All have slightly different characteristics, durations and side effects, said Thomas Swift, the president of American Academy of Neurology in St. Paul.
Benzodiazepines are different from older sedatives like Seconal, a barbiturate, and from anti-depressants like Zoloft and Prozac that are meant to be taken daily when used to treat panic disorders and other ongoing anxiety problems.
Some fliers said they preferred a drug like Xanax to alcohol because its effects are typically mild. It does not make them spacey or fuzzy-headed, they said. They do not stumble off a plane as if their legs are filled with putty, making it appealing to business travelers who must attend meetings after landing.
"Benzodiazepines tend to be a relatively safe drug," Swift said, adding that the main side effect in small doses is sleepiness.
The risk comes in, he said, when people borrow them from well-meaning friends.
"It's almost always a bad idea," said Swift, referring to pharmaceutical-swapping. "The doctor that prescribed the medicine for the person who had it knows the person's medical history. That's not true for person that borrowed it. There could be a contraindication to that drug."
Doctors also caution against chasing an anti-anxiety pill with a drink, because alcohol functions as a "powerful augmenter" to benzodiazepines like Xanax, said William Rickles, an assistant clinical professor in the department of psychiatry at the University of California, Los Angeles.
Unlike powerful barbiturates, the mix "doesn't drop your blood pressure and doesn't stop you breathing, so it doesn't kill you," Rickles said. "But you might sleep for a long time."
For some fliers, sleep is the goal. Neil B. Kavey, director of the Sleep Disorders Center at NewYork-Presbyterian Hospital/Columbia University Medical Center, said he has witnessed a dramatic increase in the number of patients who use these sleep drugs for flights -- most to combat jet lag, but some who simply knock themselves out to avoid anxiety -- over the last year or two.
"When I noticed the increase, I worried a bit if I would see people awakening on airplanes too heavily drugged," he said. "But I don't think I've had any incidents."