Night shift-workers are often advised to take a prophylactic nap prior to starting the shift in order to improve alertness and performance. However, individuals often report difficulty initiating and maintaining sleep at that time of the day secondary to the alerting influence of the near-24 hour circadian rhythm (biological clock). A sleep-promoting medication may improve the quality of an evening nap and subsequent alertness and performance during a night shift. We will use Ramelteon, a melatonin agonist that is FDA approved for insomnia, in order to test the following hypotheses:

1. ramelteon, compared with placebo, will significantly increase sleep efficiency during a 2-hour nap;
2. sleep inertia, as assessed by neurobehavioral tests and subjective and objective sleepiness assessments will not be significantly increased after ramelteon treatment compared with placebo treatment; and
3. neurobehavioral performance, subjective and objective sleepiness, and subjective mood during a simulated 8-hour night shift will be significantly improved when ramelteon is given prior to a prophylactic nap compared to a prophylactic nap with placebo.

Inclusion Criteria:

• Aged between 18-35 years;
• Non-smoking for at least 6 months;
• Healthy (no medical, psychiatric or sleep disorders);
• No clinically significant deviations from normal in medical history, vital signs, physical examination, blood chemistry and hematology, and ECG;
• Women of childbearing potential must agree to use an acceptable method of birth control, and must have a negative serum pregnancy test;
• Body mass index of > 18 or < 30 kg/m∧2;
• No drugs or medication likely to affect sleep or alertness, as determined by the investigators;
• Habitual caffeine consumption < 300 mg per day on average;
• Habitual alcohol consumption < 10 alcoholic units per week on average.

Exclusion Criteria:

• History of alcohol or substance abuse;
• Positive result on drugs of abuse screening;
• Current or past history of sleep disorders, including but not limited to obstructive sleep apnea, or any significant sleep complaint;
• Psychiatric disorder, including a history of depression or dysthymia (characterized by depressed mood on the majority of days for at least two years);
• Recent acute or chronic medical disorder, including but not limited to hepatic impairment and severe chronic obstructive pulmonary disease;
• History of intolerance or hypersensitivity to melatonin or melatonin agonists;
• Pregnancy or lactation;
• Shift work;
• Transmeridian travel (2 or more time zones) in past 2 months;
• Any other scientific or medical reason, as determined by the PI, such as non-compliance with protocol or intolerance to inpatient study conditions.

During each 28-hr inpatient study admission

Circadian phase was not measured.