I would suggest not to , though it is recommended by few .Loose motions - watery , not blood tinged , without any fever
or abdominal pain
is usually caused by viruses (most common cause) so antibiotic is of no use.
The right treatment would be to replenish the lost fluid , in form of Oral rehydration solution - in the dose 10 ml per KG for every losse motion passed.
Then continue normal soft diet
with out much spices.
If he has fever or abdominal pain or blood streak in stool , then u r justified in using Power Gyl , which is an antibiotic solution.
Hope this helps...Wish a speedy recovery.