In case anyone else has this problem, I want my experience to be available to them. There was very little to read on the DURATION of initial phenobarbital side effects on the web, and I was very frightened by what I saw. So, here's what happened with my dog.
The side effects (which were severe) or
: #dae8f4'>lasted approximately three weeks. It is possible that they or
: #dae8f4'>can or
: #dae8f4'>last this long. Most people say they go away in a day or
two, but in very sensitive dogs, it takes much longer.