I buy most of my pet remedies from a place called only natural pet.com - they are all natural but, I do not limit myself to their products.
By the way, for constipation, as for people, the solution is magesium citrate powder. I found a great site : http://www.thepetalternative.com
and they have a lot of info such as for constipation.
I will dilute a 1/4 tsp for my Boubou and Dimitra and give it by syringe everday to clear their constipation. It is natural and it works!!!!!!!!!