Q. Is there anything I can give my 5-year-old cat to make her calm and comfortable during a two-hour car ride? She gets very nervous in a car. 

A. Veterinarians often prescribe various sedatives to decrease anxiety in cats for long car or plane rides. Unfortunately, many of these sedatives can have untoward side effects. For instance, acepromazine, a common drug used for its sedative effects, can lower blood pressure. Diazepam, another commonly used drug, often wears off quickly and can be toxic to the liver in some cats. It's important that you have your cat thoroughly checked by a veterinarian before administering any prescription medication, just to be certain that your cat doesn't have any underlying health problems before using a sedative on your cat.

The most common drug that I prescribe in such circumstances is an antihistamine. In general, antihistamines are safe and they do have a sedative effect on most cats that lasts 10 to 12 hours. In addition, unlike most true sedatives, the pet does not become disoriented on antihistamines. I have found that many cats become disoriented and somewhat more anxious when sedatives start wearing off, which is clearly not the intended effect. Diphenhydramine, a common, over-the-counter antihistamine, can be used at 2.2 mg/kg (1 mg/lb) every eight hours for sedation. It would be wise, however, to check with your veterinarian before administering any medication for travel.