Agree with LR...I'd be cautious about putting a young pup on too many meds without a clear need for it.
Pumpkin (plain, not the pie filling) can work
wonders for diarrhea, many vets will even suggest this.
Here's an awesome site; scroll down for some ideas for diarrhea:
http://www.bowchow.com/specific.html
Give that cute pup an extra hug from me!!