The Effectiveness of Metronidazole, Praziquantel and Co- Trimoxazole on Blastocystis hoMinis *Nadham K. Mahdi, M.Sc., Ph.D. **Sarkis K. Strak, F.R.C.P. Abstractِ : Objective: To investigate the pathogenicity of Blastocystis hominis in man and its proper chemotherapy. Methods: Patients who had only Blastocystis hominis and no other parasites or enteric bacteria were allocated into one of. What first-line treatments are available for Blastocystis ‘hominis’ infection? Metronidazole is usually listed as a first-line treatment for Blastocystis. Parasitology. Life cycle. B. hominis is an anerobic protozoan parasite that inhabits the gastrointestinal tract of humans. The organism has four different distinct parasite forms-the cyst forms, the ameboid forms, the granular forms and the vacuolar forms. Although metronidazole is often prescribed for Blastocystis infections, there is conflicting reports on its efficacy. Even in combination with a luminal agent, such as paromomycin, Blastocystis eradication cannot be guaranteed. If you want to attempt a Blastocystis hominis eradication protocol, I'd suggest first checking what the percentage eradication rate is for the protocol you are using. Single drug treatments such as metronidazole (Flagyl) have a poor success rate. KEY WORDS: Blastocystis hominis, metronidazole, nitazoxanide, trimethoprim-sulfamethoxazole INTRODUCTION Blastocystis presents a great challenge to 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.[ 1 ] It is quite possible that patients who respond to treatment for Blastocystis with metronidazole or trimethoprim-sulfamethoxazole (TMP-SMX) may actually have clinical improvement owing to treatment of a secondary pathogen. Treatment. The clinical significance of Blastocystis spp. is controversial. Treatment with metronidazole* at various doses has been reported, for example (adults): Ma derniere dose de Flagyl etait hier matin (500mg), le sentiment de ''pression'' au niveau des abdos est parti graduellement, cependant j'ai deja remarqué un retour de ballonement hier soir quoique pas mechant. En cas d'antécédents de troubles hématologiques, de traitement à forte dose et/ou de traitement prolongé, il est recommandé de pratiquer régulièrement des examens sanguins, particulièrement le contrôle de la formule leucocytaire.