Thank you for the query.
You should follow as advised by your doctor. Septrin is an antibiotic used for bacterial infection of the intestines and if your doctor decided to prescribe it, he must have seen indication for it. Darolac is a probiotic
and you should take both Septrin and Darolac (please note that there should be a about 30 minutes of break between this two medicines).
If your diarrhea
wont improve in 48 hours, it is necessary to get back to your doctor and have stool tests performed.
Hope this will help.