I know that this is a post from 2007 and I’m posting in 2021, but this is one of the top results if you google “red eyes dog phenobarbital,” and the original poster never clarified what was wrong with their dog. My dog suffered the EXACT same symptoms. My dog, who would have been 4 years old this year, was found to have lung cancer. The seizures were caused by the lung cancer, but the vet assumed idiopathic epilepsy because he lacked other symptoms and he was in the age range for idiopathic epilepsy. Though it seemed like the phenobarbital was the thing that was killing him, it was the undetected lung cancer all along. We tried to wean him off the phenobarbital as we thought that’s what the problem was, but he just kept getting worse and we discovered it was lung cancer, and he had to be put down that same day.
I hope this helps anyone else who comes across this post in the future. The phenobarbital may be causing lethargy, but the weight loss, seizures, red eyes, loss of motor function, diarrhea, are symptoms of lung cancer. Unfortunately, by this point it is likely incurable. I’d also like to add that if your dog is having seizures, even mild ones, request an x-ray to check for cancer along with the bloodwork that they’ll do first. If we’d had an x-ray done, he wouldn’t have suffered for two more months.
