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MD3002 > Anti-helminthics and Anti-protozoals > Flashcards

Anti-helminthics and Anti-protozoals Flashcards

1
Q

Describe the treatment of G. lamblia.

A

Intestinal trophozoite is treated with metronidazole or tinidazole (single dose)

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2
Q

Describe the treatment of C. Parvum.

A
  • Drugs have been proposed for use: paromomycin, nitazoxanide and spiramycin
  • BUT limited evidence that any of these drugs have an impact on the severity or duration of diarrhoea in the most immunocompromised patients
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3
Q

How can we distinguish between small and large intestine disease based on stools ?

A

infrequent large stools = small intestine (e.g. salmonella infection)

frequent small stools = large intestine (e.g. amoebic colitis)

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4
Q

Describe the treatment of amoebiasis.

A
  • Intestinal infection is treated with metronidazole
  • In chronic infection cysts will survive and cause relapse and are resistant to metronidazole
  • Chronic infection needs treatment with diloxanide furoate
  • Amoebic abscess requires treatment with metronidazole at higher and longer doses
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5
Q

What type of medication is metronidazole ? What is its mechanism of action ?

A

Originally an antiprotozoal agent.

Under anaerobic conditions it generates toic radicals that damage bacterial and protozoal DNA. Penetrates well into tissue – hence its value in amoebic liver abscess.

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6
Q

What pathogens is metronidazole effective against ?

A

Active against Entamoeba histolytica and Giardia lamblia

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7
Q

What are issues with the use of metronidazole ?

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

* Cause an acute nauseous reaction with alcohol

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8
Q

Diloxanide furoate

  • Indication
  • Type of drug
  • Side effects
A

Diloxanide furoate

  • Indication: Chronic amoebiasis infection
  • Type of drug: luminal amoebicide
  • Side effects: flatulence, itchiness, and hives are associated with use (but isually well tolerated with minimal toxicity)
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9
Q

Identify drugs on the WHO essential medicines list.

A 
Diloxanide furoate
Praziquantel
Albendazole
Levamisole
Diethyl carbamazine
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10
Q

Paromomycin

  • Type of drug
  • Indication
  • Mechanism of action
  • Administration
  • Side effects
A

Paromomycin

  • Type of drug: aminoglycoside
  • Indication: C parvum infection
  • Mechanism of action: Kills amoebic cystic stage
  • Administration: Orally (but not absorbed from GI tract)
  • Side effects: abdominal cramps, diorrhoea, heartburn, nausea, and vomiting
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11
Q

What treatment is needed for any diarrheal illness ?

A

ORT
• Involves the replacement of fluids and electrolytes lost during diarrheal illness
• 90-95% of cases of acute, watery diarrhoea can be successfully treated with an oral rehydration solution (ORS)
• ORS increases the resorption of fluids and salts into the intestinal wall

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12
Q

Identify measures to prevent protozoal infections of the GI tract.

A
  • Improved 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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13
Q

Identify the main helminthic pathogens.

A

NEMATODES (ROUNDWORMS)

1) Blood and Tissue Nematodes
- Brugia
- Wucheraria
2) Intestinal Nematodes
- Ascaris
- Hookworm
- Trichiuris

CESTODES (FLATWORMS/TAPEWORMS)

1) Taenia (cause disease in humans)
- Taenia solium
2) Echinococcus (cause disease in animals)
- E. granulosus

TREMATODES (FLUKES)

1) Lung
- Paragonomiasis
2) Liver
- Opisthorcis
3) Blood
- S. mansoni

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14
Q

What is so special about the replication of helminths in the human body ?

A

If ingest one egg, get one worm, direct relation (doesn’t ever change, doesn’t really replicate in the body, except for a couple exception). If can drop amount of infection people get, may lure the worm burden into something that doesn’t cause any disease

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15
Q

Identify some hosts for helminths.

A
  • Wild bore (tinea solium)
  • Rats
  • Humans
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16
Q

Identify some vectors for helminths, along with the species each carries.

A
  • Flies: Onchocerciasis
  • Aedes mosquito: Filariasis
  • Crysops: Guinea worm
  • Snails: Schistosomiasis, Capillaria, Fasciola
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17
Q

How do Schistosomiasis infections occur ?

