Friday, April 29, 2011

Xylitol and its associated nastiness

Many of you pet owners out there have probably peripherally heard that xylitol, a sugar substitute, can be deadly to dogs. Xylitol is an interesting compound. It is a sugar alcohol that has numerous benefits. The first and most important is that it doesn't stimulate the release of insulin in humas. Thus, it is a good "sugar" for diabetics. It also has benefits in the dental world ("tooth friendly sugar").

So, why is it bad in dogs? Sounds like a safe sugar for them to consume, right? Well, as I frequently have to remind my clients, dogs and cats are not people. The metabolism of the canine body is not the same. For some reason that we don't understand well, xylitol causes massive insulin release in the dog. When this occurs, the blood sugar (glucose) drops precipitously leading to seizures, coma, and death.

Additionally, in some dogs, for reasons we REALLY don't understand, xylitol causes terrible liver damage (hepatic necrosis). As a result, these dogs go into liver failure, complete with vomiting, diarrhea, lethargy, jaundice, abdominal pain, and clotting problems (since most of your clotting factors are made in the liver). Electrolyte imbalances can also occur, as a spike in insulin can lead to low blood potassium. This is because one of insulin's functions is to "push" potassium into cells.

So, when an owner calls and tells us that the family dog has just ingested sugarless gum flavored with xylitol, we rush the pet in. Inducing vomiting is a mainstay of treating this toxicity. Interestingly enough, gum in particular can hang around in the stomach for days. I read about a case recently in which a dog ingested a massive amount of gum. The dog was in the hospital for 4 days with a blood glucose that would not stay stable without supplementation. On the fourth day, the dog suddenly vomited up a huge, huge wad of gum! It recovered soon after.

Usually, inducing vomiting is only helpful in the first 1-1.5 hours, but in this case, we do it regardless. Once that is finished, the patient's blood glucose is checked, as well as liver values and clotting times. Depending on how much was ingested, I usually recommend hospitalization for at least 24 hours to monitor blood glucose and liver enzymes.

Activated charcoal is commonly used in dogs that have ingested something toxic. It coats the stomach and prevents absorption of toxins. There is a great deal of debate as to whether this works with xylitol at all. There is no evidence that it hurts (other than it can cause extremely high blood sodium levels, so it should be used with care), so I generally administer it.

So far, I haven't seen a particularly nasty case, but I've read about and been tangentially involved with a couple of liver failures. They are very, very bad, but dogs can survive this. The liver is an amazing organ, capable of significant regeneration.

Sugars/sweeteners that are not toxic include sorbitol, sucrose, and aspartame. Still, you should probably avoid giving your dog (and cats) sugary treats. Xylitol is not known to cause the same syndrome in cats.


Holly said...

I knew xylitol could kill dogs, but I did not know WHY. Thanks, I am passing this link on to dog friends.

I am glad your family is ok also. The destruction down south is terrible.

HDsheena said...

Do you know anything about the use of xylitol in pet dental additives? for example
Is it a dosage thing?

The Homeless Parrot said...

HD: At this point, it is THOUGHT to be a dosage thing. I'm not sure that anyone really knows the answer though.

VIN states that at 0.2-0.4g/kg - hypoglycemia occurs and that at 1.6-2g/kg, hepatic necrosis occurs. There are several possible areas of exposure out there, including products that contain xylitol. One that I see frequently is gabapentin, an anti-seizure/neuropathic pain medication. It usually has to be compounded, and some pharmacies compound it with xylitol. Go figure. I haven't seen a reaction to that yet, but I guess it's always possible.

My gut feeling is that it's best to avoid these things, just to be on the safe side!

Anonymous said...

I would much rather give my dog SweetLeaf Stevia as I work for the company and know it is safe, but I would NEVER give my dog aspartame as I would NEVER ingest it myself! (I would also never give my dog xylitol, of course)

moontoad said...

Neurontin/gabapentin hasn't been compounded in a pharmacy in a long time. It may come from the manufacturer with xylitol,but it's not done in the pharmacy itself so much anymore.