What's a safe car sickness medicine for my dog? Dramamine or Benadryl?

I'm sorry to hear that Cooper gets car sick - that's no fun for anyone! Hands down, the best anti-nausea medication for dogs is a prescription medication called Cerenia. Benadryl is an antihistamine that can be mildly sedating for some dogs, but it very rarely helps with vomiting and nausea from motion sickness. Children and adult Dramamine have different active ingredients. The dimenhydrinate in the adult form of Dramamine can be helpful with motion sickness in dogs, but it is generally less effective than Cerenia and has more possible side effects. Likewise, at only 10 pounds, Cooper is simply too tiny to be able to accurately split a Dramamine tablet into an appropriate dose. I would strongly recommend asking your vet about prescribing Cerenia. I hope that everything goes well!