Therefore, it is suggested that metronidazole may be ineffective in achieving complete eradication possibly due to resistance.

IBS and control cases positive for B.hominis were treated with 1,200mg of metronidazole daily for 7 days and the stool was reinvestigated for B.hominis. The results show that B.hominis infection in IBS patients could not be fully cured using standard treatment (1,200mg of metronidazole daily for 7 days).
Blastocystis hominis infection in irritable bowel syndrome patients. Tungtrongchitr A Southeast Asian J Trop Med Public Health. 2004 Sep;35(3):705-10.

"B. hominis resistance to furazolidone, metronidazole and ciprofloxacin at 0.01 mg/mL was 32% (8/25), 40% (10/25) and 100% (25/25), respectively. B. hominis isolates varied in their degree of susceptibility to the three drugs studied, being greater with furazolidone than with metronidazole, and complete resistance with ciprofloxacin."
Br J Biomed Sci. 2004;61(2):75-7.

The study shows that isolates of B. hominis of different geographical origin have different levels of resistance to metronidazole. The search for more effective drugs to eliminate th parasite appears inevitable, especially since surviving parasites from metronidazole cultures show greater ability to multiply in subcultures than controls.
Isolate resistance of Blastocystis hominis to metronidazole.
Haresh K, Suresh K, Khairul Anus A, Saminathan S.
Trop Med Int Health. 1999 Apr;4(4):274-7.

Through anecdotal reports, it has become evident that there are a significant number of treatment failures with metronidazole.
Blastocystis hominis - Past and Future
C.H. Zierdt
Clinical Micro. Reviews. Jan 1991 Vol 4, No 1; 61-79

If treatment appears warranted, metronidazole is suggested as the drug of choice, although failures of this drug in eradicating the organism have been reported.
Stenzel DJ, Boreham PF.
Blastocystis hominis revisited.
Clin Microbiol Rev 1996 Oct;9(4):563-84

Blastocystis hominis cysts concentrated from faeces were resistant to metronidazole up to a concentration of 5 mg/ml. A cysticidal drug is therefore needed for radical treatment, to avoid relapse and to prevent transmission.
Resistance of Blastocystis hominis cysts to metronidazole.
Zaman V, et al
Trop Med Int Health 1996 Oct;1(5):677-8

Metronidazole effectively relieved the symptoms and cleared the organism in some but not all patients.
Blastocystis hominis infection: signs and symptoms in patients at Wilford Hall Medical Center.
Mil Med 1990 Sep;155(9):394-6
Wilson KW, et al

All stool samples were microscopically examined, 28 were discharging large numbers of parasites before treatment. Of 28 severely infected individuals, 12 were treated with metronidazole/250-750 mg at a regimen of 3 x/day/10 days and 4 of the 12 were eradicated. Nine individuals were treated with TMP/SMX/1 tab at a regimen of 3 x/day/10 days and 2 of the 9 were eradicated. For severe B. hominis infections, it appears that metronidazole and TMP/SMX are effective in some individuals, but not all.
Blastocystis hominis and the evaluation of efficacy of metronidazole and trimethoprim/sulfamethoxazole.
Parasitol Res. 2005 Jun;96(4):273-5. Epub 2005 May 25. Moghaddam DD et al.

"Thank-you so much for providing such fantastic information on your website. It is the only beacon of light I've seen in a very long time. I am hoping you can send information on how to obtain the triple therapy treatment in Canada? I have seen no less than 30 doctors in Canada over the past 4 years and no one will even let me finish my sentence when I ask if b hominis is behind all this. I've done a course of metronidazole, felt better for about a month or two, but am now back to square one. I can't live like this any longer and to say I'm desperate is an understatement. I'm totally sick and miserable and keep getting judged by everyone. They all think I'm making it up. I'm pretty sure I picked it up in Thailand." (Canada 2016)

"The problem is they are rather in the dark ages in Queensland and not accepting of the condition (B.hominis).  One doctor did not even want to test my son (who has the same symptoms) after I tested positive and refused to test my husband. My son tested positive and was given Flagyl."  (July 2015. Australia.)


"After suffering for some time with this, I eventually found out I had Blasto. I went to 3 infectious diseases doctors in the US and either they wrote it off or they have no idea about bugs (that's real scarey). It really is a shame that doctors here wouldn't even entertain the thought that it could be a possible problem. I mean really what could it hurt to try". (USA. Jan 2015)


"I saw a gastroenterologist and he told me to try Flagyl and if that didn't work it was probably IBS and that I should stick to a LOW FODMAP diet. I am so horrified that GPs and specialists where I am from (and also around the world as I've read) choose not to help their patients. Its a complete lack of "duty of care".

