Hello & welcome, I am Dr. B, a licensed veterinarian & I would like to help you with your wee one today.
In regards ***** ***** question, this would be a double dose for a dog this size. Therefore, there is high risk of gut upset (vomiting, diarrhea, appetite loss) and even a risk of a bleeding stomach ulcer. So, we'd want to be proactive here.
Now if he had this in the past 2 hours, we'd want to induce vomiting. To do so at home, you can give your wee one 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.
If its been longer but under 8 hours, 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, to counter the stomach risks, we can also start him 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 aspirin at this dose is a major overdose and the risk of adverse signs are high if you dog got this. Therefore, the above would be our course of action to limit harm and protect his stomach. Any struggles with that or signs like those I noted (or paling gums, black stool -provided you didn't use the charcoal, belly pain) and we'd want him to his vet urgently. In this situation, just in case you do wish to see an ER vet, you can check @ http://www.vetlocator.com/ or https://www.veccs.org/facility-directory/
Please take care,
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