Hi there! I got this from
Phenobarbital
PB (Phenobarbital) side effects in dogs are "sedation, lethargy, excessive urination, excessive thirst and excessive hunger, hyperexcitability, ataxia (loss of coordination or hind end weakness) and restlessness. Most of these side effects diminish or disappear after the first few weeks of therapy. Excessive urination, excessive thirst and excessive hunger are the most common long-term side effects."
Hope this one helps!