(Tasmania, Australia. Jan 2015)

"Thank you for sending the info for treatment of Blasto. That said I'm having a few problems finding a g.p. who will give me a prescription for them. Every g.p. I have been to has been difficult and treated me like an idiot. They haven't heard of the drug combo, also they tell me that flagyl is the best treatment and will get rid of Blasto in a couple of days and that Blasto will just go away by itself anyway. One even said he would write me out a prescription for 'eye of newt' and told me i was being given imaginary drugs.". (USA. Jan 2006)



The unfortunate thing is that most GPs will give a course of metronidazole which only makes things worse. Professor Tom Borody, founder of the Centre for Digestive Diseases. Australian Doctor Magazine. 5 June 2015.

From these studies though, it is apparent that different subtypes show different susceptibility patterns and that metronidazole is not the most effective treatment for Blastocystis infection. In Vitro Antimicrobial Susceptibility Patterns of Blastocystis. Antimicrobial Agents and Chemotherapy. August 2015 Volume 59 Number 8. T. Roberts et al.

Metro. should no longer be considered the first line treatment therapy prescribed. Treatment failures in chronic Blasto. infection. Roberts et al. Journal of Medical Microbiology 2014.

Flagyl is the most commonly prescribed drug to treat Blasto. and D.fragilis. Warnings about significant Flagyl treatment failures first appeared in the medical literature in 1991:

Through anecdotal reports, it has become evident that there are a significant number of treatment failures with metronidazole. Blastocystis hominis Past & Future. Clinic Micro Reviews. C.H. Zierdt. Jan 1991.

Unfortunately much of the Blasto. research was ignored for decades which resulted in many people being exposed to Flagyl unnecessarily:

My doctor has treated me for my blastocystis hominis infection with flagyl, and it has not worked. My diagnosis was this last July, and I have been struggling to even convince my doctors that this is something worth treating! (March 2016. USA)

"I was prescribed flagyl (metronidazole) 4 days ago. Unfortunately my symptoms have only gotten worse. My nausea is constant and I can hardly walk around because the headaches are so bad. I was suppose to start university today, but am unable to attend." (2013)

From the mother of an 8 year old with Blasto: "I was told by my doctor after the positive result for Blasto that it was not something that would be causing her her symptoms but she would treat it anyway, "in case", with Flagyl". (Nov 2014)

"My specialist advised that he usually prescribes a course of metronidazole and if it doesn't go away, just forget about it - I'm pretty unimpressed and paid $160 per consult for that little pearl of wisdom." Australian with B.hominis. (October 2002. Australia)

"We saw Dr X, infectious disease physician, who feels most of our symptoms are reflective of panic/anxiety disorder and has given us the option of seeing a colleague of his (a shrink) to discuss my physical state in relation to emotions/stress/worry etc. Is finding help meant to be this complicated and confusing?". Australian woman trying to find medical help for herself and her two children diagnosed with Blasto. Jan. 2006


Good reasons to avoid Flagyl:

Most of Flagyl is absorbed into the small intestine. The large intestine, where Blasto. and D.fragilis reside, receive only low concentrations of this drug.

Flagyl is a broad spectrum antibiotic which kills off more susceptible beneficial GI bacteria that can prevent opportunistic pathogens (like Blasto. and D.fragilis) from colonising more of the bowel, which probably explains this problem:

"I first became ill around 18 months ago. My symptoms included stomach pains loose bowel movements and nausea. The GP gave me pills to reduce stomach acid and told me I might have IBS and not to worry as the symptoms would go away given time. I explained my symptoms to a naturopath who told me straight up "You have a parasite" She gave me some herbal medicine that initially helped but soon after I ceased taking the herbs the symptoms returned. I changed GPs and a stool test found that I had (high levels of) D.fragilis. Three courses of Flagyl later I not only still had D.fragilis I also now had the blastocystis appear in my stool test." (October 2005)

At first the doctors only diagnosed me with D. fragilis, but after two Flagyl treatments failed to eradicate the D. fragilis they also discovered B. hominis in my follow-up stool samples (three taken every other day).
(February 2015 USA)

After 5 months of skin rush and itching, I was diagnosed carrying Blasto. and D.fragilis. I've seen 3 dermatologists who diagnosed me with Urticaria and stress. My doctor even tried to give me some anti-anxiety pills. I couldn't get anyone here in Israel to believe me or understand about Blastocyctis. After treatment with 15 days of Flagyl and 10 days of TMP-SMX, I'm still positive to Blasto. and now positive to D.fragilis. (July 2015 Israel)

Better treatment options:

The Triple Therapy

In 2001 the anecdotal and scientific evidence on this site convinced Professor Tom Borody at the Centre for Digestive Diseases ( that D.fragilis and Blasto. are potential pathogens — an extremely contentious theory at the time — and still is.

The triple therapy evolved out of years of experimental treatments where various drugs recommended in the Blasto. literature were combined to achieve a much higher cure rate than using Flagyl alone.

