I used the badbugs.org site when I had Dientamoeba fragilis a few years back. I know Blasto is harder to eradicate. I have just had a look to see what Jackie is advising these days about Blasto treatment
http://www.badbugs.org/Blastocystis_hominis/bh_treatment2.htm

It bothers me that Case 4 appears to have tried the same Flagyl/Metronidazole prescription dose your doctor suggests.

I took Flagyl several times (standard Doctor’s recommendation). At the time he thought I had giardia. Of course it didn’t work. I didn’t take a particularly high dose. Later I tested positive to DF and took the 2 drugs recommended on the badbugs site for DF. I was extremely apprehensive but I went ahead anyway. For me the intermittent diarrhea was worse than anything. All I can say is that was about 6 years ago now and I NEVER EVER have diarrhea again. I even feel I could eat off food and not get diarrhea. BUT and it is a big BUT I have constipation and bloating instead and I have not been able to resolve that. Sometimes I think it is worse than having diarrhea. So, the question is, did those strong drugs damage my gut/did the parasite cause lasting damage/ or have I another parasite like Blasto? (I did test clear of DF after the treatment) Who knows?

The treatment I took was for an arduous 20 days. Jackie was recommending the 10 day treatment for Blasto of Nitazoxinide/Secnidazole/Furazolidone though this was in 2005 and it might have changed now. I certainly felt far worse taking Flagyl than Iodoquinol and Doxycycline (drugs specifically for DF). It is hard to advise you and probably not appropriate but the truth is that you do not want to take meds more than once so if it was me I would take the triple dose. That is, if you feel so sick that you must take meds. Don’t rule out herbs. I routinely do a herbal parasite cleanse once or twice a year. I have had periods when I have felt really well, especially when taking Chinese medicine for example. I suggest that the routine use of herbal medicine seems to work. It might be slow but less arduous. these amoebas).

ADVICE:
I did colonics before, during and after treatment. This made a huge difference to how I coped with taking the drugs.
I think it is VITAL do treatment over the full moon.
Very important to avoid probiotics when treating amoebas. Any kind of probiotic (especially kefir) will set me back