Again I will model the blastocystis research concerning treatment approaches. The best guide I can find is badbugs.org. Blastocystis (b. hominis) is a diverse parasite that rarely responds to Flagyl even though it has been considered the 'gold standard' of protozoa drug treatments. Part of the problem with blastocystis is that it has several forms and each form requires a different drug strategy.
I am listing some of the combinations:
1st protocol of the triple drug cocktail:
2nd protocol of the triple drug cocktail
2nd protcol is a revised version of the 1st having less side-effects probably from removing Furoxone as the lumicidal drug and replacing it with Diloxanide Furoate.
Secnidazole/Septrin (Septra)/Dioloxanide Furoate
Other combinations listed on badbugs:
Rifaximin with Nitazoxanide
Flagyl with Iodoquinol