Doxylamine

1 medicine

Doxylamine is a sedating antihistamine used for short-term insomnia and allergy symptoms, and combined with vitamin B6 for nausea in pregnancy; avoid alcohol and other sedatives, since overdose is a well-documented cause of serious poisoning in young children.

Diclegis

Doxylamine, Pyridoxine

10/10mg

Diclegis is a womens health medication containing Doxylamine + Pyridoxine, available as 10/10mg tablets.

from $1.56 / tablet View

Key facts

  • Doxylamine is a first-generation (sedating) antihistamine. It blocks histamine and also has anticholinergic effects, which is why it makes you drowsy.
  • It is sold alone as a short-term sleep aid and combined with vitamin B6 (pyridoxine) to treat nausea and vomiting in pregnancy (sold as Diclegis or Diclectin).
  • It causes marked sedation: never combine it with alcohol, opioids, or other sedating medicines, and take care with driving.
  • Overdose, especially in young children, can cause seizures, hallucinations, and a dangerously fast heartbeat; seek emergency care immediately for any suspected overdose.

What doxylamine treats

Doxylamine treats short-term, occasional insomnia in adults, difficulty falling asleep for a night or two. Combined with pyridoxine, it treats nausea and vomiting of pregnancy when non-drug measures are not enough. Older combination cold and allergy products use it to dry up a runny nose and stop sneezing, though it does not treat a cold itself and does not clear congestion.

How doxylamine works

Histamine is a chemical the brain uses, among other things, to help keep you awake and alert. Doxylamine blocks histamine (H1) receptors, producing drowsiness and reducing sneezing and a runny nose. It also blocks acetylcholine, another signalling chemical, which is why it dries up secretions and can cause a dry mouth or blurred vision.

Before you take it

  • Avoid it if you have narrow-angle glaucoma, urinary retention, or severe asthma, since the anticholinergic effect can worsen these conditions.
  • Older adults are more sensitive to confusion, falls, and urinary retention from doxylamine, and should generally use lower doses or avoid it.
  • Tell your prescriber about other sedating medicines, including opioids, benzodiazepines, and other antihistamines, since the effects add up.
  • Keep it well out of the reach of children. Doxylamine-containing cough and cold products are a leading cause of accidental antihistamine poisoning in young children.

Side effects

Common effects include next-day grogginess, dry mouth, dizziness, blurred vision, and constipation.

Seek urgent medical care for:

  • Confusion, agitation, or hallucinations.
  • A racing or irregular heartbeat.
  • Difficulty breathing or swelling of the face, lips, or tongue.
  • Seizures.

Safety essentials

  • Overdose is dangerous and can be fatal in young children: doses several times the adult dose can cause seizures, arrhythmias, and coma. Store it well out of children's reach and never give adult sleep aids to a child.
  • Do not combine it with alcohol or other sedatives; the combined drowsiness increases the risk of falls and breathing problems.
  • If you are pregnant and using it for nausea, take only the dose your prescriber recommends. It is meant to be combined with pyridoxine and taken as directed, not used as a general sleep aid.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.