Flagyl, metronidazole, is commonly prescribed by veterinarians to treat diarrhea of unknown cause. The crazy thing is that veterinarians are not even 100% sure how metronidazole works to control diarrhea. They just know that somehow it takes care of a diarrhea issue....
If your cat is also vomiting, call your vet immediately. You may need different medicine or your kitty may have a bigger problem. If your cat is not vomiting and is pooping the normal 1-2 times a day but the stool is soft, consider a probiotic 2-4 hours after...