Lactulose (Cephalic, Kristalose) for Dogs and Cats

Lactulose (Cephalic, Kristalose) for Dogs and Cats

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Overview of ?Lactulose for Canines and Felines

  • Lactulose, also known as Chronulac®, Cephulac®, Constilac® or Kristalose®,  is a special type of laxative used to treat constipation and to assist in the management of a disorder called hepatic encephalopathy in dogs and cats.
  • Lactulose is a sugar solution, a disaccharide, created from two separate sugars. It is synthetically derived from lactose and represents a combination of the simple sugars galactose and fructose.
  • Unlike other sugars, lactulose is not absorbed from the intestinal tract into the blood. Instead, it passes unchanged to the large intestine (the colon).
  • In the large intestine, lactulose is broken down by bacteria resulting in the production of various acids. These acids draw water into the colon, softening the stool and increasing the volume and resulting in a laxative effect.
  • The formed acids also attract ammonia, causing this by-product of protein metabolism to migrate from the blood into the colon. Once in the colon, the acids change ammonia to ammonium, which is then passed out in the feces.
  • Lactulose is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.
  • This drug is not approved for use in animals by the Food and Drug Administration but it is prescribed legally by veterinarians as an extra-label drug.

Brand Names and Other Names of Lactulose

  • This drug is registered for use in humans only.
  • Human formulations: Chronulac® (Merrill Dow), Cephulac® (Merrill Dow), Constilac® (Alra), Cholac® (Alra), Constulose® (Barre), Enulose® (Barre), Kristalose® and various generics.
  • Veterinary formulations: None

Uses of Lactulose for Dogs and Cats

  • Lactulose is most commonly used in the treatment of hepatic encephalopathy, a liver disorder that causes toxic products (like ammonia) to accumulate in the blood. Hepatic encephalopathy causes an abnormal mental state that may progress to coma.
  • This drug is also used as a laxative to treat constipation (infrequent or hard bowel movements caused by a relative lack of water in the stool).

Precautions and Side Effects

  • While generally safe and effective when prescribed by a veterinarian, lactulose can cause side effects in some animals.
  • Lactulose should not be used in animals with known hypersensitivity or allergy to the drug.
  • Lactulose may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with lactulose. Such drugs include other laxatives and certain antibiotics.
  • Lactulose should be used with caution in diabetic animals.
  • Since lactulose can cause diarrhea, caution must be used if lactulose is given to patients with salt (electrolyte) imbalances.
  • The most common adverse effects of the drug are abdominal cramping and flatulence (“gas”). This problem generally passes with time.
  • Diarrhea and dehydration may occur if excessive amounts of lactulose are given or water is withheld from the pet.
  • Lactulose can be difficult to administer to cats as the taste is offensive and administration can lead to profuse drooling.

How Lactulose Is Supplied

  • Lactulose is available in a syrup containing 666 mg per ml. A variety of container sizes are available.
  • Lactulose crystals for oral solution.

Dosing Information of Lactulose for Dogs and Cats

  • Medication should never be administered without first consulting your veterinarian.
  • For hepatic encephalopathy in dogs, lactulose is dosed at 15 to 30 ml per dog four times daily. With time, this dose can be altered to produce two to three soft stools per day.
  • For hepatic encephalopathy in cats, lactulose is dosed at 0.25 to 1 ml per cat. The frequency of dosing is based on the frequency of stool production. It is typically started at three times daily and then adjusted.
  • For treatment of constipation, 1 ml per 10 pounds of body weight (1 ml per 4.5 kg) is given three times daily. The dose is adjusted as needed.
  • The liquid product is often distasteful to cats. Many cat owners have better luck using the crystals sprinkled on the food. One gram of the lactulose crystals is equivalent to 1.5 mL of the liquid. The dose of the lactulose crystals is 1/2 to 3/4 tsp twice daily mixed with food. Doses are adjusted to maintain the stool consistency desired.
  • The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your pet feels better, the entire treatment plan should be completed to prevent relapse or prevent the development of resistance.


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