Constipation in Dogs: Causes and Treatments
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
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.
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
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.