Enterotomy and phenobarbital

[Rev.mim@hotmail.com]

My 7 year old lab was doing well with a regimen of phenobarbital and zonisimide. He underwent a foreign body removal surgery 12/3/2017.
On 4/1/18 he had a second emergency surgery for a twisted small intestine from an adhesion. At this time 4 feet of his jejunum was removed. Is there anyone who has had success with phenobarbital following such a large resection? His peak and trough levels of phenobarbital are still too high (36 and 34) after decreasing his dosage by 1/3. The vet is monitoring him closely, but I was hoping someone had a similar experience and could offer encouragement.