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About Non-24


About Non-24

Non-24-Hour Sleep-Wake Disorder (Non-24) is a serious, chronic disorder that disrupts a person's circadian rhythms. Non-24 affects up to 70% of people who are totally blind, whether you were born blind or became so later in life.

Everyone has an internal circadian clock, or body clock, which runs a little longer than 24 hours. For sighted people, it is reset every day by environmental light cues. For people who are totally blind and unable to perceive light, the body clock and sleep-wake cycle can become out of sync with the 24-hour day-night cycle.

So with Non-24, you experience a constant daily shift in the times when your body expects to sleep and be awake, creating periods when you may be awake at night and want to sleep during the day.

HETLIOZ® (tasimelteon) is the first and only medication proven to treat Non-24.

There's an FDA-approved therapy that may help you sleep at night and stay awake during the day.

Ask your doctor about the first and only treatment for people who are totally blind with Non-24, called HETLIOZ® (tasimelteon). Remember to tell your healthcare provider about all of the medicines you're taking. HETLIOZ® should not be taken in combination with fluvoxamine or rifampin.

Frequently Asked Questions about Non-24.

What is Non-24?

Non-24 is a serious, chronic disorder that affects a person's circadian rhythms. It can arise at any age, and as many as 70% of people who are totally blind suffer from Non-24.

People with Non-24 who are totally blind lack the light perception necessary to synchronize the circadian clock with the 24-hour day-night cycle.

What is my internal clock/circadian clock?

The internal circadian clock is your body's natural timing mechanism. For most people, sighted or blind, it runs a little longer than 24 hours. In other words, most people's natural rhythms actually cycle a bit longer than the 24-hour day.

Because people who are sighted are able to perceive light, the brain aligns their rhythms each day with the 24-hour cycle. Light is the main environmental cue that signals the brain to reset the master body clock to the 24-hour day. But if you are totally blind and don't have light perception, you may be unable to sync your internal clock with the 24-hour day.

With Non-24, every day there's a shift—later and later—in the times when your body expects to sleep and be awake. Eventually, day becomes night and night becomes day. Your sleep-wake cycle will continue to shift. So, you will briefly line up with the 24-hour day, only to have the cycle of misalignment start all over again.

Who do I talk to if I think I, or someone I know, has Non-24?

If you think you have Non-24, talk to your doctor or other healthcare professional. If you have a friend or loved one who may have Non-24, advise them to speak with a healthcare professional.

If your doctor is not familiar with Non-24-Hour Sleep-Wake Disorder, refer him or her to

If you need help finding a doctor, HETLIOZSolutions™ may be able to help. Call 1-844-HETLIOZ. That's 1-844-438-5469, Monday through Friday, 9AM to 8PM, Eastern Standard Time. Learn more about HETLIOZSolutions.

Here's Important Safety Information for
HETLIOZ® (tasimelteon).


HETLIOZ® (HeT-lee-ōz) [tasimelteon] capsules are indicated for the treatment of:

  • Non-24-Hour Sleep-Wake Disorder (Non-24) in adults
  • Nighttime sleep disturbances in Smith-Magenis Syndrome (SMS) patients 16 years of age and older.

HETLIOZ LQ® (HeT-lee-oz el-Cue) oral suspension is indicated for:

  • Nighttime sleep disturbances in SMS in pediatric patients 3 to 15 years of age.

Important Safety Information

HETLIOZ® may cause drowsiness. After taking HETLIOZ®, limit your activity to preparing for bed. HETLIOZ® can potentially impair your ability to perform activities that require complete mental alertness.

The most common side effects associated with HETLIOZ® include headache, elevated liver enzymes (ALT), nightmares or abnormal dreams, and upper respiratory or urinary tract infection. These side effects may occur more frequently in patients 65 years of age or older. Adverse reactions were similar in patients treated for (Non-24) and patients with SMS treated for nighttime sleep disturbances. Adverse reactions were also similar in pediatric patients (3 years to 15 years) who received HETLIOZ LQ® oral suspension, and patients ≥16 years of age who received HETLIOZ® capsules.

Tell your healthcare provider about all of the medicines you're taking. HETLIOZ® should not be taken in combination with fluvoxamine or rifampin.

Tell your healthcare provider about all of your health conditions, including whether you are pregnant, are planning to become pregnant, or are breastfeeding. HETLIOZ® has not been studied in pregnant women.

The safety and effectiveness of HETLIOZ® for the treatment of Non-24-Hour in children have not been established. The safety and effectiveness of HETLIOZ LQ® oral suspension for the treatment of nighttime sleep disturbances in SMS have been established in pediatric patients 3 years and older.

HETLIOZ® is not recommended for use in patients with severe liver problems.

Consumer Important Safety Information

You are encouraged to report side effects of prescription drugs to the FDA. To report side effects, contact Vanda Pharmaceuticals Inc. at 1-844-438-5469 or or FDA at 1-800-FDA-0178 or

For more information, ask your healthcare provider or call 1-844-HETLIOZ (1-844-438-5469).

This information does not take the place of talking with your healthcare provider for medical advice about your condition or treatment.

Download an accessible PDF or listen to the full US Prescribing Information. You can also hear the full US Prescribing Information by calling 1-844-HETLIOZ (1-844-438-5469).