Doxepin in the Treatment of Primary Insomnia: A Placebo-Controlled, Double-Blind, Polysomnographic Study

Background: Over recent years, the use ofantidepressants for the symptomatic treatment of insomnia hasgrown substantially, but controlled studies are still lacking.Our study is the first investigation to prove objective efficacyand tolerability of low doses of a sedating antidepressant in arandomized, double-blind, and placebo-controlled manner inpatients with primary insomnia.

Method: Forty-seven drug-free patients meetingDSM-IV criteria for primary insomnia (mean ± SD duration ofcomplaints = 11.2 ± 9.7 years) received either 25-50 mg of thetricyclic antidepressant doxepin or placebo for 4 weeks followedby 2 weeks of placebo withdrawal. Sleep was measured bypolysomnography at baseline and the first night of application,at 4 weeks of treatment and the first to third night ofwithdrawal, and after 2 weeks of withdrawal.

Results: In the doxepin-treated patients whocompleted the study (N = 20, 47.6 ± 11.3), medicationsignificantly increased sleep efficiency after acute (night 1, p<= .001) and subchronic (night 28, p <= .05) intakecompared with the patients who received placebo (N = 20, 47.4 ±16.8 years of age). Latency to sleep onset was not affected sincethe patients had normal baseline sleep latencies. Investigatorsfound doxepin to cause significantly (p <= .05) better globalimprovement at the first day of treatment. Patients rated sleepquality (p <= .001) and working ability (p <= .005) to besignificantly improved by doxepin during the whole treatmentperiod. Overall rebound in sleep parameters was not observed, butpatients with severe rebound insomnia were significantly morefrequent in the doxepin group (night 29, p <= .01; night 30, p<= .01; night 31, p <= .05). No significant groupdifferences in side effects were found, but 2 doxepin-treatedpatients dropped out of the study due to specific side effects(increased liver enzymes, leukopenia, and thrombopenia).

Conclusion: The results support theeffectiveness of low doses of doxepin to improve sleep andworking ability in chronic primary insomniacs, althoughsubjective effects were light to moderate, and in some patients,rebound insomnia and specific side effects have to be considered.