In recent years, sedating
antidepressants have been increasingly used to treat
primary insomnia. Up to now, only one open pilot study with
trimipramine and one double-blind placebo-controlled study with
doxepin have provided scientific support for this approach in treating
primary insomnia. In order to test the hypothesis that sedating
antidepressants are useful in the treatment of
primary insomnia, the effect of
trimipramine on objectively and subjectively measured parameters of sleep was investigated in a double-blind placebo- and
lormetazepam-controlled study in a sample of 55 patients with
primary insomnia attending outpatient
sleep-disorder clinics.
Trimipramine was selected since it has shown positive effects on sleep continuity with a lack of REM sleep suppression in studies on depressed patients and in one pilot study on patients with
primary insomnia.
Trimipramine at an average dose of 100 mg over a period of 4 weeks significantly enhanced sleep efficiency, but not total sleep time (which had been the primary target variable) compared to placebo as measured by polysomnography. Changes in objective sleep parameters were paralleled by changes in subjective sleep parameters.
Trimipramine did not suppress REM sleep.
Lormetazepam decreased wake time and sleep stage 3 and increased REM sleep compared to placebo. After switching
trimipramine to placebo, sleep parameters returned to baseline. There was no evidence of any rebound effect from
trimipramine. Side effects from
trimipramine were only marginal. This first double-blind placebo-controlled study with
trimipramine suggests its efficacy in the treatment of
primary insomnia. However, due to the large intra- and interindividual variance in the parameters of interest before and during treatment a larger sample size would have been necessary to strengthen the validity of our findings.