Hi, welcome to healthcare magic forum. i understand your query as well concern about your child's health.
As he is having loose stool
with blood streaks, it suggests there is mixed ( both protozoal & bacterial) infection in his stomach. So along with flagyl
syrup he requires some antibiotics also.I usually prescribe my patients syrup- Ciplox
1.5 ml twice daily along with ORS
If symptoms will still not subside then consult your doctor soon. He may require hospital admission.
Wish your child good health .