This study is to investigate the efficacy and safety of FK199B (Zolpidem MR Tablet) by polysomnography in patients with insomnia, excluding patients with schizophrenia or manic-depressive psychosis.

Inclusion Criteria:

• Patient is diagnosed as a primary insomnia according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV)
• Patients complaining of insomnia continuously for 4 weeks or longer
• Patient's usual bedtime is between 9 p.m. and 12 a.m. for the 4 week period prior to initial screening
• Patient on most occasions sleeps for a total of ≥3 and <6.5 hours over the 4 week period prior to initial screening
• Patient's usual wake time after sleep onset in a single night is ≥45 minutes per night for the 4 week period prior to initial screening
• Patients have a body weight of ≥45 kg and ≤85 kg, a BMI of ≥18.5 and <30

Exclusion Criteria:

• Patients with schizophrenia or manic-depressive psychosis
• Patients with insomnia caused by physical diseases including chronic obstructive pulmonary disease, bronchial asthma, fibrositis syndrome, chronic fatigue syndrome, rheumatic disease, climacteric disturbance, and dermatitis atopic
• Patients with circadian rhythm sleep disorder
• Patient works night shifts
• Patients with alcoholic sleep disorder
• Patients with alcohol or drug dependence or a history of these
• Patients with insomnia related with drugs including antiparkinson, antihypertensive, or steroid drugs
• Patients with sleep apnea syndrome
• Patients with restless legs syndrome or periodic limb movement disorder
• Patients with epileptic insomnia
• Patients smoke on average 40 or more cigarettes a day
• Patients who had received psychotropic drugs other than hypnotics (including anxiolytic or antidepressant drugs for hypnotic effect) within a 4 week period prior to the initial screening