Dientamoeba Fragilis Infection Medication

Updated: Jul 31, 2018
  • Author: Maria A Garcia Fernandez, MD; Chief Editor: Russell W Steele, MD  more...
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Medication Summary

The goal of therapy is eradication of the parasite Dientamoeba fragilis. The drugs used are considered investigational by the US Food and Drug Administration because of a lack of clinical trials. Response rates for a single course of therapy are 70-90% in the limited data published, with higher rates of treatment failures reported following the use of metronidazole as compared with other antimicrobials. There is no consensus as to best clinical practice due to lack of large-scale, randomized trials. A 2014 randomized study found no evidence to support routine metronidazole treatment of D. fragilis –positive children with chronic gastrointestinal symptoms. [11]

A study reported that exposure to metronidazole was found to confer decreased risk of D. fragilis infection; however, similar associations were found for antimicrobials not commonly used to treat D. fragilis, such as broad-spectrum penicillin, fluoroquinolones, and macrolides. In contrast, mebendazole exposure was associated with increased risk. [12]

A study by Boga et al suggested that in patients with D. fragilis infection, coinfection with E vermicularis may somehow protect D. fragilis from eradication by drug therapy. If so, according to the investigators, this would indicate that patients coinfected with the two parasites should be treated for both simultaneously. [13]  Current recommendations for therapy include one of the following drugs: iodoquinol (drug of choice), tetracycline, paromomycin or metronidazole. Availability of iodoquinol and paromomycin in the United States is limited. Newer agents secnidazole and ornidazole appear effective in single dosage with fewer side effects and longer half-lives while ronidazole, tinidazole and nitazoxanide show in vitro activity against D. fragilis. [14, 15, 16, 17]



Class Summary

Parasite biochemical pathways are different from the human host; thus, toxicity is directed to the parasite, egg, or larvae. Mechanism of action varies within the drug class. Antiparasitic actions may include the following:

1. Inhibition of microtubules, causing irreversible block of glucose uptake

2. Tubulin polymerization inhibition

3. Depolarizing neuromuscular blockade

4. Cholinesterase inhibition

5. Increased cell membrane permeability, resulting in intracellular calcium loss

6. Vacuolization of the schistosome tegument

7. Increased cell membrane permeability to chloride ions via chloride channels alteration

Metronidazole (Flagyl)

Imidazole ring-based antibiotic active against various anaerobic bacteria and protozoa.

Tetracycline (Sumycin)

Inhibits bacterial protein synthesis by binding with 30S and, possibly, 50S ribosomal subunits.

Iodoquinol (Yodoxin)

Amebicide used in treatment of D fragilis.

Paromomycin (Humatin)

Amebicidal and antibacterial aminoglycoside obtained from strain of Streptomyces rimosus; active in intestinal amebiasis.