Protozoal infections like amoebiasis and giardiasis are common in areas with contaminated food and water. They affect the intestines and sometimes spread to other organs like the liver. Treatment requires drugs that can act inside the intestine as well as in body tissues, depending on the severity of the infection.
AMOEBIASIS
Amoebiasis is caused by Entamoeba histolytica. It may present as:
- Asymptomatic intestinal infection
- Amoebic dysentery (diarrhoea with blood and mucus)
- Amoebic liver abscess
The parasite has two forms: trophozoites (active form causing disease) and cysts (infective form). Treatment aims to eliminate both.
Types of Antiamoebic Drugs
Treatment is divided into:
- Tissue amoebicides – act in liver and tissues
- Luminal amoebicides – act inside the intestine to clear cysts
Tissue Amoebicides
1. Metronidazole
The most commonly used drug for amoebiasis. It kills trophozoites in tissues and intestinal walls.
Mechanism
Inside the parasite, metronidazole forms toxic free radicals that damage DNA and kill the organism.
Uses
- Amoebic dysentery
- Amoebic liver abscess
- Giardiasis and trichomoniasis (additional uses)
Side Effects
- Nausea, metallic taste
- Headache
- Disulfiram-like reaction with alcohol
2. Tinidazole
Similar to metronidazole but longer acting and better tolerated.
3. Chloroquine
Used when amoebiasis spreads to the liver. Concentrates well in liver tissue.
Luminal Amoebicides
1. Diloxanide furoate
Preferred drug to eliminate cysts from intestine.
2. Paromomycin
Non-absorbed aminoglycoside; safe in pregnancy.
3. Iodoquinol
Useful alternative luminal agent.
Treatment of Amoebiasis
1. Asymptomatic Cyst Passers
- Luminal agent alone (Diloxanide furoate or Paromomycin)
2. Intestinal Amoebiasis (Amoebic Dysentery)
- Metronidazole / Tinidazole (to kill tissue forms)
- Followed by luminal agent (to remove cysts)
3. Amoebic Liver Abscess
- Metronidazole (main drug)
- Chloroquine if needed
- Luminal agent after clinical improvement
GIARDIASIS
Giardiasis is caused by Giardia lamblia. It is commonly spread through contaminated water. It leads to symptoms such as:
- Watery diarrhoea
- Bloating and gas
- Abdominal cramps
- Malabsorption, especially in chronic cases
Drugs Used in Giardiasis
1. Metronidazole
Most widely used drug; effective and affordable.
Side Effects
- Nausea
- Metallic taste
2. Tinidazole
Equally effective as metronidazole but with fewer side effects and shorter regimen.
3. Nitazoxanide
Broad-spectrum antiparasitic also used in children.
4. Albendazole
An alternative option, particularly in mixed parasitic infections.
Treatment of Giardiasis
- Metronidazole or Tinidazole (first choice)
- Nitazoxanide (suitable for children)
- Albendazole (alternative)
Supportive Measures
- Maintain hydration
- Avoid contaminated food and water
- Treat household contacts when necessary
Important Points
- Metronidazole is effective for both amoebiasis and giardiasis.
- Always combine tissue amoebicides with luminal agents in intestinal amoebiasis.
- Giardiasis often occurs in children and travellers.
- Abstinence from alcohol is necessary during metronidazole therapy.
Detailed Notes:
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