From a verterinary site:
Caffeine (coffee, tea) and caffeinated items (such as energy drinks) - similar to the toxic chemical theobromide found in chocolate, caffeine can damage the heart, lungs, kidney and central nervous system. A lethal dose is considered to be around 70 mg per 1 lb body weight (150 mg / kg body weight). As an example, instant coffee contains over 60 mg caffeine per teaspoon. So, the lethal dose of caffeine for a 15 lb (6.8 kg) dog would be 17 teaspoons of instant coffee. Stronger coffees such as Turkish coffee, percolated coffees, and energy drinks would take much less to become toxic for a dog.
Symptoms: hyperactivity, excitement, restlessness, and vomiting. These can be followed by panting, weakness, rapid heart rate, drunken walking, muscle tremors and convulsions.
Possible Outcomes: Damage to heart, lungs, kidney organs, heart attack, coma or death.
Action: Take your pet to a vet immediately if you suspect a toxic dose. The vet may induce vomiting or perform gastric lavage. Activated charcoal may be administered along with aggressive supportive care with fluid therapy and medications.
Read more at
http://www.dogheirs.com/dogheirs/posts/134-toxic-foods-for-dogs-drinks-beans#uW8PfYIvLxTEJ5VH.99
