Comparison of Volinanserin and Lormetazepam in the Treatment of Insomnia Characterized by Sleep Maintenance Difficulties

The primary objective is to compare the potential for next-day residual effects of volinanserin 2 mg/day and lormetazepam 1 mg/day by measuring the sleepiness in the morning using the patient's sleep questionnaire during 4 weeks of treatment in patients with chronic primary insomnia and sleep maintenance difficulties. Secondary objectives are to compare the clinical safety of both products, including the potential for rebound insomnia and withdrawal symptoms after treatment discontinuation, to compare the efficacy of both products on subjective sleep parameters and to compare the effects of both products on patient's daytime functioning.