The U.S. Food and Drug Administration approved Hetlioz (tasimelteon) to treat a sleep condition that affects blind individuals, HealthDay reported.

FDA announced the first drug approved to treat the sleep disorder caused by a completely blind person's inability to regulate the body clock by recognizing light from dark. The condition is also called the non-24 hour sleep wake disorder.

People with the disorder may have difficulty falling asleep or staying asleep, and may wake up groggy or feeling as if they need more rest. They often find their sleep patterns reversed- needing to sleep during the day and to be awake at night.

"Non-24- hour sleep-wake disorder can prevent blind individuals from following the normal daily schedule that we all take for granted," Eric Bastings, M.D, deputy director of the Division of Neurology Products in the FDA's Center for Drug Evaluation and Research, said in a statement. "Hetlioz can improve the ability to sleep at night and to be active during the day."

The safety and effectiveness of Hetlioz was evaluated in a clinical study of 104 completely blind people. In the trial, the most reported side effects included headache, elevated liver enzymes, unusual dreams and infections of the upper respiratory or urinary tract. The FDA said Hetlioz can impair activities that require complete mental alertness.

Although most people who are totally blind still can perceive light well enough to prevent non-24, there may be as many as 100,000 individuals in the United States with this condition, who can't perceive enough light to establish a normal night sleep schedule. Non-24 can occur at any age.

FDA officials said the new drug should be taken at the same time every night before bedtime and activities should be limited after taking the drug.