Friend, when a dog drinks more water than usual it is a sign of an underlying medical problem. There are many possible causes. It will not be possible for me to pinpoint the exact underlying cause without a hands-on examination and some testing, I am sorry. But, common causes are an active infection, pancreatitis, hormonal disorders (diabetes, cushing's), kidney or liver disease and even cancer to name a few causes. The vomiting is secondary to what is causing him to drink excessively.
To determine which of the above is the underlying cause your family veterinarian will need to do some blood work (chemistry profile, T4 & CBC) and urinalysis as an initial screening test. Treatment will be determined by exam and test results. Strongly recommend having him checked in the morning by your veterinarian. In the meantime, this is what you can do for the vomiting:
1- Do not give things like Pepto Bismol or Imodium. Start him on Pepcid AC (famotidine) 20mg tablet every 12 hours. You can buy Pepcid AC over the counter in any pharmacy.
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, he can continue to have water but don't let him drink excessively. Leave him without food for 16-20 hours then offer a 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 with your family veterinarian for a hands on examination. If cost is a concerned I would look into your local ASPCA or Shelter where they often offer veterinary services at a lower cost.
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