Circadian phase-shifting effects of repeated ramelteon administration in healthy adults.
OBJECTIVE
To assess the ability of repeated daily oral ramelteon to facilitate re-entrainment of human circadian rhythms after an imposed phase advance of the sleep-wake cycle.


METHODS
A total of 75 healthy adult volunteers aged 18-45 years remained in a sleep laboratory for 6 days and 5 nights; a 5-h phase advance in their sleep-wake cycle was imposed under dim-light conditions. Oral ramelteon (1,2, 4, or 8 mg once daily for 4 days) or placebo was administered 30 min before bedtime. The primary endpoint was the phase of the circadian rhythm as assessed by the time at which salivary melatonin concentrations declined below 3 pg/mL after morning awakening (dim-light melatonin offset [DLMoff]).


RESULTS
After 4 days of once-daily treatment, participants receiving 1, 2, or 4 mg ramelteon exhibited statistically significant phase shifts in DLMoff of -88.0 (16.6), -80.5 (14.8), and -90.5 (15.2) minutes respectively, versus -7.1 (18.6) minutes for placebo (least-squares mean(SEM), p = 0.002, p = 0.003, p = 0.001, respectively). Change in DLMoff for the 8 mg dose of ramelteon, -27.9 (16.4) minutes, was not significantly different than that for placebo (p = 0.392).


CONCLUSIONS
Ramelteon (1, 2, or 4 mg per day) administered before bedtime significantly advanced the phase of the circadian rhythm after a 5-h phase advance in the sleep-wake cycle. These findings suggest that ramelteon has potential as a specific therapy for circadian rhythm sleep disorders.
Henry Ford Hospital, Sleep Center, 2799 West Grand Blvd., CFP-3, Detroit, MI 48202, USA. grichar1@gmail.com
Gary S
GS
Richardson
Phyllis C
PC
Zee
Sherry
S
Wang-Weigand
Laura
L
Rodriguez
Xuejun
X
Peng
D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D002940:Circadian Rhythm / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007192:Indenes / Q000009:adverse effects / Q000494:pharmacology*; D008297:Male; D008550:Melatonin / Q000097:blood; D017286:Polysomnography / Q000187:drug effects; D012890:Sleep / Q000187:drug effects*; D055815:Young Adult
D007192:Indenes; C495910:ramelteon; D008550:Melatonin