Metronidazole was prescribed for 3.5 lb poodle (14 yr old) for colitis. She did well from May 15 until December when she started developing neurological symptoms associated with metronidazole. When I withdrew the drug, the neuro problems subsided but the colitis came back. I was working on a balance with fiber in diet and no metro when I took her in to our Vet. After examining her and hearing from us she said it was unlikely that the metro was giving her problems since she had been on it so long, even though I told her I thought it was building to a toxic level. She instructed me to give her the usual dose at Noon that day, which I did and my little poodle was dead by 2:00. My vet had closed for the day and I was instructed to take her to a nearby city (we are in a rural area) and of course we didn't make it in time. Please be aware that the toxicity may build up over time and be alert to all of the side effects that may be caused by this drug. And listen to your gut. I didn't and I am heartbroken and unable to get this out of my mind.