Chocolate is not good for dogs, but it's not the instant death it's been made out to be either. Generally speaking, the purer the chocolate, the more dangerous it is in smaler amounts. So, white chocolate would be the least harmful and a 10 lb. dog could probably ingest as much as 20 ounces before becoming ill; milk chocolate is more harmful, then dark chocolate more than that, than the most dangerous - baking chocolate, where the same 10 lb. dog might only need to consume 2 ounces of chocolate to be sick.
Every dog is different however, just like people. We once had a German Shepherd who ate anything including a FIVE POUND solid Hershey's Kiss, without any ill effects. She even washed it down with the cardboard box it came in and the tin foil wrapping too. Didn't so much as belch, although I can only imagine the stomach ache she must have had. A Whippet is a smaller breed and is finer boned with less fat than your average German Shepherd. The purity of the chocolate and the amount ingested are what's of concern. If it was a chocolate covered eclair, I'm guessing the chocolate was somewhere between milk chocolate and dark chocolate?
What you have to watch for is heavy panting, vomiting and rapid heart beat. Vomiting may be likely anyway given that she ate who-knows-what from the garbage, but it's the strange or obviously stressed behavior that you must look for and as her owner, would be best suited to recognize in subtle changes. A day from now she'll probably be acting completely fine and you'll be out of the woods. In the mean time: watch her closely, make sure she continues her normal behaviors of eating (dog food), drinking water, and going to the bathroom. If she does begin to pant heavily and behave oddly, the ASPCA has some wonderful information on their website and they have a 24-hour emergency poison control hotline you can call. I would check out their website to see if there are any professional opinions from vets about what if anything you can give her to counteract any ill effects, and call the hotline only if you become really concerned as I'm pretty sure there's a $50 charge for an emergency consultation.
All-in-all, I'd just watch her and not be too concerned. I've seen many dogs eat chocolate and worse and be none the worse for wear.
Toxic Levels: http://www.talktothevet.com/ARTICLES/DOG…
The good news is that it takes, on average, a fairly large amount of theobromine 100-150 mg/kg to cause a toxic reaction. Although there are variables to consider like the individual sensitivity, animal size and chocolate concentration.
Milk chocolate contains 44 mg of theobromine per oz.
Semisweet chocolate contains 150mg/oz.
Baker's chocolate 390mg/oz.
Using a dose of 100 mg/kg as the toxic dose it comes out roughly as:
1 ounce per 1 pound of body weight for Milk chocolate
1 ounce per 3 pounds of body weight for Semisweet chocolate
1 ounce per 9 pounds of body weight for Baker's chocolate.
So, for example, 2 oz. of Baker's chocolate can cause great risk to an 15 lb. dog. Yet, 2 oz. of Milk chocolate usually will only cause digestive problems.
Xanthines affect the nervous system, cardiovascular system and peripheral nerves. It has a diuretic effect as well. Clinical signs:
Increased heart rate
There is no specific antidote for this poisoning. And the half life of the toxin is 17.5 hours in dogs. Induce vomiting in the first 1-2 hours if the quantity is unknown. Administering activated charcoal may inhibit absorption of the toxin. An anticonvulsant might be indicated if neurological signs are present and needs to be controlled. Oxygen therapy, intravenous medications, and fluids might be needed to protect the heart.
Milk chocolate will often cause diarrhea 12-24 hours after ingestion. This should be treated symptomatically (fluids, etc..) to prevent dehydration.