ok thank you for that information. Phenobarbital is known to cause lethargy/sluggishness but usually subsides within a few weeks of starting the meds. I am worried though to have you stop the meds because phenobarb takes 2-3 weeks to get to steady state blood levels so we typically want to add another med in while we wean off the phenobarb so that we reduce the risk of seizures. phenobarb is very sensitive and often we see break through seizures if you stop the meds. the dose seems appropriate and is on the lower end of dosing, so I don't think that we are dealing with too much drug. However, it may not be the best drug for him. I know you said you have an appt in a week with the vet, but I would really try to get him in tomorrow to discuss maybe changing the phenobarb to another drug. (I like keppr ER, it has much less side effects, safer, forgiving if you miss a dose, but a little more expensive. I have found if you have a plus membership at sams club it is much cheaper and comparable to other meds) there is also zonisamide. bromide is another option but often when given with the phenobarb makes the side effects worse (more sluggish, can see increased peeing and drinking, increased appetite, weak in the back end).
it sounds like either we may have gotten into something, or maybe the drug isn't the best option for him, or may be something completely different. however, I don't think it is a good idea to stop the med without seeing the vet and starting something else as we dont' want to set off series of seizures.
I would maybe try to give some famotidine (generic store brand for pepcid walgreens/walmart, etc). i would give 20mg regular strength every 12 hours on empty stomach (1 hour before food) and try a bland diet of boiled chicken and rice, no seasoning, nothing added, etc. i would try to get into the vet asap to discuss further treatment or testing once able to do physical exam and make sure nothing else going on.
certainly if you see the lethargy worsen, starts vomiting, has a seizure, pale gums, etc want to get him seen asap.
does that make sense? do you have other questions for me?