Treatment Options for the Eradication of Intestinal Protozoa

Michael JG Farthing


Nat Clin Pract Gastroenterol Hepatol. 2006;3(8) 

In This Article

Blastocystis Hominis and Other Species

Blastocystis hominis has presented a great challenge for biologists seeking to describe its taxonomy and for parasitologists and clinicians who have struggled for many decades to determine whether it is truly an enteropathogen.[72] Current evidence indicates that although this organism (like many of the other protozoa) can coexist with its human host without causing diarrheal disease,[73] it can also be associated with acute and chronic diarrhea, and seems to be more prevalent in immunocompromised individuals.[72,74,75,76] The epidemiology of B. hominis has been incompletely described, but it is almost certainly transmitted by the fecal–oral route. The organism has also been linked to the presence of overt symptoms in patients with irritable bowel syndrome.

The majority of reports on the effect of antimicrobial chemotherapy for B. hominis infection are either case reports or small, noncontrolled studies.[72] Several studies conducted during the past 5 years indicate, however, that metronidazole 800 mg three times daily for 5–10 days is effective in some patients, although the paucity of information means that the accurate prediction of a response is difficult in individual patients.[77] Co-trimoxazole in standard doses (sulfamethoxazole 800 mg and trimethoprim 160 mg, twice daily for 7 days) is, however, reported to eradicate the organism in more than 90% of infected, symptomatic individuals.[78] Numerous other antiprotozoan componds have been tested, with variable results, but perhaps the most promising new drug is nitazoxanide. A placebo-controlled trial of nitazoxanide 500 mg twice daily for 3 days reported a clinical and parasitological cure rate of 86%.[79]


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