I have never seen Flagyl cause mucus. You need to call your vet and them know that he lethargic. Because that could be nother symptom.
Give him lots of snuggles and keep him warm.
Sometimes if it is a virus, you just have make sure he stays hydrated, warm and that his sugar is ok. But lethargy could be a sign that he is getting a little bit more dehydrated, so I would let your vet know.
HUGS!!
Kate |