Join Date: Jun 2008
Location: northern Minnesota
Are you administering subQ fluids to your CRF cats? If not, that's something to discuss with your vet, because constipation in CRF cats is generally caused or exacerbated by dehydration. Also, stool softeners like Lactulose and Miralax only work if the cat is properly hydrated, because they hold water in the intestinal tract to soften stool as it forms.
Assuming that your cats are maintaining good hydration, you should ask your vet about Miralax or Lactulose. They are both osmotic laxatives that do a very good job of softening newly forming stool (they don't, however, soften already formed, constipated stool). I prefer Miralax because it is available OTC, and it is MUCH easier to administer than Lactulose. Miralax is a tasteless, crystalline powder that mixes easily into canned food. Lactulose, OTOH, is available by prescription only and is an extremely sticky, thick, sweet syrup that cats tend to reject.
Both are dose-to-effect drugs, meaning that you start with a low dose, then gradually adjust up or down until your cat's stool is the desired consistency. Too much will produce diarrhea. Too little will result in hard stools.