If you get the real sleepin' stuff from the vet, your cat will stay fuzzy
for about hours, instead of the Xanax punch of only 3 hours.  Of course,
taking the chance that you ARE just trolling this group, I'd say you could
increase the does.  <not!>

When we traveled from FL to upstate NY, we sedated the cats (3 of them) an
hour before travel.  Once we hit the road, we took away the dry food (water
only, and only feed dry food during the entire trip).  We drove anywhere
from 6 hours (because of PoohBear's insanity) to 8 hours (a good day for
Pooh).

BTW, Xanax can kill your cat.  (But you knew that...  right-o?)

READ ALL OF THIS CARFULLY:

You should never give a drug wether presciption or over the counter to you
pet unless a vet has given directions in it's use. What works for people
usually kills cats and dogs.

http://www.psyweb.com/Drughtm/xanax.html
XANAX Generic Name: alprazolam (al PRAH zoe lam) Brand Names: Xanax, Xanax
XR. Alprazolam is an anti anxiety agent,benzodiazepine's.Used primarily for
short-term relief of mild to moderate anxiety and nervous tension.Alprazolam
is also effective in the treatment of activity depression or panic attacks.
It can be useful in treating irritable bowel syndrome and anxiety due to a
neurosis as well. Alprazolam may help the symptoms of PMS if extreme,some
cancers pains if given with various narcotics, Alprazolam is used to relieve
anxiety, nervousness, and tension associated with anxiety disorders.
agoraphobia,essential tremor,and ringing ears.

Alprazolam is in a class of drugs called benzodiazepines.
Alprazolam affects chemicals in the brain that may become unbalanced and
cause anxiety.
Alprazolam may also be used for purposes other than those listed here.

CLASS:
Triazolo Benzodiazepine's.

Generic name:
Alprazolam.

Type:
Anti anxiety.

http://www.pethealthcare.net/html/body_behavioral_drug_therapy_with_r.html
Anti-anxiety drugs:  how are they used?

For anxiety, urine marking, noise phobias, fear induced aggression,
generalized fear, waking at night, and some panic disorders, anti-anxiety
drugs such as the benzodiazepines (e.g. diazepam, alprazolam) are used.
Because of their short onset of action and relatively short duration, these
drugs are primarily used for situations that might produce temporary
anxiety, and less frequently for long term on-going problems.  Because of
potential dependency effects, gradual withdrawal is recommended after
continuous therapy.  Liver function should be monitored prior to, and during
therapy with benzodiazepines because of potential liver damage, particularly
in cats.

Benzodiazepines may cause sedation and appetite stimulation, and some pets
might even become more agitated or anxious when therapy is first initiated.
These effects usually resolve within a few days.  In some cases, as pets
become less fearful, there may be an increase in aggression, especially
between members of the same species.  Be certain to report any unexpected
behavior changes, or any medical changes such as decreased appetite or
vomiting to your veterinarian immediately.

Personally I would never give my pets any of my own medication unless I have
talked to a Veterinarian about it....

Adverse effects of Xanax in cats include: changes in behavior (irritability,
increased affection, depression, aberrant demeanor), chronic use can induce
physical dependence just like in people , overdosing can cause central
nervous system depression and as in people can cause confusion, coma,
hypotension, respiratory depression and cardiac arrest.

Xanax stays in a person's body up to 27 hours and it is not published how
long it will take to be metabolized out of your cat.

If you are concerned about your cat's behavior after being given this drug
(or in any other poison situation), call 1-800 4ANI-HELP (National Animal
Poison Control Hotline $50/call).  The Veterinary Toxicology specialists
there are awesome and will try to help you at home and if it is life
threatening will send you to your nearest vet and they will contact the vet
to give instructions to save your cats life.

Please be careful.