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Semester 2 Year 2 > Anti-protazoals and Anti Helminthics > Flashcards

Anti-protazoals and Anti Helminthics Flashcards

1
Q

What is the treatment of G. lamblia?

A

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

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2
Q

What is the treatment of Cryptosporidial infection

A
  • Drugs have been proposed for use: paromomycin, nitazoxanide and spiramycin
  • 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

What is 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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4
Q

Describe metronidazole

A

• Originally an antiprotozoal agent
• Under anaerobic conditions it generates toxic radicals that damage bacterial and protozoal DNA
• Active against Entamoeba histolytica and Giardia lamblia
• Penetrates well into tissue – hence its value in amoebic liver
abscess
• A metallic taste is common and can be hard to tolerate
• Cause an acute nauseous reaction with alcohol

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5
Q

Discuss Diloxanide furoate

A
  • A luminal amoebicide
  • flatulence, itchiness, and hives are associated with use
  • Usually well tolerated with minimal toxicity
  • On WHO essential medicines list
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6
Q

Describe paromomycin

A
  • An aminoglycoside
  • Given orally
  • Not absorbed from the GI tract
  • Kills amoebic cystic stage
  • Adverse events include abdominal cramps, diorrhoea, heartburn, nausea, and vomiting.
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7
Q

What worms would be most likely to be present in a ptx exposed to mosquitos of genus Aedes?

A

Filariasis (Additional Yellow + Zika risk)

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8
Q

A farmer from the mid Atlantic US complaining of GI issues was bitten by a large fly (genus Crysops), what worm is most likely present?

A

Guinea worm

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9
Q

A dumb fuck kid eats snails and big shocker, has a bad tummy, what parasites should you consider on differential?

A

Schistosomiasis, Capillaria, Fasciola

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10
Q

Describe the pathophysiology, clinical features and treatment for Schistosoma spp.

A

Pathophysiology
• Eggs are deposited in smallest venule that can accommodate the female worm
• Pathology is primarily related to sites of egg deposition, number of eggs deposited and host reaction to egg antigens

Clinical Features
• Affected by numerous factors (penetration, eggs)
• Papular rash may develop, associated with pruritus
• Granulomas replaced by collagen, scarring

Treatment
• Praziquantel, taken for 1 - 2 days

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11
Q

Describe the pathophysiology, clinical features and treatment for Filariasis

A

Pathophysiology
• [Infected] Aedes mosquito bite→ larvae
• Larvae→ lymphatics→ adult maturation→♀ microfilariae
• Lymphatic obstruction

Clinical Features
• Asymptomatic
• Swelling, abscess, enlarged lymph node(s)

Treatment
• Diethylcarbamazine (DEC)
• Ivermectin, albendazole and DEC
• Surgery

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12
Q

Describe the pathophysiology, clinical features and treatment for Trichuris trichiura
(Whipworm)

A

Pathophysiology
• Ingestion of eggs from soil
• Larvae→cecal epithelium→90 days;adults→eggs→faeces
• Worms remain embedded

Clinical Features
• Asymptomatic
• Dysentery/diarrhoea
• Colitis

Treatment
• Mebendazole
• Albendazole

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13
Q

Describe the pathophysiology, clinical features and treatment for Hookworm (Ancylostoma and Necator)

A

Pathophysiology
• Larvae penetrate the skin (foot) from soil
• Larvae→lungs (blood)→alveoli→ epiglottis→ swallowed
• In bowel adults develop, feed on blood, live ≥ 2 years.

Clinical Features
• Asymptomatic
• Pruritic papulovesicular rash
• ~Löffler syndrome
• GI disturbance

Treatment
• Albendazole and mebendazole

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14
Q

Describe the pathophysiology, clinical features and treatment for Enterobius vermicularis ((Pinworm/)Threadworm)

A

Pathophysiology
• Inhalation/ingestion of eggs
• Eggs hatch (S intestine)→adults→ mating→ migration
• Female migrates to anus at night to lay approx. 10,000 eggs, which may develop to infective stage within hours

Clinical Features
• Asymptomatic
• Intense itching (nocturnal)
• secondary bacterial infection – mild catarrhal inflammation and diarrhoea, slight eosinophilia

