Hi Rach - It sounds a bit perplexing and I couldn't really say what it is. I wonder is it is something neurological? But it doesn't sound to me like a true emergency where he needs immediate attention and I would think it would be fine until his appointment. Does he seem to be in pain? Has he had any vomiting, diarrhoea, seizures? Anything else out of the ordinary? Is he walking strangely or holding his tummy rigid? Is there something unusual outside like a new cat in the area? Has he passed urine and faeces ok today? What is his gum colour like? It should be nice and pink unless he has darkly pigmented gums. What is his body temperature like? If you dont have a thermometer you can feel his ears. They can sometimes give you an indication of if he has a fever.
When was his phenobarb dosage last reviewed?