Sinequan (doxepin) is a tricyclic antidepressant usually prescribed to treat symptoms of depression and anxiety due to alcoholism, psychiatric conditions, or manic-depressive conditions. In some cases it may be used to treat sleep issues such as insomnia. It is also used as a second-line treatment of chronic idiopathic urticaria (dermatological itch). It comes as a white powder concentrate or a capsule.

How Does Sinequan Work?

The U.S. Food and Drug Administration (FDA) approved doxepin, the active ingredient in Sinequan, in March 1974. Sinequan acts on the norepinephrine and serotonin receptors in the axon terminals and blocks them. This medication also blocks some subtypes of serotonin, adrenergic, and histamine receptors, which causes the development of some anticholinergic and sedative effects.

On March 18, 2010, the FDA approved the New Drug Application (NDA) for doxepin for the treatment of insomnia. Although they are still prescribed in some cases, tricyclic antidepressants have largely been replaced by selective serotonin reuptake inhibitor (SSRI) antidepressants.

Chemistry of Sinequan

Sinequan is a dibenzoxepin tricyclic compound with a melting point of 25 degrees Celsius. It has a molecular formula of C19H21NO and molecular weight of 279.37614 g/mol. Sinequan has a bitter taste and is odorless. It is soluble in water and, when heated, produces toxic fumes.

Dosage FAQs

Possible Side Effects

The most prominent side effects of Sinequan include the sedative effect and the anticholinergic effects. Peripheral and central anticholinergic side effects can cause physical and mental impairment. Some of the most common include:

Precautions and Warnings Associated

Like many tricyclic antidepressants, this medication carries several important risks of which to be aware. If you are prescribed this drug, make sure your doctor and/or pharmacist addresses the following information with you:

Drug Interactions of Sinequan

Many tricyclic antidepressants have several drug interactions. Interactions for this medication include:

How to Safely Withdraw from Sinequan

Treatment with this drug should not be stopped suddenly. Withdrawal symptoms may be severe and include:

If you need to stop taking this medication, please work out a safe plan with your health care provider to slowly taper off your dosage. This will reduce the occurrence and overall severity of withdrawal symptoms.

References:

  1. Boyer, E.W. and Shannon, M. (2005). The serotonin syndrome. New England Journal of Medicine, 352, 1112–1120.
  2. Cassano, P. and Fava, M. (2004). Tolerability issues during long-term treatment with antidepressants. Annals of Clinical Psychiatry, 16, 15–25.
  3. Fava, M. (2001). Augmentation and combination strategies in treatment resistant depression. Journal of Clinical Psychiatry, 62(suppl 18), 4–11.
  4. Practice guideline for the treatment of patients with major depressive disorder (revision). (2000). American Journal of Psychiatry, 157(4 suppl), 1–45.
  5. Stahl, S.M. (2000). Essential psychopharmacology: Neuroscientific basis and practical applications. 2nd ed. New York: Cambridge University Press, 135–295.

Page content reviewed by James Pendleton, ND.