The success of the triple therapy lies in combining luminal drugs with systemically absorbed drugs to kill both the cysts and embedded parasites. Luminal drugs are minimally absorbed and work by killing (the parasite) on contact.

The CDD's current treatment for Blasto:

Secnidazole 400 mg (30 Capsules) 3 times a day
Diloxanide Furoate 500mg (30 Capsules) 3 times a day
Septrin Forte (20 Tablets) 2 times a day
all for 10 days.

Their secondary treatment for more treatment resistant Blasto.:

Secnidazole 400 mg (30 Capsules) 3 times a day
Furazolidone 100 mg (30 Capsules) 3 times a day
Nitazoxanide 500 mg (20 Capsules) 2 times a day
all combined for 10 days.

Contact me for the treatment sheet.

If you are still testing positive after the triple, or perhaps you are too unwell to try the oral treatment, then consider undergoing the CDD's rectal infusion of Blasto. meds. They have success with previously untreatable Blasto. using this method. Website: A medical study about this procedure here.

Drug availability:

One of the biggest hurdles for patients trying to overcome Blasto. is sourcing the meds used in the triple therapies. Because Blasto. has been ignored for so long by the medical community many of the drugs used by the CDD to treat Blasto. are not available to patients outside of Australia. For instance furazolidone, diloxinide furoate and secnidazole are unavailable in the UK and other European countries, US, Israel, Russia etc. Some people are sourcing these meds online from This is NOT a recommendation. Please read my disclaimer.

Despite the unavailability of these meds in the UK, there is one UK doctor who sources these meds from Australia and prescribes the CDD's treatments via Skype for overseas patients:

Dr Apelles Econs

Thames Allergy Centres

The Health Suite, Rooms 14/16

28 Queens Road


Surrey KT13 9UT

prescribes Blasto. meds via pre-booked phone apptment.

The initial one hour consultation is £175.00 whether face to face, skype or telephone. The meds for BH are approximately £300 + P&P and for D.fragilis it is usually about £80 + P&P.

"I guess my main problem is my doc is not willing to prescribe the triple therapy. I've asked on three occasions and he's said no every time." Sept. 2003, Canberra, Australia.

Where to buy the meds in Australia:

In Australia the meds are available, with a prescription, from:

Skinners Compounding Pharmacy, Lindfield, NSW. Australia


Sydney Compounding Chemist on (02) 9871 7533

You will need a doctor to sign-off on the treatment.

If you live outside of Australia please contact me.

Other treatment options:

From a study published in the medical journal Antimicrobial Agents and Chemotherapy (AAC) in May 2015:

Ivermectin and albendazole are commonly used antihelminth treatments. Neither of these drugs has previously been tested in vitro against Blastocystis. In this study, it was found that albendazole had a lethal concentration up to 250 g/ml and ivermectin had a lethal concentration up to 125 g/ml (Fig. 4), suggesting that taken in high doses these drugs are an option for treatment.
In vitro antimicrobial susceptibility patterns of Blastocystis. Antimicrob Agents Chemother. 59:4417– 4423. doi:10.1128/AAC.04832-14. Roberts T, Bush S, Ellis J, Harkness J, Stark D. 2015.

Other treatments - successes & failures reported to this site:

Nitazoxanide: I've been tracking the success of this drug since it became commercially available in 2004.

According to extensive site feedback Nitaz failures are more common than cures when prescribed alone.

Despite that, published drug studies show a very high cure rate with Nitaz and drugs like Flagyl) — that is until attention is paid to post treatment testing. Some studies base their outcomes on the results of a single unfixed stool sample which is less than 50% diagnostic. Apart from that false negatives can be a problem if the parasite colony hasn't recovered sufficiently to be detected in stool samples at the time of testing. Always best wait a minimum of 4-6 weeks before retesting after a drug treatment. If the results are negative but your symptoms are no better then retest using PCR or 3 fixed samples.

One of many examples from

Two hundred and forty-six adults and children infected with at least one protozoan and 2 helminths were given 7.5 mg/kg of nitazoxanide (500 mg to adults and 200 mg to children less than 12 years old) every 12 h for 3 consecutive days. Faecal samples were examined on days 6, 7, 8, 13, 14 and 15 (+/- 1) following initiation of treatment. Treatment with nitazoxanide was 71-100% effective in eliminating evidence of infection with Blastocystis hominis. Trans R Soc Trop Med Hyg. 1997 Nov-Dec;91(6):701-3.

More info. about the importance of specialised stool collecting and testing methods to diagnose Blasto. and D.fragilis here.

Flagyl and Bactrim (Septrin DS): This combo was the CDD's first treatment back in 2001. More effective than Flagyl alone, but not as good as the triple therapy. Worth trying if you are unable to obtain drugs used in the triple. Less likely to work if pre-treated with Flagyl.

This information is for educational purposes only. Please read my Disclaimer.