A

Eggs in water, survive until find snail, then
develops. What emerges through these stages is the Cercariae which are
programmed to find something hot(i.e. a person), then burrow through skin, cause a bit of a lesion, then go into liver and mate and produce eggs (cause hepatosplenomegaly)

18
Q

Identify the main pathological mechanisms of helminths.

A
  • Inflammation
  • Competition for nutrients
  • Space occupying lesions
  • Stimulation of fibrosis
19
Q

Identify species of helminths for which inflammation is the main pathogenic mechanism.

A
  • Filariasis

* Onchocerciasis

20
Q

Describe the main features of inflammation in filarial infection.

A

1) Filaria do cause the disease but actually not them themselves, it’s Wolbachia bacteria living inside them that cause the disease (same as for Onchocerca helminth).
From a therapeutic POV, once kill worm, release bacteria, so worsened infection and inflammation

2) Filarial infection also associated with
acute lymphoedema, which leads to repeated cycles of inflammation and
bacterial infection, leading to Elephantiasis

21
Q

Identify species of helminths for which competition for nutrients is the main pathogenic mechanism.

A
  • Hookworms (blood)
  • Ascaris
  • Tapeworms
  • Trichiuris trichiura
22
Q

What are possible clinical consequences of infection by helminths which compete for nutrients ?

A
  • Intellectual development may be slowed

* In general, major threat to health

23
Q

True or false: consequences of infection by helminths which compete for nutrients are more severe with poor nutrition

A

True

24
Q

What are the main clinical features of Trichiuris clinical features ?

A 
• Vague abdominal symptoms
• Trichiuris dysentery syndrome (bloody mucoid diarrhea, small frequent stools...)
• Growth retardation
• Intellectual compromise
-micronutrient deficiency
-mucosal integrity
25
Q

What is management for Hookworm infections ?

A
  • Anaemia medication

- Diet changes (to compensate for loss of blood)

26
Q

Identify the main space occupying lesions of helminths.

A
  • Eggs in the wrong place (e.g. Echinococcus causing Hydatid cyst in the liver)
  • Cysticercosis causing CSF obstruction (can lead to seizures)
  • Ascaris causing intestinal obstruction
27
Q

What is the management required for CSF obstruction caused by Cysticercosis ?

A

Antibitoics unimportant, probably requires operation

28
Q

Identify the main approach to the treatment of helminth infections.

A

Differs depending upon the pathogenesis

1) Inflammation → Anti-inflammatory eg., steroids
2) Competition for nutrients → Reduce worm burden and support nutrition
3) Space occupying lesions → Surgery, decompression (latter could be done with steroids)
4) Stimulation of fibrosis → Surgery

+ for all, helminth eradication and treatment of secondary effects

29
Q

Describe treatment of intestinal Cestodes.

A
  • Praziquantel (rarely, Niclosamide)

- if cysticercosis, then necessary to continue anti-epileptic drugs and combine anti-helminthic treatment with steroids

30
Q

Describe treatment of intestinal Nematodes.

A
  • albendazole mainly
  • piperazine, Pyrantel, Levamisole, Diethyl carbamazine, Ivermectin rarely
  • remember that a single dose or course of treatment is rarely enough as you must engage with the family and the environment (NB Enterobius infection)
31
Q

Praziquantel

  • Indication
  • Mechanism of action
  • Features of absorption and excretion
  • Dose
  • Half life
A

Praziquantel

  • Indication: Intestinal cestodes (including for Hydatid disease, Cysticercosis, Schistosomiasis, Fascioliasis)
  • Mechanism of action: Not fully known, probably increases calcium permeability of membranes depolarising them + may interfere with purine synthesis
  • Features of absorption: Well absorbed orally, but significant first pass effect, and low systemic concentrations. Excretion in the kindeys
  • Dose: 20 mg/kg
  • Short half life
32
Q

Identify side effects of Praziquantel.

