Dogs with car sickness can be relieved with medications such as chlorpheniramine maleate (Cerenia). Chlorpheniramine maleate is an antihistamine that prevents dogs from experiencing motion sickness. You need to consult your veterinarian before using it and follow the dosage of the medication as stated in the drug's instructions. Also, take care to provide your dog with plenty of water to avoid symptoms of dehydration while on the medication. If the dog still has an uncomfortable reaction when taking the drug within a few days before the trip, consider reducing the duration of the trip or having the veterinarian adjust the drug dosage and method of administration. In addition, gradual acclimatization training can be performed to allow the dog to get used to the process of traveling in the car and reduce the symptoms of motion sickness.