Suggest Antibiotics For Babies Passing Frequent And Greenish Stools

Doctors hav recommended Zinconia syrup for my 3 month old twins who hav been passing frequent greenish stools after every feed and almost 10-12 times a day for past 2 weeks. How effective it is? Kids have shown no improvement at all. Arent there any anti biotics to stop this passing of frequent stools for 3 month old kids? Do they have to be admitted to get the antibiotics via IV???Please help.