[Erinmay]

I googled Metronidazole and found this website:
http://www.wedgewoodpharmacy.com/monographs/metronidazole.asp

Side Effects
• Most common: clinical signs related to the bad taste, or GI upset.

• Dogs and cats: excessive salivation, gagging, regurgitation, pawing at the mouth, nausea, vomiting, and decreased appetite are the most frequent complaints. Less common or rare side effects include diarrhea, depression, lethargy, weakness, low white blood cell count, liver failure, and blood in the urine, or dark urine due to pigment changes. Neurologic signs may be seen after accidental overdose or, more commonly, with long-term moderate to high-dose therapy as in the treatment of difficult bacterial infections. Signs often begin 7 to 12 days following the start of treatment.

Precautions
• Metronidazole should not be used in young puppies and kittens.

• Metronidazole should be avoided or used with caution, at reduced doses, in animals with kidney or liver disease.

Jeez - maybe Maggie's too young for this? She's only 3 months...