Constipation Treatment and Prevention in Dogs (cont.)


A number of laxatives are available for treating constipation. Osmotic laxatives draw water into the intestines and liquefy the feces. Products containing lactulose, which must be prescribed by your veterinarian, are among the safest and most effective. A mild osmotic laxative effect can also be obtained by adding milk to the diet in amounts that exceed the capacity of the intestinal enzyme lactase to break down lactose into absorbable sugars-in other words, enough milk to cause diarrhea in a dog who is not constipated. The lactose molecule pulls fluid into the bowel and stimulates intestinal motility.

Stimulant laxatives increase the force of intestinal peristalsis. They are highly effective in treating constipation, but repeated use can interfere with colon function. A commonly used stimulant laxative is bisacodyl (Dulcolax). The dose for dogs is 5 mg to 20 mg per day.

These laxatives are used for treating constipation only. If they are given to dog with an obstruction, they can do serious damage. They are not the laxatives of choice for preventing constipation and should not be used every day. Consult your veterinarian before you give your dog any laxative.

Preventing Constipation

Good hydration, a nonconstipating diet, and regular exercise are the best preventives, along with adding fiber to the diet, if needed. A convenient way to provide the fiber is to feed a commercial food formulated for senior dogs. You can also obtain a high-fiber diet, such as Hill's Prescription w/d, from your veterinarian.

Another way to provide additional fiber is to add a bulk-forming laxative daily to the dog's food. Bulk laxatives soften the feces and promote more frequent elimination. Commonly used bulk laxatives are unprocessed wheat bran (1 to 5 tablespoons, 15 to 75 ml per day) and Metamucil (1 to 5 teaspoons, 5 to 25 ml per day). Plain canned pumpkin (1 tablespoon to 1/2 cup, 100 ml) depending on the size of the dog, can also help. Bulk laxatives or pumpkin can be fed indefinitely without causing problems.

Emollient laxatives containing docusate are indicated when the feces are dry and hard, but should not be used if the dog is dehydrated.

Mineral oil is a lubricant laxative that facilitates the passage of hard stool through the anal canal. However, mineral oil interferes with the absorption of fat-soluble vitamins, so daily or frequent administration may cause vitamin deficiency. Mineral oil also reacts adversely with docusate and thus should not be used in conjunction with Colace and the other emollient laxatives. Never administer mineral oil by syringe because it is tasteless and can be inhaled into the lungs.

This article is excerpted from “Dog Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.