Pharmacology of Antiprotozoal Drugs: Treatment of Amebiasis

Flashcards covering the classification, mechanism of action, kinetics, and clinical uses of antiprotozoal drugs used for treating amebiasis.

Amebiasis

Also known as amebic dysentery, it is an infection of the intestinal tract caused by the organism Entamoeba histolytica.

Entamoeba histolytica

The causative organism of amebiasis that exists in two forms: invasive, fragile trophozoites and tough, infective cysts.

Trophozoites

The form of E. histolytica that causes invasion of the colon wall and ulceration, but is fragile and cannot survive outside the body.

Cysts

The tough and infective form of E. histolytica that survives outside the body and is ingested via contaminated food or water.

Luminal Amebicides

A group of drugs including Iodoquinol, Paromomycin, and Diloxanide furoate that act only within the bowel lumen.

Systemic Amebicides

Drugs such as Chloroquine, Emetine, and Dehydroemetine that act against amebas in the intestinal wall and liver only.

Mixed Amebicides

Drugs like Metronidazole and Tinidazole that act against E. histolytica in both the lumen and tissue.

LSM Rule

A mnemonic indicating drug action: Lumen stays Local, Systemic goes deep, and Mixed does both.

Metronidazole

The mixed amebicide of choice that kills trophozoites by forming reduced cytotoxic compounds that bind to proteins and DNA.

MAGIC Mnemonic

A mnemonic for Metronidazole clinical uses: Amebiasis, Giardiasis, anaerobic Infections (Bacteroides, cocci), and C. diff pseudomembranous colitis.

"No Metal Drinks" Mnemonic

A mnemonic for Metronidazole adverse effects: Nausea/GI distress, Metallic taste, and Disulfiram-like reaction with alcohol.

Disulfiram-like reaction

An adverse reaction characterized by flushing, palpitations, and severe nausea occurring when alcohol is consumed with Metronidazole.

Tinidazole

A second-generation nitroimidazole approved by the US FDA in 2004 that offers a shorter treatment course than metronidazole but at a higher cost.

Iodoquinol

A halogenated 8-hydroxyquinolone luminal amebicide used to clear asymptomatic carrier states; ADRs include rash, diarrhea, and peripheral neuropathy.

Paromomycin

An aminoglycoside antibiotic luminal amebicide that kills amebas by damaging cell membranes and reducing intestinal flora (their food source).

Chloroquine

A systemic amebicide used in combination with metronidazole to eliminate trophozoites in liver abscesses; also used as an antimalarial drug.

Emetine & Dehydroemetine

Systemic amebicides given IM for a maximum of $5$ days that inhibit protein synthesis by blocking chain elongation.

Phenobarbital interaction

An enzyme inducer that decreases the therapeutic levels of metronidazole.

Cimetidine interaction

An enzyme inhibitor that increases the half-life of metronidazole.

Asymptomatic cyst carrier treatment

Clinical scenario requiring only a luminal amebicide such as Iodoquinol or Paromomycin to clear the dormant infection.

Amebic liver abscess treatment

Clinical syndrome requiring a combination of Chloroquine + Metronidazole and/or Diloxanide furoate.