St. Bernard having seizures

I have a six year old St. Bernard who had his first seizure two years
ago. Since that time, he has had a few off and on. Recently however,
his seizures have increased in frequency. A month ago he had two back
to back seizures and today he had four back to back seizures. I
brought him to the vet today and they are going to put him on
Phenobarbital.

The dog is my life and my buddy. My question is this. I've read so
much stuff about Phenobarbital and the harmful side effects, I'm
wondering if it's worth it to put him through it or should I put him
down? I love him with all my heart and soul and don't want to see him
suffer.

Any input would be greatly appreciated.