Your instincts are right about not feeding her prior to travel. She is still young, and her motion sickness may resolve with time and frequent trips. This is not a guarantee.
Pets that become ill during car travel may respond to some pharmaceuticals. Dimenhydrinate (Dramamine) is an antihistamine used primarily for motion sickness. Acepromazine Maleate has a mild tranquilizing affect and may control vomiting. Diazepam (Valium) is a muscle relaxant and may help with motion sickness. Diphenhydramine (Benadryl) is an antihistamine, sedative, antiemetic and is used for prevention of motion sickness. These are a few that may help if the Centrine doesn't.
In addition, canine seat belts, gates or crates are ideal for car travel to protect your pet in case of an accident. Go easy on the brakes and not so hard on those turns.
Chocolate can be fatal to pets, so keep that Halloween candy away from them.
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