What Is Doxepin Used For?

Doxepin is a tricyclic antidepressant (TCA) belonging to a class of psychotherapeutic agents known as dibenzoxepin tricyclic compounds. It is originally approved for the treatment of mood disorders such as anxiety and depression. In March 2010, low dose doxepin was granted US FDA approval for the treatment of insomnia characterized by sleep maintenance difficulty. This medicine may help improve your mood, increase your energy level, relieve anxiety, and help you sleep better. This guide does not contain all information about Doxepin, whether for mood disorders or insomnia. There are different formulations for each indication, so read the medication guide provided or consult your nurse, doctor, or pharmacist before taking Doxepin.

How it works

The exact mechanism of action of doxepin is still unclear. It is believed that it blocks the brain from reabsorbing a neurotransmitter called norepinephrine, one of the chemical messengers that regulate mood and behavior. Norepinephrine, being an excitatory (stimulating) neurotransmitter, is associated with alertness and energy. Serotonin, sometimes referred to as the “feel-good” chemical, is associated with positive feelings of wellbeing. Anxiety, depression, and other mood disorders are thought to be related to imbalances with these chemical messengers. Doxepin increases the levels of norepinephrine in your body, which may help improve your mood.

Silenor (low dose doxepin) is an H1 antagonist or histamine 1 blocker. H1 antagonists are typically used to relieve allergic reactions, but they also have sedative properties. Histamine regulates the sleep-wake cycle. It increases wakefulness upon release. Doxepin blocks histamine release and promote maintenance of sleep up to 8 hours a night. Doxepin (Silenor) is the only sedating antidepressant approved by the FDA for treating sleep-maintenance insomnia.

How to take Doxepin

Take a dose exactly as prescribed by your doctor. Consult a medical practitioner or pharmacist if you are not sure how to take Doxepin.

Sinequan oral capsule for mood disorders:

  • You may be given a starting dose of 75mg, which may be increased or reduced according to how your symptoms respond with the medication.
  • If your symptoms are severe, your doctor will probably prescribe a higher dose up to 300mg/day at maximum.
  • 150mg dose is only for maintenance therapy and not for initial dose.
  • You may experience the antidepressant effect of the drug within 2–3 weeks.

Silenor oral tablet for insomnia:

  • The recommended initial dose for adult patients is 6mg once a day
  • The recommended initial dose for elderly patients (≥ 65 years old) is 3mg once a day; daily dose can be increased to 6mg if necessary.

Things to know before taking Doxepin

Safety and effectiveness

In a random double-blind study, comparing the therapeutic effect and safety of doxepin and alprazolam among 126 outpatients with primary unipolar depression, both drugs were found to be equally effective, with lower incidence of side effects in the alprazolam treatment group. Doxepin has also been found to be effective among patients with chronic pain and depression. Significant improvement was reported after six weeks at a dosage of 200mg/day. Clinical experience and literature have shown that doxepin is safe and well tolerated, even in the elderly patients.

The effects of Silenor have been studied in older patients (18–64 years old) with primary insomnia, with well-tolerated effects and improvement in objective and subjective sleep maintenance. A review of randomized placebo-controlled trials concluded that low dose doxepin “had a small to medium effect size against placebo for sleep maintenance and sleep duration but not for sleep initiation at both immediate and short-term post treatment.”

Warnings and contraindications

  • This drug is not recommended for children below 12 years of age.
  • Tell your doctor if you are allergic to similar antidepressants such as amoxapine, and loxapine or any of the components of doxepin formulations.
  • You may be advised not to take doxepin if you have glaucoma, or difficulty urinating.
  • If you have taken a MAO inhibitor (isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, tranylcypromine, and others.) in the past 14 days, do not use doxepin.
  • Tell your doctor if you have sleep apnea, diabetes, or bipolar disorder.
  • Common side effects may include: nausea, vomiting, loss of appetite, drowsiness, vision changes, dry mouth, breast swelling, and changes in sex drive.

Drug interactions

  • Sleeping pills, muscle relaxers, and other medicines for anxiety and seizures
  • SSRI antidepressants (fluoxetine, sertraline, escitalopram, or fluvoxamine)
  • Antifungal drugs
  • Stomach acid-reducing drugs (cimetidine, omeprazole)
  • Drugs for diabetes