What is the role of medications in the treatment of Dientamoeba fragilis infection?

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

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