Friend, he is not eating because he does not feel well. The big question here is: Why is he vomiting and lethargic? Vomiting can be caused by many different medical conditions. It will be difficult for me to determine the exact underlying cause without a hands on examination and some testing. But, common causes are: A simple gastritis, dietary indiscretion, pancreatitis, ingestion of a foreign body, infections, etc. to name a few causes. I am a bit concern about the pink color, this could be blood in the vomit which can be caused by any of the above mentioned diseases especially a foreign body.
I understand you are watching Nelson for a friend. I would strongly recommend having him checked by a veterinarian for a hands on examination and xrays as initial screening test as soon as you can. Treatment will be based on exam and test results. He may also need supportive care (IV fluids, antiemetics, etc.). In the meantime, in any case of vomiting the first thing to do is give the stomach time to rest. This is what you can do:
1- Do not give things like Pepto Bismol or imodium. Start him on Zantac (ranitidine) 75mg 1/2 tablet every 12 hours. You can buy Zantac over the counter in any pharmacy (chemist).
2- No food or water for 4-6 hours. Need to give his gastrointestinal tract time to rest.
3- After 4-6 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.
4- Follow up with a veterinarian for a hands on examination as soon as you can.
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