Many dog owners use peanut butter to fill a Kong or disguise medication. Unfortunately, many types are sold containing sugar, which is sad enough – I always opt for the organic stuff – but meanwhile some brands use xylitol as a sweetener.
Xylitol is categorized as sugar alcohol. Xylitol is often fatal to dogs. According to the American Society for the Prevention of Cruelty to Animals (ASPCA) Animal Poison Control Center, the number of cases of xylitol toxicosis in dogs has significantly increased since the first reports in 2002. Dogs that have eaten foods containing xylitol (greater than 100 milligrams of xylitol consumed per kilogram of bodyweight) have presented with low blood sugar (hypoglycemia), which can be life-threatening.[27] Low blood sugar can result in a loss of coordination, depression, collapse and seizures in as little as 30 minutes.[28] Intake of doses of xylitol (greater than 500 to 1000 mg/kg bodyweight) has been implicated in liver failure in dogs, which can be fatal. – Wikipedia
Clinical signs of toxication usually occur within 6–12 h of ingestion, e.g. nausea, vomiting, diarrhea, dyspnea, thirst, and increased urination. These can progress to dehydration, restlessness, hyperactivity, cardiac arrhythmias, internal bleeding, heart attacks, tachypnea, ataxia, tremors, seizures, weakness, coma, cyanosis, hypertension, hyperthermia, and eventually death.
If your dog ingests xylitol, call your veterinarian immediately.