Treatment
• Mebendazole, pyrantel pamoate or albendazole

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15
Q

Describe the pathophysiology, clinical features and treatment for Pinworm
(Strongyloides stercoralis)

A

Pathophysiology
• Larvae penetrate skin
• Larvae→ Duodenum mucosa;adults→♀ eggs→ stool
• Disruption of small intestinal mucosa; villous atrophy
• Marked loss of elasticity of intestinal wall

Clinical Features
• Dysentery (persistent in immunocompromised hosts) &Dehydration
• Malabsorption syndrome
• Anal pruritis
• Association with appendicitis 
Treatment
• Ivermectin / Albendazole
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16
Q

What are space occupying lesions?

A
  • Eggs in the wrong place
  • Cysticercosis causing CSF obstruction
  • Ascaris causing intestinal obstruction
17
Q

How does one generally treat intestinal cestodes (flatworms)?

A

praziquantel
Treatment of other symptoms
Consider steroids

18
Q

How does one generally treat intestinal Nematodes (roundworms)?

A

Ivermectin is the most effective of the agents

  • albendazole was used liberally until Ivermectin was shown to be superior
  • levamisole and piperazine are rarely used
  • 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)
19
Q

Discuss Praziquantel

A
  • MoA not fully known: probably increases calcium permeability of membranes depolarising them
  • May interfere with purine synthesis
  • Hydatid disease
  • Cysticercosis
  • Schistosomiasis
  • Clonorchis, Fascioliasis and Paragnomiasis infection
  • Well absorbed orally
  • 20 mg/kg
  • On WHO essential medicine list
  • Significant first pass effect
  • Low systemic concentrations
  • Excreted in the kidneys
  • Short half life
20
Q

Discuss Albendazole

A

• MOA;
• 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

• Treatment of nematode infections: trichiuriasis, filariasis, Enterobius infection, ascariasis, hookworm, toxocariasis, strongyloidiasis
• Treatment of some protozoa: giardia
• Treatment of some cestode infections:
Neurocysticercosis and hydatid disease
• Other members: mebendazole, thiabendazole
• WHO essential medicine list

  • Concentrated in semen and may be teratogenic
  • Persistent sore throat
  • Headaches dizziness and seizures
  • Acute liver failure
  • Aplastic anaemia and marrow supression
21
Q

Discuss piperazine (sadly not the teratogenic one)

A
  • Agonist activity against the gamma butyric acid receptor paralysing muscular activity
  • Orally active
  • Metabolism in liver
  • Variable half life
  • Used to treat ascariasis and enterobius infection
  • SE include GI tract upset and rarely hypersensitivity, dizziness
22
Q

Discuss pyrantel

A
  • Treatment of hookworms and roundworms
  • Causes depolarising neuromuscular blockade
  • Poorly absorbed providing selective toxicity
  • Excreted unchanged in the faeces
  • Antagonistic with piperazine
  • Avoid in pregnancy
  • Can cause intestinal obstruction if there is a heavy worm load
23
Q

Discuss Levamisole

A
  • WHO List of essential medicine
  • Nicotinic acetylcholine receptor antagonist
  • Ascariasis and mixed ascaris hookworm infection
  • Rapidly absorbed
  • Caution in pregnancy
  • Abdominal pain, nausea and vomiting are reported
24
Q

Discuss Diethyl Carbamazine

A
  • A piperazine derivative
  • WHO essential medicine list
  • Inhibits arachidonic acid making parasites more susceptible to immune attack
  • Filaria infection
  • Associated with increase in inflammation: caution Mazzotti reaction, loss of site in onchocerciasis
25
Q

Discuss Ivermectin

A
  • 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.
  • Active against fliarial worms, lice, scabies and bed bugs
  • 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
26
Q

Discuss Niclosamide

A
  • Inhibits glucose uptake, oxidative phosphorylation and anaerobic metabolism
  • Used for the treatment of tape worm infections only
  • Causes dizziness, skin rashes, drowsiness and perianal itching.

Semester 2 Year 2 (1 decks)

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