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Silenor (doxepin)

Company: Somaxon Pharma
Approval Status: Approved March 2010
Treatment for: insomnia
Areas: Neurology & Nervous System

| General Information | Clinical Results | Side Effects | Mechanism of Action | Literature References | Additional Information |


General Information

Silenor (doxepin) binds with high affinity to the histamine H1 receptor where it functions as an antagonist. The exact mechanism by which doxepin exerts its sleep maintenance effect is unknown but is believed due to its antagonism of the H1 receptor.

Silenor is specifically indicated for the treatment of insomnia characterized by difficulty with sleep maintenance.

Silenor is supplied as an immediate release tablet for oral administration. The recommended dose of Silenor for adults is 6 mg once daily. The recommended starting dose of Silenor in elderly patients (>65 years old) is 3 mg once daily. The daily dose can be increased to 6 mg, if clinically indicated. Silenor should be taken within 30 minutes of bedtime.The total Silenor dose should not exceed 6 mg per day.


Clinical Results

FDA Approval
The efficacy of Silenor for improving sleep maintenance was supported by six randomized, double-blind studies in a total of 1,423 subjects, 18 to 93 years of age, with chronic or transient insomnia. Silenor was evaluated at doses of 1 mg, 3 mg, and 6 mg relative to placebo. The primary efficacy measures for assessment of sleep maintenance were the objective and subjective time spent awake after sleep onset (respectively, objective Wake After Sleep Onset [WASO] and subjective WASO).
Chronic Insomnia: Adults
A randomized, double-blind, parallel-group study was conducted in 221 adults with chronic insomnia. Silenor 3 mg and 6 mg was compared to placebo out to 30 days. Silenor 3 mg and 6 mg were superior to placebo on objective WASO. Silenor 3 mg was superior to placebo on subjective WASO at night 1 only. Silenor 6 mg was superior to placebo on subjective WASO at night 1, and nominally superior at some later time points out to Day 30.
Chronic Insomia: Elderly
Elderly subjects with chronic insomnia were assessed in two parallel-group studies. The first randomized, double-blind study assessed Silenor 1 mg and 3 mg relative to placebo for 3 months in inpatient and outpatient settings in elderly subjects (N=240) with chronic insomnia. Silenor 3 mg was superior to placebo on objective WASO. The second randomized, double-blind study assessed Silenor 6 mg relative to placebo for 4 weeks in an outpatient setting in elderly subjects (N=254) with chronic insomnia. On subjective WASO, Silenor 6 mg was superior to placebo.
Transient Insomnia
A randomized, double-blind, parallel-group, single-dose study enrolled 565 healthy adults who were experiencing transient insomnia during the first night in a sleep laboratory. Silenor 6 mg was superior to placebo on objective WASO and subjective WASO.
Withdrawal Effects
Potential withdrawal effects were assessed in a 35-day double blind study of adults with chronic insomnia who were randomized to placebo, Silenor 3 mg, or Silenor 6 mg. There was no indication of a withdrawal syndrome after discontinuation of Silenor treatment (3 mg or 6 mg), as measured by the Tyrer’s Symptom Checklist. Discontinuation-period emergent nausea and vomiting occurred in 5% of subjects treated with 6 mg Silenor, versus 0% in 3 mg and placebo subjects.
Rebound Insomnia Effects
Rebound insomnia, defined as a worsening in WASO compared with baseline following discontinuation of treatment, was assessed in a double-blind, 35-day study in adults with chronic insomnia. Silenor 3 mg and 6 mg showed no evidence of rebound insomnia.


Side Effects

Adverse events associated with the use of Silenor may include, but are not limited to, the following:

  • somnolence
  • sedation
  • nausea
  • upper respiratory tract infection


Mechanism of Action

Silenor (doxepin) binds with high affinity to the histamine H1 receptor where it functions as an antagonist. The exact mechanism by which doxepin exerts its sleep maintenance effect is unknown but is believed due to its antagonism of the H1 receptor.


Literature References

Scharf M, Rogowski R, Hull S, Cohn M, Mayleben D, Feldman N, Ereshefsky L, Lankford A, Roth T Efficacy and safety of doxepin 1 mg, 3 mg, and 6 mg in elderly patients with primary insomnia: a randomized, double-blind, placebo-controlled crossover study. The Journal of Clinical Psychiatry 2008 Oct;69(10):1557-64

Roth T, Rogowski R, Hull S, Schwartz H, Koshorek G, Corser B, Seiden D, Lankford A Efficacy and safety of doxepin 1 mg, 3 mg, and 6 mg in adults with primary insomnia. Sleep 2007 Nov 1;30(11):1555-61

Hajak G, Rodenbeck A, Voderholzer U, Riemann D, Cohrs S, Hohagen F, Berger M, Rüther E Doxepin in the treatment of primary insomnia: a placebo-controlled, double-blind, polysomnographic study. The Journal of Clinical Psychiatry 2001 Jun;62(6):453-63


Additional Information

For additional information regarding Silenor or insomnia, please visit the Silenor web page.




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Silenor Drug Information

The Silenor drug information shown above is licensed from Thomson CenterWatch. The information provided here is for general educational purposes only and does not constitute medical or pharmaceutical advice which should be sought from qualified medical and pharmaceutical advisers.





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