Doxylamine in Unisom and Nyquil Not Recommended for Insomnia Treatment

Drug Causes Sleepiness With Potential Tolerance and Other Side Effects

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Doxylamine is a sleep aid found in over-the-counter products such as Unisom and Nyquil. It's sometimes taken to treat insomnia.

Like the related medication diphenhydramine, doxylamine does not require a prescription. That doesn't mean it doesn't come with potential side effects, though. Before taking doxylamine, you should learn how well it works and what problems it can cause.

Common Side Effects of Using Doxylamine for Insomnia
Verywell / Jessica Olah 


Doxylamine is an antihistamine, meaning that it treats allergies. It's also used for nighttime cold symptoms. Causing drowsiness is considered a side effect, but it can be a useful one for some people who need help getting to sleep or staying asleep. It shouldn't be used for more than two weeks to treat insomnia.

Like many sleeping pills, doxylamine affects neurotransmittersspecialized chemical messengers that send signals between brain and nerve cells (neurons). More specifically, it blocks receptors that allow the neurotransmitter histamine to affect a neuron. This causes you to get sleepy.

Doxylamine works centrally (within the central nervous system) and elsewhere in the body to sedate you.

Before Taking

As an over-the-counter medication, the risks are thought to be slightly lower than with prescription medications that require more careful monitoring. No routine tests are recommended with its use.

Ultimately, doxylamine is not the best option if you are considering taking sleeping pills; there are a number of other choices that are better suited to aiding sleep. Doxylamine doesn't promote sleep in the same way as prescription hypnotic medications, such as benzodiazepine and non-benzodiazepine medications.

To take a medication for its side effect—in this case, sleepiness—is not recommended.

Doxylamine is non-habit forming medication. However, you can develop tolerance to it and take more than needed.

Precautions and Contraindications

Doxylamine is contraindicated for various groups.

Age Restrictions

Children under 12 years of age should not use doxylamine 25 milligrams (mg). Children under 6 and elderly patients shouldn't use it without a healthcare provider's advice.


According to a National Institutes of Health publication, small, occasional doses shouldn't cause problems with breastfed babies. However, larger doses or long-term use may cause drowsiness, irritability, and colicky symptoms in babies. It may also lower your milk supply.

Medical Conditions

People with many conditions should be cautious about doxylamine as it may cause problems or drug interactions. These conditions include:

  • Glaucoma
  • Hyperthyroidism
  • Heart disease
  • High blood pressure (hypertension)
  • Asthma
  • Chronic obstructive pulmonary disease (COPD)
  • Pneumonia
  • Peptic ulcer disease
  • Prostate enlargement
  • Liver disease
  • Bowel or bladder obstruction

If you're concerned about whether you may have problems using doxylamine, you should first consult with your healthcare provider.

Negative drug interactions are also a risk, especially with other medications that affect the brain, so be sure to review your medications with your healthcare provider or pharmacist before starting to use doxylamine.

Side Effects

The list of potential side effects for any drug can be quite long, and doxylamine is no exception. Although you likely wouldn't experience most side effects, and may not have any at all, some that occur commonly with doxylamine include:

  • Dizziness
  • Loss of coordination
  • Headache
  • Stomach pain
  • Dry mouth or nose
  • Constipation
  • Difficulty urinating
  • Blurred or double vision

Potential Serious Reactions

While they're rare, serious side effects can result from the use of doxylamine, including:

  • Severe allergic reaction, including difficulty breathing (anaphylaxis)
  • Low blood cell counts (agranulocytosis, anemia, thrombocytopenia, and leukopenia)
  • Abnormal heart rhythms or altered heart rate
  • Seizures
  • Toxic psychosis
  • Inner ear problems (acute labyrinthitis)
  • Hallucinations
  • Confusion or delirium
  • Low blood pressure

Insomnia Healthcare Provider Discussion Guide

Get our printable guide for your next healthcare provider's appointment to help you ask the right questions.

Doctor Discussion Guide Man

A Word From Verywell

If you experience any difficulties when taking this drug, you should be in close contact with your primary health provider. If you wish to pursue preferred treatments for insomnia, you should likewise make an appointment and discuss the better prescription options that are available.

Effective treatment may include medications, learning better sleep habits, or cognitive behavioral therapy for insomnia (CBTI).

Frequently Asked Questions

  • Can I take Unisom every night?

    No. Unisom is intended as a temporary sleep aid and should not be taken for more than two weeks. If you need ongoing help falling asleep, speak to your healthcare provider. 

  • Does Unisom help with morning sickness?

    Yes. The doxylamine succinate in Unisom taken with vitamin B6 can treat morning sickness during pregnancy. Talk to your healthcare provider before taking the combination to be sure it’s right for you.

  • Why is doxylamine not recommended for older adults?

    Doxylamine may increase the risk for dementia. This is due to its anticholinergic properties, which means it blocks neurotransmitters that transmit messages along the nervous system. According to researchers, anticholinergics are associated with cognitive decline.

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Article Sources
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  2. Drugs and Lactation Database. Doxylamine. Bethesda, MD: National Library of Medicine (US). Updated December 3, 2018.

  3. MedlinePlus. Doxylamine. Updated February 18, 2020.

  4. Unisom. Frequently Asked Questions.

  5. Koren G, Clark S, Hankins GDV, et al. Maternal safety of the delayed-release doxylamine and pyridoxine combination for nausea and vomiting of pregnancy; a randomized placebo controlled trial. BMC Pregnancy and Childbirth. 2015;15(1):59.

  6. Coupland CAC, Hill T, Dening T, Morriss R, Moore M, Hippisley-Cox J. Anticholinergic drug exposure and the risk of dementia: a nested case-control study. JAMA Intern Med. 2019;179(8):1084. doi:10.1001/jamainternmed.2019.0677

Additional Reading
  • "Doxylamine." Epocrates Rx Pro. Version 16.3, 2016. Epocrates, Inc. San Mateo, California.