Welcome! Thanks for asking your question. My name is***** am a licensed veterinarian and I will be assisting you today.
Friend, a single dose of 5mg Methimazole will not be life threatening to a 7 lbs dog. You may see symptoms like vomiting or lethargy otherwise he will be fine. I would keep an eye on Mini, if he vomits this is what you can do:
1- Do not give things like Pepto Bismol or imodium.
2- No food or water for 6-8 hours. Need to give his gastrointestinal tract time to rest.
3- After 6-8 hours offer a small amount of water. Wait half hour, if no vomiting, offer small amount of rice (50%) and boiled boneless chicken or ground beef (50%) 4-6 times a day. Keep on this diet for several days then wean into regular diet.
4- If he continues to vomit after doing the above he will need to be seen by your family veterinarian for a hands on examination.
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