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SILENOR

Last Updated: September 23, 2010

Manufacturer:

Somaxon Pharmaceuticals

Pharmacological Class:

H₁ receptor antagonist.

Active Ingredient(s):

Doxepin (as HCl) 3mg, 6mg; tabs.

Indication(s):

Treatment of insomnia characterized by difficulty with sleep maintenance.

Pharmacology:

Doxepin binds with high affinity to the histamine H₁ receptor where it functions as an antagonist. The sleep maintenance effects of doxepin are believed to be due to the antagonism of the H₁ receptor which depresses CNS activity.

Clinical Trials:

The efficacy of Silenor in the improvement of sleep maintenance was evaluated in six randomized, double-blind clinical trials involving 1,423 adult patients with a three-month history of chronic insomnia, or transient insomnia. Duration of the studies was up to three months. Primary efficacy measures of sleep maintenance were the objective and subjective time spent awake after sleep onset (objective Wake After Sleep Onset [WASO] and subjective WASO).

The first study, a 30-day placebo-controlled trial involving 221 adult patients with chronic insomnia, demonstrated that Silenor 3mg and 6mg were superior to placebo on objective WASO. Silenor 3mg was superior to placebo on subjective WASO at night 1 only. Silenor 6mg was superior to placebo on subjective WASO at night 1, and nominally superior at some later time points out to Day 30. Two randomized, double-blind studies of three months and four weeks duration, respectively, were conducted in 494 total elderly patients with chronic insomnia. Data from the studies respectively demonstrated Silenor 3mg to be superior to placebo on objective WASO and Silenor 6mg to be superior to placebo on subjective WASO. A randomized, single-dose study conducted in 565 adults with transient insomnia during the first night in a sleep laboratory showed Silenor 6mg to be superior to placebo on objective and subjective WASO.

Legal Classification:

Adults:

Individualize. Take within 30mins of bedtime. Do not take within 3 hours of a meal. Initially 6mg once daily. Max: 6mg/day. Elderly, hepatic impairment, tendency to urinary retention: initially 3mg once daily.

Children:

Not recommended.

Contraindication(s):

During or within 14 days of MAOIs. Untreated narrow angle glaucoma. Severe urinary retention.

Warnings/Precautions:

Evaluate for co-morbid diagnoses (eg, physical or psychiatric disorders) prior to treatment. Reevaluate if insomnia persists after 7–10 days of use. Monitor for new onset behavioral changes, worsening of depression, or suicidal thinking. Hepatic impairment. Respiratory dysfunction. Severe sleep apnea: not recommended. Poor metabolizers (those with reduced CYP2D6/2C19 activity). Reevaluate periodically. Elderly. Pregnancy (Cat.C). Nursing mothers.

Interaction(s):

Additive effects with concomitant CNS depressants, antihistamines, or alcohol (avoid); reduce dose. Potentiated by cimetidine. Possible hypoglycemia with tolazamide.

Adverse Reaction(s):

Somnolence, sedation, nausea, upper respiratory tract infection, dizziness, photosensitivity, skin rash; abnormal thinking, behavioral changes, complex behaviors, sleep-driving (discontinue if occurs), amnesia, anxiety, other neuropsychiatric symptoms.