What medication was he put on? Does he have any other symptoms?
Has he ever had seizures before of did they start suddenly? How often is he having them?
Does your exotics vet see rabbits often? I would be worried about E. Cuniculi, or some sort of toxin poisoning, there are so many factors to think of that it’s impossible to know the cause without a proper examination. Maybe consider going for a second opinion, or discussing further with your vet.