Antiamoebic Drugs: Types, Uses, and Mechanisms Explained

Antiamoebic Drugs: Types, Uses, and Mechanisms Explained

Describe Antiamoebic Drugs.
Answer:

Antiamoebic Drugs Chloroquine

Chloroquine kills trophozoites of E. histolytica and is highly concentrated in the liver. Therefore, it is used in hepatic amoebiasis only.

Because it is completely absorbed from the upper intestine and not so highly concentrated in the intestinal wall it is neither effective in invasive dysentery nor in controlling the luminal cycle (cyst passers).

For amoebic liver abscess, chloroquine is sometimes given along with or immediately after a course of metronidazole to ensure complete eradication of the trophozoites in the liver.

A luminal amoebicide must always be given with or after chloroquine to abolish the luminal cycle.

Antiamoebic Drugs Diloxanide Fuorate

It is a highly effective luminal amoebicide that directly kills tropho- zones responsible for the production of cysts. The furoate ester is hydrolyzed in the intestine and the released diloxanide is largely absorbed.

Diloxanide is a weaker amoebicide than its furoate ester, no systemic antiamoebic activity is evident despite its absorption. Diloxanide furoate exerts no antibacterial action.

lt is less effective in invasive amoebic dysentery, because of poor tissue amoebicidal action. However, it has produced high cure rates in mild intestinal amoebiasis and in asymptomatic cyst passers.

Diloxanide furoate is very well tolerated; the only side effects are flatulence, occasional nausea, itching, and rarely urticaria.

Antiamoebic Drugs Nitazoxanide

This congener of the anti-tapeworm drug niclosamide has been introduced for the treatment of giardiasis but is useful in amoebic dysentery and cryptosporidiosis also. Its active metabolite acts by inhibiting the enzyme pyruvate: ferredoxin oxidoreductase (PFOR) in the parasite.

Antiamoebic Drugs: Types, Mechanism of Action, and Clinical Uses

Antiamoebic Drugs 8-Hydroxyquinolines

8-hydroxyquinolines were widely employed in the past. All have similar properties; are active against Entamoeba, Giardia, Trichomonas, some fungi, and some bacteria fungi (dermatophytes, Candida) and some bacteria.

They kill cyst-forming trophozoites in the intestine but do not have tissue amoebicidal action. They afford relief in chronic intestinal amoebiasis.

Their efficacy in eradicating- ing cysts from asymptomatic carriers is rated lower than that of diloxanide furoate and they are totally valueless in extraintestinal amoebiasis.

Antiamoebic Drugs Tetracyclines

They directly inhibit amoebae only at high concentrations. The older tetracyclines are incompletely absorbed in the small intestine, reach the colon in large amounts and inhibit the bacterial flora with which Entamoeba live symbiotically.

Thus, they indirectly reduce the proliferation of entamoeba in the colon and are especially valuable in chronic, difficult-to-treat cases with only the luminal cycle and little mucosal invasion.

Common Antiamoebic Drugs: Metronidazole, Tinidazole, and More

Antiamoebic Drugs Emetine

• Emetine is a potent amoebicide and kills trophozoites but has no effect on cysts. It acts by inhibiting protein synthesis in amoebae by arresting intraribosomal translocation of the tRNA amino acid complex. In acute dysentery the stool is rapidly cleared of the trophozoites and symptomatic relief occurs in 1–3 days. It is highly efficacious in amoebic liver abscesses also.
• Emetine cannot be given orally because it will be vomited out. It is administered by SC or IM injection.