Doxylamine in Unisom and Nyquil Not Recommended for Insomnia Treatment

Drug Causes Sleepiness With Potential Tolerance and Other Side Effects

In This Article

Doxylamine is found in over-the-counter products such as Unisom and Nyquil. It may be taken to treat insomnia, but is this the best treatment option for this condition? Like the related medication diphenhydramine, doxylamine does not require a prescription. What should you consider before using this medication, and what alternative sleeping pills may work better? Learn about the use of doxylamine in treating insomnia.

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


Doxylamine may be helpful for treating allergies, but a side effect is that it causes drowsiness. Some people will, therefore, take it to help with symptoms of insomnia, difficulty falling or staying asleep. It's sometimes taken to help initiate or maintain sleep, and also for nighttime relief of symptoms related to the common cold. It shouldn't be used for more than two weeks to treat insomnia.

How It Works

Doxylamine is one of the medications known as an antihistamine. Like many sleeping pills, it affects neurotransmitters: specialized chemical messengers that act within the brain and between nerve cells and other tissues. It blocks the uptake of histamine into cells, so histamine consequently builds up, leading to sleepiness. Doxylamine works centrally within the brain, where it causes sedation, and elsewhere in the body.

Who Should Not Use It

Young children under 2 years of age should not use doxylamine, nor should it be used by women who are breastfeeding, as it may pass through the milk to an infant.

There are many conditions in which you should only use doxylamine cautiously. If you have a condition that increases your eye pressure, such as glaucoma, you may need to exercise caution. Other conditions that may be problematic include:

  • 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

In addition, children under 6, and elderly patients should use caution if taking this drug.

If you're concerned about whether you may have problems using doxylamine, you should first consult with your doctor. There is also a risk for drug interactions, including with medications that affect the brain, so be sure to review your medications with your doctor 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:

  • Drowsiness
  • Dizziness
  • Loss of coordination
  • Headache
  • Stomach pain
  • Thick lung secretions
  • Dry mouth or nose
  • Hyperactivity
  • Constipation
  • Difficulty urinating
  • Low blood pressure
  • Blurred or double vision
  • Rapid or irregular heart rate
  • Sensitivity to light
  • Sweating
  • Erectile dysfunction

Potential Serious Reactions

There are also risks of serious side effects with the use of doxylamine. These effects occur more rarely:

  • Severe allergic reaction including difficulty breathing (anaphylaxis)
  • Low blood cell counts (agranulocytosis, anemia, thrombocytopenia, and leukopenia)
  • Abnormal heart rhythms
  • Seizures
  • Toxic psychosis
  • Inner ear problems (Acute labyrinthitis)

What You Should Know

Certain individuals should use doxylamine carefully or not at all, as described above. As an over-the-counter medication, the risks are thought to be slightly less compared to other prescription medications that require more careful monitoring. There are no routine tests 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.

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

Doxylamine doesn't promote sleep the way other prescribed hypnotic medications can, including benzodiazepine and non-benzodiazepine medications. It may ultimately lead to further sleep disruption, including worsened insomnia, or even dependence.

If you have any questions or concerns, you can use our Doctor Discussion Guide below to start that conversation with your doctor.

Insomnia Doctor Discussion Guide

Get our printable guide for your next doctor'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 cognitive behavioral therapy for insomnia (CBTI).

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Article Sources

  • "Doxylamine." Epocrates Rx Pro. Version 16.3, 2016. Epocrates, Inc. San Mateo, California.
  • "Doxylamine." PubMed Health. May 16, 2011.