give some examples of intestinal nematodes?

A
  • Ascaris
  • Hookworm
  • Enterobius
  • Trichiuris
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24
Q

What are the 2 main types of Cestodes?

A
  • Taenia

- Echinococcus

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25
Q

Give 2 examples of Taenia Cestodes

A
  • Taenia solium

- Taenia saginata

26
Q

Give 2 examples of Echinococcus Cestodes

A
  • Echinococcus granulosus

- Echinococcus multilocularis

27
Q

What are the 3 main places trematodes can be found?

A
  • Lungs
  • Liver
  • Blood
28
Q

What trematode can be found in the lung?

A

Paragonomiasis

29
Q

What trematodes can be found in the liver?

A
  • Opisthorcis (fish)

- Fasciola (sheep)

30
Q

What trematodes (flukes) can be found in the blood?

A
  • Schistosoma mansoni
  • Schistosoma haematobium
  • Schistosoma japonicum
31
Q

Give some examples of helminthic vectors and what helminths are carried in them?

A
  • Flies: Onchocerciasis
  • Aedes mosquito: Filariasis
  • Crysops: Guinea worm
  • Snails: Schistosomiasis, Capillaria, Fasciola
32
Q

Describe the Schistosomiasis life cycle

A
  • Human intestine or bladder
  • Eggs in urine or faeces are released in water
  • Eggs hatch in water
  • Become miracidium
  • Enter snails (complex life-cycle in the snail)
  • Cercariae exit the snail (thermotropic, negatively geotropic and phototropic)
  • Enter skin and migrate through body into bladder or intestine
33
Q

What are the pathological mechanisms of helminthic infections?

A
  • Inflammation
  • Competition for nutrients
  • Space occupying lesions
  • Stimulation of fibrosis
34
Q

Give some examples of paraistes where inflammation is the main pathogenic mechanism?

A
  • Filariasis
  • Onchocerciasis
  • Toxocariasis
  • Cysticercosis
  • Schistosomiasis (can get bladder cancer and bladder fibrosis)
  • Enterobius
35
Q

What part of filaria and onchocerca cause inflammation?

A
  • Wolbachia bacteria which live inside them

- They control the gender of filaria, kill of males

36
Q

What happens when e. coli / wolbachia / gram -ve bacteria are killed in the blood?

A

LPS causes shock - killing filaria can cause this

37
Q

What can the inflammation caused by filiaria cause in the lymphatics?

A

Elephantiasis

38
Q

What can competition for nutrients by helminths cause?

A
  • major threat to health
  • Intellectual development slowed due to less micronutrients
  • More severe with poor nutrition
39
Q

What are the clinical features of Trichiuris?

A
  • Vague abdominal symptoms
  • Trichiuris dysentery syndrome
  • Growth retardation
  • Intellectual comprimise
    Micronutrient deficiency
    Mucosal integrity
40
Q

What are examples of space occupying lesions?

A
  • Eggs in the wrong place
  • Cysticercosis causing CSF obstruction
  • Ascaris causing intestinal obstruction
  • Hydatid cyst in the liver
41
Q

What is Trichuris trichiura?

A
  • Whipworm
  • Can live for 3 yrs in gut
  • Acquired through ingesting eggs on vegetables
  • 10,000 eggs produced daily
  • 800 million cases worldwide
42
Q

Where are enterobius vermicularis found?

A
  • Anus (causes intense itching and possible secondary bacterial infection)
  • Female lays 10,000 eggs here at night which may develop into infective stage in hrs
43
Q

What type of helminths are Enterobius vermicularis?

A
  • Threadworm

- Small cylindrical nematodes < 1 cm

44
Q

What type of worm is strongyloides stercoralis?

A

Pinworm

45
Q

How does strongyloides stercoralis affect the intestines?

A
  • Disruption of SI mucosa
  • Villous atrophy
  • Marked loss of intestinal wall
46
Q

What are the clinical manifestations of strongyloides stercoralis?

A
  • Dysentery (persistant in immunocompromised hosts)
  • Dehydration
  • Malabsorption syndrome
  • Anal pruritis
  • Association with appendicitis
47
Q

How are helminth infections treated?

A
  • Inflammation is treated with anti-inflammatory e.g steroids
  • Competition for nutrients is treated by reducing worm burden and by supporting nutrition + surgery, decompression
  • Helminth eradication is important + treating secondary effects (essential when fibrosis occurs as a result of infection)
48
Q

What drug is used to treat cestode infection?

A
  • Praziquantel

- Anti-epileptic drugs plus anti-helminthic treatment with steroids

49
Q

What does praziquantel do?

A
  • Likely increases calcium permeability of membranes depolarising them
  • May interfere with purine synthesis
  • Treat cestode, schistosomiasis
  • Clonorchis, fascioliasis and paragnomiasis infection
50
Q

Where is praziquental excreted?

A

Kidneys

51
Q

What is albendazole used to treat?

A
  • Nematode infection

- Some protozoa such as giardia

52
Q

What is the mode of action of albendazole?

A
  • Binds to colchicine sensitive receptor or tubulin
  • Prevents polymerisation into MTs
  • Impaired glucose uptake and depleted glycogen stores
  • Degenerative changes int the worm
53
Q

What can the side-effects of albendazole be?

A
  • Relitavely safe drug
  • Relatively common
  • Conc in semen therefore may be teratogenic
  • Persistant sore throat
  • Headaches, dizziness and seizures
  • Acute liver failure
  • Aplastic anaemia and marrow supression
54
Q

What is piperazine used to treat?

A

Ascariasis and enterobius infection

55
Q

What can pyrantel be used to treat?

A

Hookworms and roundworms

  • Causes depolarising neuromuscular blockade
  • Can cause intestinal obstruction
56
Q

What can ascaris be mixed with to treat hookworm infection?

A

Levamisole

57
Q

What can dithyl carbanasine be used for?

A
  • Diagnostically, kills microfiliaria of oncoserca

- Causes worms to go to skin and can be seen in biopsy

58
Q

What can ivermectin be used against?

A
  • Filarial worms, lice, scabies, bed bugs

- Complicated CNS depression

59
Q

What is the drug of choice to treat nematodes?

A

Albendazole

60
Q

What control measures can be taken to prevent intestinal helminths?

A
  • Vector control for filariasis
  • Meat inspection for cysticercosis (white spots on meat)
  • Sanitation and hygiene for intestinal nematodes

MD3002 Pharmacology (7 decks)

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