My dog just ate 5 chocolate chip muffins which also contains cocoa powder. We live 5 hours away from any open vet services at this time. Should...

Hello and welcome to ExperHelp.com! My name is Dr Lynn Roberts (Veterinarian) and I'm going to do everything in my power to answer your question to your full satisfaction!
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I do need to know the size of your dog.

I'm so glad he's a fairly large sized dog. The ingredient in Cocoa and chocolate that causes problems in dogs is called theobromine. It can cause a dog to vomit, have diarrhea, shake, and in severe cases seizure or death. Fortunately, the size of your dog combined with the size and count of the muffins shouldn't many problems. You might see mild diarrhea tomorrow, but there shouldn't be any severe symptoms that would require an emergency visit tonight. 

Your dog would have had to ingest a lot more than 5 small muffins to develop any severe problems. You can give him a dose of pepto bismol to help calm his gastrointestinal tract. If you have tablet form, he would take 1 tablet.