An experimental drug promises to reset the body's internal clock and banish jet lag victims for good. Maryland-based Vanda Pharmaceuticals Inc. reported that its drug, tasimelteon, works by mimicking the effects of the naturally occurring hormone melatonin, which has long been identified as the regulator of the body's sleep and wake patterns.

Jet lag is a physiological condition which is a consequence of alterations to circadian rhythms. It results from rapid trans-meridian travel, as on a jet plane.

Dr. Daniel Cardinali from the University of Buenos Aires said the findings would be welcomed by millions of people - "shift-workers, airline crew, tourists, football teams, and many others." The researchers observed 450 people who went to bed five hours earlier than normal to replicate crossing into a different time zone. They found that those who took the drug enjoyed between 30 minutes and nearly two hours more sleep than volunteers who received a dummy pill.

Natural melatonin - the darkness hormone which peaks at night - is a popular treatment for patients with body clock-related sleep disorders. Dr. Shantha Rajaratnam of Brigham and Women's Hospital and Harvard Medical School in Boston and colleagues, working with the company, did both Phase II and Phase III trials of the drug, aiming to show it is safe and works.

It appears that melatonin products are already available over the counter in the US, the researchers pointed out in The Lancet. But they are not recommended because their potency, purity, and safety are not regulated by the US Food and Drug Administration. The findings are published in The Lancet. The studies on tasimelteon were undertaken by researchers from Brigham and Women's Hospital, Boston, USA and Monash University, Australia.