If your dog is a nervous traveller it may be a good idea to ask your vet for a sedative before going on a long car journey. Your vet will want to examine your dog first and may prescribe a drug which you can administer yourself (although they may have quite unpredictable effects). If you are given a sedative it should be administered about half an hour before the journey and will last for up to eight hours. Do not sedate your dog before a flight because if it is drowsy it will not be able to adjust its posture for sudden movements and can be thrown around the box on a bumpy flight. There is some evidence that sedatives can be dangerous for dogs travelling in the cargo hold.