I can't straight out say what the maximum dose is that your dog can receive. This depends on their metabolism and tollerance for the drug. I will say that the veterinary drug formulary says this - Initially, 2-4 mg/kg PO divided into 2-3 doses per day. If ineffective, may increase in a stepwise fashion to a maximum of 18-20 mg/kg/day.
I am trying to find out what "lethal" dose is rather than general dosage.
I believe my dog died because of too much Phenobarbital, and I have not been able to sleep at all for a week. I really need to know this to have any kind of resolution.