Low-dose doxepin for the treatment of insomnia: emerging data

Background: Doxepin is a tricyclic compound that has been used extensively for the treatment of depressive and anxiety disorders for approximately thirty years. It was noted early to have sedative effects and assist with the improvement of disrupted sleep patterns, but in higher antidepressant doses it was also noted to have significant anticholinergic and antinoradrenergic properties. These properties led to significant dose-limiting side effects, which at times precluded its effective use. Recently, doxepin has seen renewed interest in low doses as an H1 specific antagonist in sleep disorders. Objective: The review seeks systematically to examine currently published data on the use of doxepin for the treatment of insomnia, and its pharmacological basis. Methods: Medline articles showing from a search of 'doxepin and insomnia' were included in the review. Results/conclusion: Currently available data support the use of low-dose doxepin as preferential H1 antagonist for the treatment of primary insomnia. There are likely preferential effects upon sleep maintenance insomnia compared with sleep initiation given the role of histamine in the sleep-wake cycle.