Treating Constipation in Cats: Medications

Constipation is a serious medical problem for cats and a distressing problem for their families. Unfortunately, it’s not rare. When you remember every cat enema you’ve ever given, constipation seems as common as two eyes.

Constipation occurs frequently in geriatric cats and in cats with arthritis, diabetes, or kidney disease. Constipation is also common in the Manx cats that inherited abnormal bone and nerves in their back ends. Cats on anti-depressants or anti-psychotic medications are also inclined to become constipated. See previous blogs for all the factors that lead to cat constipation.

We’ve been discussing methods to treat constipation (fluids, soluble and insoluble fiber, prebiotics & probiotics, Chinese herbs, laxatives, suppositories, and enemas) and now it’s time to summarize all the western medications we prescribe for constipated cats.

Cisapride (Propulsid or Prepulsid)
2.5 -5 mg/10 lb cat two or three times a day. Best if given 15 minutes before meals. (Higher doses are used by some vets.)
Cisapride increases neurotransmitter acetylcholine in the gut so that food moves more quickly through. Human pharmacies have stopped carrying Cisapride (caused arrhythmia) but special compounding pharmacies will make it up for veterinary use. Humans that developed arrhythmias were taking drugs that increased the amount of Cisapride in the body. These drugs included antibiotics, antifungal, and antiviral agents: clarithromycin, erythromycin, troleandomycin, nefazodone, fluconazole, itraconazole, ketoconazole, indinavir, and ritonavir. Cats on these drugs shouldn’t be given Cisapride.

Metoclopramide (Reglan)
.8-2.0 mg orally for 9 lb cat ½ hour before means and at bedtime.
Metoclopramide stimulates the first part of the digestive tract (stomach, and small intestine) but doesn’t change the rate that food moves through the distal portion (large intestine or colon). It is not usually as effective as Cisapride, which works in a similar fashion but does stimulate the distal colon.

Docusate (Surfak, DSS, Colace)
Docusate calcium (Surfak), Docusate sodium (DSS, Colace)
50 mg/ cat once or twice a day orally
Docusate medications are stool softeners that increase the water in the stool. Make sure the product you buy doesn’t have phenolphthalein, a stimulant laxative, because it can harm cats.

Lactulose
1-3 ml/9 lb cat (up to 3/4 teaspoon) orally, two-three times a day.
Lactulose is a sweet liquid. Cats hate the taste of this sugary medication, and many refuse to eat food that has lactulose mixed into it. Lactulose works as an osmotic laxative, so it stimulates activity and it pulls water into the stool.

Kristalose
¾ teaspoon twice a day with food.
Kristalose is a powdered form of Lactulose that can be mixed in canned food. Kristalose works as an osmotic laxative, just as Lactulose does, but many cats that won’t accept lactulose because of the flavor will accept Kristalose.

MiraLax (polyethylene glycol powder)
Wide dosage range 1/8-1/4 teaspoon orally twice a day with food. Some cats need a heaping tablespoon.)
MiraLax is a prescription-only laxative that doesn’t affect blood sugar or electrolyte balance.

Cyproheptadine
2-4 mg/cat orally once or twice a day. Taper off as soon as possible.
Cyproheptadine is an appetite stimulant that helps anorexic cats eat enough food to fill the gut and stimulate regular bowel movements. Cyproheptadine can cause dry mouth and sedation.

Misoprostol (Cytotec)
25 mcg/cat
Misoprostol is usually given because it helps prevent ulcers by inhibiting gastric acid secretion. Because one of the side effects is diarrhea, Misoprostol is used in constipated kitties with the goal of softening the firm stool enough that normal stools are passed. Misoprostol is approved for dogs, and used off label in cats

Amitiza
24 mcg/cat (½ to 1 capsule) orally each day as necessary
Amitiza hasn’t been approved for use in pets, but veterinarians are prescribing it because it works so well in humans to treat constipation. Amitiza works like Misoprostol does, and it helps keep the stool moist. Can be used with Cisapride because they act differently, but should be added at low dosages and monitored for adverse effects.

Ranitidine (Zantac) and Nizatidine (Axid)
Ranitidine is 4-8 mg/9 lb cat orally twice a day. Nizatidine is 10-20 mg/9 lb cat twice a day
Ranitidine and nizatidine are normally considered antacids, but they also stimulate gut muscles so help with constipation. Antiulcer medications cimetidine (Tagamet) and famotidine (Pepsid) don’t help with constipation. Can be used with cisapride.

Drugs that will be available soon
Prucalopride and tegaserod (Zelnorm) are two new drugs that will help constipated cats because they stimulate intestinal movement. They are not on the market yet.

Drugs that help constipated dogs but don’t help cats.
Although many drugs that benefit dogs are also helpful for cats, there are drugs that are either harm cats or are of no benefit. Two drugs that stimulate GI motility and have been used to treat canine constipation that are not helpful for cats are erythromycin and motilin.

Constipation in Cats, Don’t Get Fooled
We’ve covered feline constipation as though it were easy to diagnose and treat, but it is not. There are many factors that will fool a pet family and a veterinarian when trying to diagnose or treat a constipated cat.

First of all, it’s possible to misdiagnose constipation unless we take X-rays. For example, some little kittens, especially Manx kittens, can be constipated because they don’t have normal nerves and bone structure in their back end. Other little kitties can be constipated if they’re dehydrated, but often when we see a kitten that’s straining to pass stool so that it looks constipated, it actually has a coccidia infection. Without X-rays and stool smears and cultures, we’re not sure.

Adult cats can fool us too. Constipated cats often strain and don’t pass stool, but cats with severe diarrhea also strain and don’t pass any stool. Again, we may need X-rays, stool smears and cultures to be sure.

When families bring in a constipated cat, they’re usually convinced this is a simple matter to fix: toss in a rectal bomb and it’s outa there. Often, a simple enema or suppositories will do the trick, but some constipated cats are much SICKER than the family recognizes. Some cats become constipated because they have a serious underlying disorder such as diabetes, kidney failure, or cancer. If your cat is seriously ill, your veterinarian will help you get to the bottom of the matter—don’t be overwhelmed by how expensive the diagnosis and treatment can be for “simple” constipation.

Your Cat Constipation Resource
Over the past three weeks, we’ve filled the Caring for Pets blog with everything we know about constipated cats, and it’s been a s---load: predisposing factors, fluids, soluble and insoluble fibers, Chinese herbs, laxatives, suppositories, enemas, and medications. You can use the search function at the top of the page to help locate the topics you’re interested in and to see how much holistic veterinary health information is free, right at your fingertips.