Treatment Information

What first-line treatments are available for Blastocystis ‘hominis’ infection?
Metronidazole is usually listed as a first-line treatment for Blastocystis.  A recent review on e-medicine listed dosages and duration for metronidazole and several other drugs.

What other treatments are available for Blastocystis ‘hominis’?
A recent review published in the Journal of Digestive Science included a comprehensive list of treatments reported to be successful in Blastocystis infection over the last 10 years. Drugs included TMP-SMX, rifaximin, Nitazoxanide, and others.  However the review noted that those studies did not use reliable methods for detecting Blastocystis infection to establish eradication of the organism.  As such, it is difficult to know how often the drug eradicated the infection vs. how often it produced temporary symptomatic improvement.

Several papers have reported success in treating patients who had failed metrondizaole therapy.  The largest study (n=50) was conducted in Australia using a combination therapy of secnidazole, nitazoxanide, and furazolidone, and reported in a 2007 Reuters Health article..  A Los Angeles gastroenterologist reported success with the use of Nitazoxanide, reported in a2010 abstract from the American Gastroenterological Association..  A report from Germany indicated that combination therapy with metronidazole and paromycin was effective in a case of refractory long-term Blastocystis infection acquired in association with international travel.

Why don’t the Blastocystis ‘hominis’ treatments work?
   Antimicrobials work by inhibiting the activty of microbes, allowing the host’s immune system to eliminate them.  Antimicrobials can also work by killing the microbes.  Antimicrobials may fail to work against specific microbes if they do not have sufficient activity against the organism, or because the inhibition provided by the antimicrobial is insufficient to allow the host to clear the organism.
There is a remarkably lack of in-vitro study of Blastocystis.  However, the studies available suggest that certain isolates of Blastocystis will not respond to metronidazole.

What can be done for patients when treatments don’t work?
Many patients report improvement with elaborate exclusion diets, which usually include avoiding sugar, coffee, tea, soda, frut, wheat, rice, corn, red meat, processed foods, breakfast cereals, and high carbohydrate foods.  Because there is extensive overlap between irritable bowel syndrome (IBS) patinets, and Blastocystis patients, treatments to reduce the symptoms of IBS may be effective in Blastocystis infection.


1. Stein, Jill.  Drug Combination Promising for Enteric Parasite Infections.  Reuters Health,  November 1, 2007.

2. Yakoob J, Jafri W, Jafri N, Islam M, Asim Beg M. In vitro susceptibility of Blastocystis hominis isolated from patients with irritable bowel syndrome. Br J Biomed Sci. 2004;61(2):75-7.PMID: 15250669

3. Dunn LA, Boreham PF. The in-vitro activity of drugs against Blastocystis hominis. J Antimicrob Chemother. 1991 Apr;27(4):507-16.PMID: 1856129

4. Haresh K, Suresh K, Khairul Anus A, Saminathan S. Isolate resistance of Blastocystis hominis to metronidazole. Trop Med Int Health. 1999 Apr;4(4):274-7.PMID: 10357863

5. Vogelberg C, Stensvold CR, Monecke S, Ditzen A, Stopsack K, Heinrich-Gräfe U, Pöhlmann C. Blastocystis sp. subtype 2 detection during recurrence of gastrointestinal and urticarial symptoms. Parasitol Int. 2010 Sep;59(3):469-71. Epub 2010 Apr 2.PMID: 20363362

This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the disease described above or think that you may have a parasitic infection, consult a health care provider.

BRF distributes information concerning developments in Blastocystis research.  We also conduct and coordinate research, and we share those results after they are accepted to such journals.  We may share information communicated by patients about their cases with their permission, without providing identifying information about the patient..  We can not diagnose you, provide treatment, or manage your particular medical case.  Please contact a physician for health care advise.