I have constipation due to amebea and have to take Flagyl 400 for 5 days. This reoccurs after every month. Is there alternate way out a permanent one?

GI. Yes...You need a more thorough work-up; start with your primary care physician...And you'll probably need a gastroenterology evaluation.
Find the source. It is very important to find the source of the parasite. Prevention is much more affective than the cure. It's safer too. Agricept is an otc preparation that can help with parasites too.