A
  • Dizziness, headache, drowsiness and somnolescence, rarely seizures
  • Abdominal cramps and nausea, Diarrhoea
  • Transient asymptomatic rise in transaminases
  • Urticaria, rash and pruritis
  • Interacts with rifampicin (decreased concentrations), carbamazine, phenytoin (reducing praziquantel bioavailability)
33
Q

ALBENDAZOLE

  • Drug class
  • Indications
  • Mechanism of action
  • Side effects/contraindications
A

ALBENDAZOLE
-Drug class: benzimidazole

-Indications:
1) Treatment of nematode infections: trichiuriasis, filariasis, Enterobius infection, ascariasis, hookworm, toxocariasis, strongyloidiasis
2) Treatment of some protozoa: giardia
3) Treatment of some cestode infections:
Neurocysticercosis and hydatid disease

-Mechanism of action:
• Binds to colchicine sensitive receptor or tubulin
• This prevents polymerisation into microtubules
• Impaired glucose uptake and depleted glycogen stores
• Degenerative changes appear in the worm

-Side effects: 
• Concentrated in semen and may be teratogenic
• Persistent sore throat
• Headaches dizziness and seizures
• Acute liver failure
• Aplastic anaemia and marrow supression
34
Q

PIPERAZINE

  • Indications
  • Mechanism of action
  • Features of absorption
  • Half life
  • Side effects/contraindications
A

PIPERAZINE
-Indications: Intestinal Nematodes (specifically ascariasis and enterobius infection)

  • Mechanism of action: Agonist activity against the gamma butyric acid receptor paralysing muscular activity
  • Features of absorption: Orally active, metabolism in liver
  • Half life: Variable half life
  • Side effects: GI tract upset and rarely hypersensitivity, dizziness
35
Q

PYRANTEL

  • Indications
  • Mechanism of action
  • Features of absorption and excretion
  • Side effects/contraindications
A

PYRANTEL
-Indications: Treatment of hookworms and roundworm

  • Mechanism of action: Causes depolarising neuromuscular blockade
  • Features of absorption: Poorly absorbed providing selective toxicity. Excreted unchanged in the faeces.
  • Side effects: Can cause intestinal obstruction if there is a heavy worm load + Antagonistic with piperazine + Avoid in pregnancy,
36
Q

LEVAMISOLE

  • Indications:
  • Mechanism of action:
  • Features of absorption and excretion
  • Side effects/contraindications
A

LEVAMISOLE

  • Indications: Ascariasis and mixed ascaris hookworm infection
  • Mechanism of action: Nicotinic acetylcholine receptor antagonist
  • Features of absorption and excretion: Rapidly absorbed
  • Side effects: Caution in pregnancy + Abdominal pain, nausea and vomiting are reported
37
Q

DIETHYL CARBAMAZINE

  • Class of drug
  • Indications
  • Mechanism of action
  • Side effects/contraindications
A

DIETHYL CARBAMAZINE
-Class of drug: piperazine derivative

  • Indications: Filaria infection
  • Mechanism of action: Inhibits arachidonic acid making parasites more susceptible to immune attack
  • Side effects: Associated with increase in inflammation: caution Mazzotti reaction, loss of site in onchocerciasis
38
Q

IVERMECTIN

  • Indications
  • Mechanism of action
  • Side effects/contraindications
A

IVERMECTIN
-Indications: Active against fliarial worms, lice, scabies and bed bugs. Currently being used for eradication of lymphatic filariasis and onchocerciasis

  • Mechanism of action: Ivermectin binds glutamate-gated chloride increase in the permeability of the cell membrane to chloride ions with hyperpolarization of the nerve or muscle cell resulting in paralsysis and death of the parasite either directly or by causing the worms to starve.
  • Side effects/contraindications: Contraindicated in children < 5 or breast feeding mothers + Complicated by CNS depression + Increased risk of absorption past the blood brain barrier of HIV protease inhibitors, calcium channel blockers and glucocorticoids
39
Q

NICLOSAMIDE

  • Indications
  • Mechanism of action
  • Side effects/contraindications
A

NICLOSAMIDE

  • Indications: tape worm infections (kills adult worms only, not eggs)
  • Mechanism of action: Inhibits glucose uptake, oxidative phosphorylation and anaerobic metabolism

-Side effects/contraindications:
Dizziness, skin rashes, drowsiness + perianal itching.

40
Q

Identify prevention and control measures of intestinal helminths.

A
  • Vector control for filariasis
  • Meat inspection for cysticercosis
  • Sanitation and hygiene for intestinal nematodes

MD3002 (95 decks)

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