CHRONIC INSOMNIA, ASSOCIATED WITH IMPAIRMENT IN DAYTIME FUNCTIONING OR QUALITY OF LIFE, HAS A PREVALENCE OF 10-15%.1 RELATIVELY FEW epidemio-

1731 CHRONIC INSOMNIA, ASSOCIATED WITH IMPAIRMENT IN DAYTIME FUNCTIONING OR QUALITY OF LIFE, HAS A PREVALENCE OF 10-15%.1 RELATIVELY FEW epidemiologic studies are available which provide data on the proportion of patients with specific clinical subtypes of insomnia such as difficulty with sleep onset, difficulty maintaining sleep, or more than one insomnia complaint. Ohayon and Roth, in a large (N=26,400) cross-national community survey,2 reported that 55% of individuals with clinically significant levels of insomnia presented with difficulty maintaining sleep (nocturnal awakenings without accompanying sleep onset complaints). Insomnia characterized by nocturnal awakenings occurs at a higher rate in women and in older age groups.2,3,3,4 In addition to being one of the most common clinical presentations of primary insomnia, difficulty maintaining sleep is frequently precipitated by disturbance in the sleep environment (e.g., excessive ambient noise), traumatic events or life stresses, pain or discomfort, medical conditions (e.g., arthritis, nocturia, hot flashes), and circadian disruptions (e.g., shift work, travel across time zones).5 Insomnia symptoms are not, typically, a nightly occurrence even among patients who meet DSM-IV criteria.6,7 Given the unpredictability in the occurrence of insomnia presenting as difficulty maintaining sleep, clinicians who prescribe bedtime dosing with sleep medications are confronted with a therapeutic dilemma: how to achieve effective treatment while avoiding use of hypnotics on nights when medication is not required. One possible treatment strategy is the use of “as-needed” (pro re nata, PRN) dosing limited to nights when patients have difficulty falling asleep or returning to sleep following frequent and/or prolonged awakenings. Preliminary studies suggest that patients with insomnia have a 25-45% lower weekly frequency of pill taking when permitted to use PRN regimens.8,9,10 Efficacy and Safety of As-Needed, Post Bedtime Dosing with Indiplon in Insomnia Patients with Chronic Difficulty Maintaining Sleep