Just called my vet because I know they were discussing this not so long ago. Here is what I was told.
Anapryl is used (it is also used in Cushings) ... It is very expensive. They have recommended the generic form (Selegiline) but have been having problems finding it.
Anipryl® - Help for senior dogs and cats with dementia or cognitive dysfunction?
Also....Hill's Science Diet makes B/D which is also for aging dogs. I know a lot of people don't like Hill's and I don't like many of their products, BUT I do know that some of them do work! They do a lot of research on their products. Don't know that it would hurt to try it.
b/dŽ Canine Aging & Alertness - Dry