Constipation in Cats

I am writing on behalf of my dear wife who has a favored kitty (Alex) suffering from on and off constipation. At times the condition has been critical and we've been to the vet's for emergency unplugging.
My wife has tried several additions to the already expensive "Medical" specialty food he is on. These include everything from pumpkin to hemp seed and most recently psyllium.
If you have any thoughts on keeping Alex regular, we would appreciate it.

Much the same as in humans, regular bowel movements depend heavily on a diet suited to the individual and loaded in bioavailable nutrition. As your cat is an obligate carnivore, that would mean meat. Resources and recipes for good, homemade foods can be found in Richard Pitcairn's, "Natural Health for Dogs and Cats", "The Complete Herbal Handbook for the Dog and Cat" and "Cats Naturally" by Juliette de Bairacli Levy and "The Barf Diet" by Ian Billinghurst. Beyond diet, it is important to see if there are other factors that are contributing to your cat's constipation. Has he had bloodwork done and was it all within range? How often is Alex having a bowel movement? What do the stools look like? Colour? Consistency? Undigested food? Blood? Mucous? The answers to these questions each say something about your cat's digestion and metabolism. Other questions include: is there concurrent vomiting? What does Alex's fur look like? Does his coat and breath have an odour? Any problems with his anal glands?
You may find that the diet ideas found in these books take care of everything. If not, the questions listed would need to be answered before one could go further.