Now the main concern here will be the chocolate and cocoa in the cake mix. Both will contain theobrominine, the chocolate toxin. Since this sounds like quite a dose Buddy has had and since there is a chance he hasn't absorbed it all yet, we are best to be proactive here (especially since high dose chocolate ingestion can cause GI upset, vomiting, diarrhea, but also affect the breathing and cause seizures).
Now if we think it may have been in the last 2 hours, we can induce vomiting now. To induce vomiting at home, you can administer 3% hydrogen peroxide orally at a dose of 1ml per pound. (2 teaspoons per 10 pounds of body weight). You can give it via dropper, syringe, turkey baster – we just want to get it in. After giving this orally, move the abdomen around or get your wee one walking about to get things mixing. This should usually lead to vomiting. If it is unsuccessful after 10 minutes then it can be repeated twice more. And if we still have no vomiting, then you'd need to consider seeing your local vet (or ER vet) so that apomorphine (a very strong injectable emetic) can be administered just get this out of the stomach and avoid any adverse issues.
As well or alternatively if we are over 2 hours but under 8, you can also consider administering activated charcoal at this stage. This is available over the counter from the pharmacy (ask for the high strength version, not the one for gas) and works by binding any remaining material in the stomach. For activated charcoal, we tend to give 1-4 grams per pound every 8 hrs. This can be mixed with food to be fed or with water to syringe feed (do note that it stains, so keep it away from white carpets/clothes). This will just limit how much is absorbed and reduce the intoxication risk here.
Finally, after the above, we do want to try to address any potential GI upset here for the next 24-48 hours. To do so, you can consider offering a light diet option for a few days. Examples of an easily digestible diet include cooked white rice with boiled chicken, boiled white fish, scrambled egg, or meat baby food (as long as its free from garlic or onion powder). Ideally, we want to offer this as small frequent meals to keep the stomach settled. Further to this, we can also treat with an antacid. There are a number of antacids that are available over the counter and pet friendly. Ones we can use here include Pepcid (More Info/Dose @http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid) or Zantac (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/ranitidine-hcl-zantac). Whichever you use, we'd give this 20 minutes before food to allow absorption and of course double check with your vet before use if your wee one has any known health issues or is on any medications you haven't mentioned.
Overall, if he just had this that recently, then we may not have full absorption (which may be why his signs are mild just now). So, the above would be best to get as much of this out of his stomach as we can and bind the rest. That way we can reduce the risk for him and keep him from harm. Of course, any struggles to do so or if he has those more severe signs at any point, then we'd need a check with his vet for fluids and supportive care.
Please take care,
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