I'm putting this in the main forum rather than in the Food group or Health group because it is so important for dog owners and especially new puppy owners to know this. Not all vets keep up with continuing education and new developments/research. It's up to us to educate ourselves. I've seen way too many doodle puppies who were unnecessarily given metronidazole go on to develop chronic digestive issues. Learn to speak up and question your vet, and say no to metronidazole!
Think metronidazole works? Maybe not so much
From the article:
There has never been strong evidence to support the use of metronidazole to treat acute idiopathic diarrhea for dogs, and the results of the first clinical trial evaluating this practice indicate it is probably not effective. This information should discourage the use of metronidazole as a treatment for acute diarrhea."