Side effects of Phenytoin

My husband has been on Phenytoin for thirty years, he says that he constantly feels heady. Itis difficult to describe this but here goes.it is a sensation of pressure across the front of his head and face,it also a sensation of heaviness and fogginess, he feels lethargic and has to force himself into action. Sometimes it decreases but it is worse with exertion. It never goes completely. The only time that he was free from it was twenty three years ago when he stopped taking phenytoin for three years. He takes three capsules of 100 mg a day. His doctor monitored his blood level and recommended 280 mgs a day which is not possible to obtain.

I do hope you can shed some light on this as he tries very hard to ignore this problem.We have stopped his caffeine intake and given up his glass of wine, we watch his sugar levels in case it is that but nothing appears to help. He is 60 years old, extremely fit and a marine engineer by trade, he is still working and his hobby is the restoration of lantern and turret clocks and bee keeping.

thank you