Air travelers for now may have to rely on coffee instead of a wonder drug to help them function in new time zones. Cephalon said on Monday that the Food and Drug Administration had declined to approve use of its alertness drug, Nuvigil, to treat jet lag. Had the drug been approved, it would have been the first prescription drug specifically designated for jet lag. Nuvigil is a slightly longer-lasting form of Cephalon's biggest seller, Provigil. Both drugs are approved to treat the excessive sleepiness associated with narcolepsy, sleep apnea and shift work. In a statement, Cephalon did not elaborate about why the FDA had rejected its application, other than to say that the agency had questioned the 'robustness' of the results of questionnaires that asked participants in the company's clinical trial how sleepy they felt after taking the drug. The FDA, as a policy, does not comment on applications it does not approve. Millions of Americans who take long trips suffer from jet lag, in which the body's internal clock is out of sync with the time in one's location, leading people to feel sleepy when they need to be awake, or alert when they should be sleeping. Nuvigil was not intended to shift the body's clock to its new time zone, only to allow people to stay awake. Provigil, also called modafinil, had sales of $1 billion last year, accounting for nearly half of Cephalon's revenue. Nuvigil, or armodafinil, had sales of $73.4 million in 2009 after reaching the market in June. Provigil is expected to face generic competition in 2012, so Cephalon is trying to shift as many patients as possible to the newer drug, which the company hopes will have a far longer patent life. Getting Nuvigil, but not Provigil, approved to treat jet lag was one element of that strategy. Cephalon's clinical trial involved 427 volunteers who were flown from the East Coast of the United States to France, then kept in a sleep lab for three days. As measured by electrodes placed on the scalp, those who took Nuvigil were less sleepy during the French daytime than those who got a placebo. In a more subjective test, in which participants were asked how sleepy they felt, the drug also did better than placebo, but not as convincingly. 