Efficacy and Safety of Zolpidem-MR Administered Over a Long Term Period as Needed for Insomnia (ZOLONG)

The primary objective of the study is to evaluate the hypnotic efficacy of zolpidem-MR 12.5 mg in comparison with placebo, when administered over a long-term period, on an "as needed" basis, in patients with chronic primary insomnia. Secondary objectives of the study are to evaluate the drug taking behavior over a long-term period and the clinical safety and tolerability of zolpidem-MR 12.5 mg in comparison to placebo administered over a long-term period, on an as needed basis.