Friend, vomiting can be caused by primary problems in the gastrointestinal tract or secondary to a systemic disease. It will be difficult for me to determine the exact underlying cause without a hands on examination and some testing. But, common causes are: Dietary indiscretion, ingestion of a foreign body, infections, kidney or liver disease, pancreatitis, tumors, etc. to name a few causes. Her lack of appetite and energy are secondary to not feeling well.
In this case unfortunately we are very limited as to what you can do at home. I would strongly recommend a hands on examination by family veterinarian, xrays and blood work as initial screening test. Treatment will be based on exam and test results. In the meantime this is what you can do:
1- Do not give things like Pepto Bismol or imodium. Start her on Pepcid AC (famotidine) 10mg tablet every 12 hours. You can buy Pepcid AC over the counter in any pharmacy.
2- No food or water for 3-4 hours. Need to give her gastrointestinal tract time to rest.
3- After 3-4 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- Follow up in the morning with family veterinarian for a hands on examination.
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