It takes a fair amount of chocolate to kill a pet, but chocolate can be toxic. It contains a xanthine compound called theobromine. Caffeine is another xanthine compound.
The toxic dose of theobromine is about 70 mg per pound of pet, but like many substances, it all depends on the sensitivity of the patient.
Milk chocolate contains 6 mg of theobromine per ounce. Semi-sweet chocolate contains about 22 mg/oz. and baking chocolate about 350 to 400 mg/oz.
I did have a small dog who ate a large candy bar die early on in my practice but since then I've had lot's of calls where sypmtoms were just mild GI upset, but xanthines affect the central nervous system, the cardiovascular system and peripheral nerves. Signs include hyperexitablility, hyper irritability, increased heart rate, increased urination, vomiting and muscular tremors or seizures.
Making the pet vomit is helpful if it's withing an hour or so of ingesting the chocolate and giving an absorbent like activated charcoal might help, but the main part of treatment for chocolate intoxication involves treating the symptoms: controlling seizures, heart arrthymias, intestinal spasms and diarrhea, and supportive therapy like Oxygen and IV fluids. This is a job for your vet.
Cocoa Mulch, which is sold by Home Depot, Foreman's Garden Supply and other Garden supply stores, contains a lethal ingredient called "Theobromine". It is lethal to dogs and cats. It smells like chocolate and it really attracts dogs. They will ingest this stuff and die. Several deaths already occurred in the last 2-3 weeks. Just a word of caution -- check what you are using in your gardens and be aware of what your gardeners are using in your gardens. Theobromine is the ingredient that is used to make all chocolate -- especially dark or baker's chocolate -- which is toxic to dogs. Cocoa bean shells contain potentially toxic quantities of Theobromine, a xanthine compound similar in effects to caffeine and theophylline. A dog that ingested a lethal quantity of garden mulch made from cocoa bean shells developed severe convulsions and died 17 hours later. Analysis of the stomach contents and the ingested cocoa bean shells revealed the presence of lethal amounts of Theobromine.
Article submitted by: © Roger Ross DVM