Side Effects Metronidazole Dogs. Drooling, blood in the urine and appetite loss are also possible but not as common. Side effects of flagyl in dogs.
Though it’s rare, some dogs may suffer from neurotoxic (nervous system) side effects, such as. Neurotoxic effects include encephalopathy, cerebellovestibular signs and periopheral neuropathy. Common side effects that might occur due to metronidazole one of the most common side effects which have been seen in the pets taking metronidazole is bad taste and gastrointestinal upset.