Boy, that is a good question. I am not sure although I have heard of others doing this. I am sure so meone here will have the answer. Sorry you are having trouble.
For about 2 years now I've given Sophie one 500 mg cranberry capsule with breakfast and another with dinner to keep UTI's at bay. Sophie is just under 80 lbs. I would call your Vet to ask how much you should give/day.