Thank you for your patience. While Levothyroixine is used in veterinary medicine to treat canine hypothyrdoidism, the dose is typically 10mcg per pound. Thus, for a normal dog with no thyroid issue, this is definitely an overdose and we could see thyroid hormone toxicosis here. Symptoms can include hyperactivity, lethargy, tachycardia, tachypnea, dyspnea, abnormal pupillary light reflexes, vomiting, and diarrhea. Jordy is right on the border of gastric emptying time, so the best way forward here to play it safe, is to get him to your local vet to induce vomiting with apomorphine. Here they can also start him on IV fluids and give activated charcoal to absorb any remainder of the drug in his GI tract. It will be important to leave him there so they can keep an eye on his heart rate and breathing if he doesn't manage to bring the tablets up.
If for some reason you can't get him seen right now, if it was definitely within the last 1.5 - 2 hours, then you could try to induce vomiting at home. There are several ways to induce vomiting, however 3% hydrogen peroxide is the most effective. As it has been about half an hour - he will likely vomit this up pretty easily. You can read about how to induce vomiting in dogs online here: http://www.petplace.com/dogs/how-to-induce-vomiting-emesis-in-dogs/page1.aspx
You would then need to keep a close eye on him, in particular on his mucus membranes, capillary refill time and respiratory rate as follows:
Mucus membranes - flip his lip and look at the color of his gums. They should maintain a nice salmon pink color. Get him to the emergency Vet if they appear white or very pale pink, or if they are a dark deep red color.
Capillary Refill time - this measures blood perfusion and test this by putting your thumb on his gum to apply pressure. After you release your thumb you will see the gum blanch. Capillary refill time is the amount of time it takes (in seconds) for the gum to return to a healthy pink color from the blanched white color. If 2 seconds or less don't worry - if it is taking significantly more time, again - off to the emergency Vet.
Respiratory Rate - if he is continuously panting throughout the night, this is a sign of shock and or pain and a signal for a trip to the emergency Vet.
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