Amoebicides Flashcards
What is amoebiasis?
Amoebiasis refers to gastrointestinal infection caused by the protozoan, Entamoeba histolytica, that may or may not be symptomatic and can remain latent in an infected person for several years.
What is the mode of transmission of amoebiasis?
Amoebiasis is transmitted through ingestion of foods or drinks contaminated with faeces of infected person containing the cysts of Entamoeba histolytica.
What are the classifications of amoebiasis?
Mild amoebiasis
Severe amoebiasis
What are the symptoms of mild amoebiasis?
There are no symptoms, but E. histolytica is present in the gut.
No intestinal or blood invasion and no complications.
What are the symptoms of severe amoebiasis?
- Intestinal invasion: amoebic dysentery
- Blood invasion: amoebic liver abscess, colonic perforation, severe colitis
- Complications: Colonic perforation, anaemia and severe colitis
How can you prevent amoebiasis?
- Wash hands thoroughly after using the toilet
- Clean bathrooms and toilets often especially toilet seats
- Avoid sharing towels or face washers
- Avoid raw vegetables when in endemic areas
- Boil water or treat with iodine tablets before drinking
- Avoid eating street foods especially in public places where others are sharing sauces in one container
Classes of amoebicides
- Tissue amoebicides
- Luminal amoebicides
Examples of tissue amoebicides
- Nitroimidazoles e.g., Metronidazole, Azanidazole, Secnidazole, Tinidazole
(M-A-S-T) - Isoquinolone e.g., Emetine, Dehydroemetine
Examples of luminal amoebicides
- Hydroxyquinoline e.g., Diiodohydroxyquinoline (Iodoquinol), Broxyquinoline, Tilbroquinol, Clioquinol
- Dichloroacetamide e.g., Teclozan, Etofamide, Clefamide, Diloxanide
- Aminoglycosides e.g., Paromomycin
Uses of Metronidazole
- Bacterial vaginosis
- Amoebiasis
- Giardiasis
- Trichomoniasis
- Infections caused by susceptible anaerobic organisms
- Helicobacter pylori eradication
- To prevent infection in people recovering from surgery.
What is the adult dosage of metronidazole?
400mg tabs tds for 10 days
What is the mechanism of action of metronidazole?
Unknown for Entamoeba histolytica infection.
For aneaerobic bacteria, it inhibits nucleic acid synthesis by disrupting the DNA of microbial cells following its reduction in the cells. Little effect in human and aerobic bacteria cells
Metronidazole side effects
Nausea, diarrhoea, weight loss, abdominal pain, vomiting, headache, Antabuse reaction, dizziness, and a metallic taste in the mouth.
What is an Antabuse (Disulfaram-like) reaction?
It is the generation of symptoms when alcohol is taken with a medication. e.g., nausea, vomiting, headache, increased BP, flushing & shortness of breath
Disulfaram (Antabuse) uses this mechanism to treat alcoholism.
Uses of secnidazole
Treatment of amoebiasis, giardiasis, trichomoniasis, and bacterial vaginosis
Mechanism of action of secnidazole
For aneaerobic bacteria, it inhibits nucleic acid synthesis by disrupting the DNA of microbial cells following its reduction in the cells. Little effect in human and aerobic bacteria cells
Side effects of secnidazole
GIT discomfort
Adult dose of secnidazole
1g (4 tabs) at once
Uses of Paromomycin
Treatment of amoebiasis, cryptosporidiosis, leishmaniasis and bacteria infections
Mechanism of action of Paromomycin
Paromomycin inhibits protein synthesis in non-resistant cells by binding to 16S ribosomal RNA
Side effects of Paromomycin
Nausea, diarrhea, abdominal cramps
Adult dose of paromomycin
Caps 25-35mg/kg/day in 3 divided doses for 5-10 days
Uses of Diloxanide furoate (Furamide)
Luminal amoebiasis
Side effects of Diloxanide
Skin rash, flatulence, abdominal cramps
Adult dose of Diloxanide
Tabs 500mg three times daily for 10 days
Uses of Diiodohydroxyquinoline (Iodoquinol)
Luminal amoebiasis
Mechanism of action of Iodoquinol
It acts by chelating ferrous ions essential for metabolism
Side effects of Iodoquinol
Fever, chills, hypersensitivity, thyroid gland enlargement, diarhoea
Adult dose of Iodoquinol
650mg tds for 20days
Treatment regiment for Amoebic liver abscess
Nitroimidazoles (Metronidazole 400 mg three times a day for 10 days or Tinidazole 2g once a day for 6 days)
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A luminal amoebicide Diloxanide furoate 500 mg three times a day for 10 days (or one of the other luminal amoebicides) must always be given afterwards
i.e., start treatment with tissue amoebicides; when course is completed, treat with luminal amoebicides
