This is Dr. Christian. Welcome to JustAnswer. Grape toxicity can cause kidney failure and for a small dog this could be a toxic dose. Give your dog 2-3 teaspoons of hydrogen peroxide to cause vomiting and repeat it in 10 minutes. Typically medications are given to prevent further absorption of the grapes in the intestinal tract and fluids are given to help prevent the kidney failure. For this an emergency clinic visit is necessary. Here's a website that goes into the symptoms and problems with grapes:
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