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Summary
Xylitol is a natural sugar alcohol that's commonly used as a sweetener in many consumer goods such as sugar-free gums, candies and mints, children's vitamins, mouthwash, toothpaste, baked goods and desserts. It's also available in a granulated form for baking and as a sweetener. Increasingly, it's also being used in pediatric drug formulations. Though it's been used extensively in Europe, it has only recently gained popularity in the US.
Though safe for humans to consume, even in large quantities, it's extremely toxic to dogs. In dogs, xylitol causes a strong release of insulin, the hormone responsible for allowing glucose to enter cells. If insulin concentrations are too high, blood glucose levels can drop to a dangerously low level (hypoglycemia).
Rapid onset of hypoglycemia and, later, the devastating death of liver tissue are the most common pathologies linked to xylitol intoxication in this species. Death is a common sequel to intoxication, especially if dogs do not receive rapid veterinary attention.
Though extremely toxic in dogs, it's not believed to exert similar effects in other companion animal species. However, because cats are largely unmotivated to consume sweets, it has not been thoroughly researched in this species. Owners should therefore observe caution when using xylitol-containing products.
Symptoms and Identification
Vomiting is the most common initial sign of xylitol toxicity. After that, hypoglycemiacan develop -- usually within thirty to sixty minutes after ingestion. But for some reason, hypoglycemia can be delayed in some of these patients (up to twelve hours).
The clinical signs of hypoglycemia can progress quickly from lethargy and ataxia to seizures and collapse within just a few short minutes. It's during this period that most dogs are transported to a veterinary facility for treatment. If not treated rapidly, these dogs may succumb to the effects of hypoglycemia.
Initial blood work typically reveals a profound hypoglycemia. Hyperglycemia is also a possibility in some cases, however, a fact that's typically attributed to their body's emergency response to extremely low blood sugar levels (referred to as the Somogyi effect). Other abnormalities in the lab work may include low potassium and low phosphorus levels.
Surprisingly, it seems that not all dogs will develop initial signs related to low blood sugar. Some dogs may, instead, progress to a period during which their livers will begin to fail. Dogs who have experienced the hypoglycemia after xylitol ingestion may also progress to this stage. This usually starts within twelve to twenty-four hours after exposure to xylitol. Death is likely if the toxic insult to the liver leads to its necrosis (death of liver cells).
Diagnosis is typically achieved after obtaining a history of xylitol ingestion. It's presumed, however, that many dogs have died as a result of undiagnosed xylitol intoxication. The non-specific nature of the symptoms and the lack of awareness of xylitol's presence in consumer products have doubtless conspired to confound diagnosis and therefore delay treatment.
Affected Breeds
Any breed of dog can be affected. Some breeds may be more sensitive than others but this has not yet been worked out.
Treatment
Vomiting can be induced if an animal has a history of xylitol ingestion within the past hour and is asymptomatic. A seizuring animal should never be treated with emetics!
Treatment of xylitol toxicity is generally considered supportive. There is no known antidote. Correcting low blood glucose levels and administering fluids is the mainstay of treatment early on.
All dogs should be monitored for the possibility of liver disease over a period of a few days. Those who do show signs of liver involvement should also receive supportive treatment. This may even include plasma or whole blood transfusions.
Veterinary Cost
The cost of veterinary treatment of xylitol intoxication depends on the degree to which the dog is affected and the knowledge that a dog has been exposed.
If dogs are treated soon after exposure, blood sugar levels can be reasonably maintained, and dogs never progress to a stage of liver involvement, intensive care for only a day or two may be the only expense. Even so, a minimum of $500 per day is to be expected.
If hepatic involvement ensues, dogs will typically need to be hospitalized for a period of a few days to a week in an intensive care setting. This can cost upwards of $1,000 or more a day.
Prevention
Knowing what goes into your consumer goods and keeping them away from dogs should they contain xylitol is the ideal approach in this case.
References
Lang KL. Utilization of xylitol in animals and man. In: Horecker BL, Lang K, Takagi Y. eds. International symposium on metabolism, physiology, and clinical use of pentoses and pentitols. New York: Springer-Verlag, 1969;151-157.
Kuzuya T, Kanazawa Y, Kosaka K. Stimulation of insulin secretion by xylitol in dogs. Endocrinology 1969;84:200-207.
Froesch ER, Jakob A. The metabolism of xylitol. In: Sipple HL, McNutt KW, eds. Sugars in nutrition. New York: Academic Press, 1974;241-258.
International Programme on Chemical Safety,World Health Organization.Summary of toxicological data of certain food additives: WHO food additives series no. 12: xylitol. Geneva, 1977. Available at: http://www.inchem.org/documents/jecfa/jecmono/v12je22.htm. AccessedNov 30, 2005.
Kuzuya T, Kanazawa Y, Kosaka K. Plasma insulin response to intravenously administered xylitol in dogs. Metabolism 1966;15:1149-1152.
Hirata Y, Fujisawa M, Sato H, et al. Blood glucose and plasma insulin responses to xylitol administered intravenously in dogs. Biochem Biophys Res Commun 1966;24:471-475.
Dunayer EK, Gwaltney-Brant SM. Acute hepatic failure and coagulopathyassociated with xylitol ingestion in eight dogs. J Am Vet Med Assoc 2006;229:1113-1117.
Dunayer EK. Hypoglycemia following canine ingestion of xylitol-containing gum. Vet Hum Toxicol 2004;46:87-88.
Kuzuya T, Kanazawa Y, Hayashi M, et al. Species difference in plasma insulin responses to intravenous xylitol in man and several mammals. Endocrinol Jpn 1971;18:309-320.