Using a very low dose of doxepin for insomnia can benefit adults and older adults. While the medication increases sleep duration, it does not hasten sleep onset.

Insomnia is a sleep disorder in which a person has difficulty falling asleep, staying asleep, or getting a good night’s sleep. The recommended dosage of doxepin for insomnia is 3–6 milligrams (mg) per day for less than 4–8 weeks.

Although the most frequent side effects of doxepin are headache and drowsiness, the medication has the potential to cause many others.

Overdose can have serious consequences and may even be fatal.

Keep reading to learn more about the use of doxepin for insomnia, including the dosage, side effects, precautions, drug interactions, and FAQ.

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Doxepin (Silenor) is a tricyclic antidepressant, a class of medication that increases certain neurotransmitters in the brain. Neurotransmitters are chemicals that send messages among brain cells.

Doctors prescribe doxepin to treat insomnia and the following conditions:

The Food and Drug Administration (FDA) has approved doxepin for the treatment of insomnia, especially if the person has trouble with sleep maintenance.

Older research from 2014 involving 571 adults suggests that a very low dose of doxepin increases sleep duration but does not significantly affect sleep onset in adults and older adults.

What dosage is used for treating insomnia?

The dosing for insomnia is 3–6 mg daily within 30 minutes of bedtime. A person should not take doxepin for longer than 4–8 weeks.

People should follow the dosage directions carefully to avoid an overdose. They should also tell their doctor about any allergies, health conditions, and other drugs or nutritional supplements they take.

Learn more about treating insomnia.

The most frequent side effects are headaches and somnolence. Somnolence refers to a state of drowsiness or a strong desire to sleep. However, doxepin has the potential to cause side effects that fall into various categories, including those below:

Anticholinergic effects

Anticholinergic actions involve blocking the effect of a chemical called acetylcholine, which is the chief neurotransmitter of the parasympathetic nervous system (PNS). The PNS is a network of nerves that fosters calmness after stress and helps run body processes, such as digestion.

Side effects with anticholinergic actions may include:

Cardiovascular effects

The cardiovascular system refers to the heart and blood vessels. Side effects may include:

Central nervous system effects

The central nervous system (CNS) comprises the brain and spinal cord.

Drowsiness is the most common CNS side effect, but it tends to decrease with therapy. Other CNS side effects may include:

Allergic effects

These may include:

Gastrointestinal effects

The gastrointestinal system includes the stomach and other organs involved in digestion. Side effects may include:

Hematologic effects

Hematologic effects involve the blood and blood-forming organs.

Side effects may include high levels of eosinophils, a type of white blood cell that fights disease. They may also involve bone marrow depression, which results in a low number of certain types of blood cells.

Endocrine effects

The endocrine system consists of glands that secrete hormones and other substances. Side effects may include:

A person should consider the following precautions before taking doxepin:

Driving

As doxepin can cause drowsiness, a person should not drive or operate machinery before they know how the drug will affect them.

Older adults are particularly at risk of the sedating effects.

Consuming alcohol

Alcohol can increase the effects of doxepin, especially when someone consumes it in excess. An individual should ask their doctor how much alcohol is safe to consume.

Having an eye examination for glaucoma

Doxepin can cause mild dilation of the pupils, which can lead to angle-closure glaucoma in susceptible people. Angle-closure glaucoma is a condition that results in a bulging iris — the colored part of the eye — which can block the drainage of eye fluids.

A person may wish to have an eye examination to see if they are at risk of this condition. If so, undergoing a surgical procedure that removes part of the iris can help prevent it.

Some people should not take doxepin under any circumstances. These include:

  • people with certain cardiovascular conditions
  • those who are lactating or breastfeeding
  • people with a history of suicide attempts or overdose

Doxepin can interact significantly with other drugs. If a person takes a type of antidepressant called a monoamine oxidase inhibitor, such as selegiline (Zelapar), they should wait 14 days after discontinuing it before they start doxepin.

Serious side effects can also occur when someone takes doxepin with:

  • other antidepressants, such as selective serotonin reuptake inhibitors, including citalopram (Cipramil, Celexa)
  • opioids, such as oxycodone (OxyContin)
  • psychedelics, such as cannabis, otherwise called marijuana
  • herbal medications

Similar to Doxepin, trazodone is a type of antidepressant. However, where doxepin is a tricyclic antidepressant, trazodone is a serotonin antagonist and reuptake inhibitor (SARI).

Research from 2017 reports that while the benefits of taking doxepin for insomnia outweigh the risks, the risks of taking trazodone for insomnia outweigh the benefits. The authors state that doctors should not prescribe trazodone for insomnia.

Below are answers to some commonly asked questions about doxepin for insomnia:

Does diet affect its effectiveness?

Research reports that a person should not take doxepin within 3 hours after a meal. This is because taking it with food delays absorption.

What if I miss a dose?

If someone misses a dose, they should take it as soon as possible. However, if it is almost time for the next dose, they should skip the missed dose.

It is important to never take a double dose.

What to do in the event of an overdose?

A doxepin overdose can be fatal, so if a person believes they have taken too large a dose, they should go to an emergency room immediately. Symptoms of an overdose may include:

  • dilated pupils
  • confusion
  • visual hallucinations
  • vomiting
  • agitation

Life threatening symptoms of an overdose include:

  • seizures
  • abnormal heart rhythm
  • severe low blood pressure
  • coma

Research indicates that the benefits of doxepin for insomnia appear to outweigh the risks.

Despite the apparent safety, doctors do not recommend doxepin for everyone. Before taking the drug, a person should tell their doctor about any allergies or health conditions they have and other medications they take.

People should take doxepin according to directions and exercise caution in not exceeding the dosage. They should be aware that an overdose can prove dangerous.