Dilantin can cause drowsiness & insomnia, along w/stomach problems, loss of appetite, weight loss, etc. It could be making her weak or it could be the progress of the disease, your doc should know. I'd suggest you, and everyone else, buy a current drug book so you can easily look up interactions, side effects, what foods, supplements or activities to avoid, etc. Especially with AD, there are often so many drugs for the AD & other conditions a patient may have. Good luck, hope she gets her strength back.