ATC Code N05CM21, R06AA09
Formula C17H22N2O
Molar Mass (g·mol−1) 270.37
Physical State liquid
Melting Point (°C) < 25 °C
Boiling Point (°C) 139
CAS Number 469-21-6
PUB Number 3162
Drugbank ID DB00366


Doxylamine is a sedating antihistamine used to treat insomnia and allergic symptoms. In combination with pyridoxine (vitamin B6), it is also used to treat morning sickness in pregnant women. It is also used in nighttime cold medications and in pain medications containing acetaminophen and codeine to aid sleep. The drug is available over the counter and is taken perorally.

Doxylamine is a first-generation antihistamine and was first synthesized in 1948 by Nathan Sperber and colleagues in the United States.



Doxylamine acts primarily as an antagonist of the histamine H1 receptor. This action is responsible for its antihistamine and sedative properties. To a lesser extent, doxylamine acts as an antagonist of muscarinic acetylcholine receptors, an action responsible for its anticholinergic and (at high doses) deliriant effects.


Doxylamine is very rapidly absorbed enterally. It is metabolized by the liver through the enzymes CYP2D6, CYP1A2, and CYP2C9 and excreted in the urine. The half-life is about 10 hours.


Side effects

  • Dizziness
  • drowsiness
  • tiredness
  • Dry mouth
  • blurred vision
  • Constipation
  • Muscle incoordination
  • Urinary retention
  • mental confusion
  • Delirium

In rare cases, potentially life-threatening intestinal obstruction may occur.

Toxicological data

Signs of overdose include wheezing, chest tightness, fever, pruritus, severe cough, blue skin color, seizures, swelling of face, lips, tongue, or throat.

LD50, mouse, oral: 470 mg-kg-1

Markus Falkenstätter

Markus Falkenstätter

Markus Falkenstätter ist Autor zu pharmazeutischen Themen in der Medizin-Redaktion von Medikamio. Er befindet sich im letzten Semester seines Pharmaziestudiums an der Universität Wien und liebt das wissenschaftliche Arbeiten im Bereich der Naturwissenschaften.

Mag. pharm Stefanie Lehenauer

Mag. pharm Stefanie Lehenauer

Stefanie Lehenauer ist seit 2020 freie Autorin bei Medikamio und studierte Pharmazie an der Universität Wien. Sie arbeitet als Apothekerin in Wien und ihre Leidenschaft sind pflanzliche Arzneimittel und deren Wirkung.

Your personal medicine assistent

afgis-Qualitätslogo mit Ablauf Jahr/Monat: Mit einem Klick auf das Logo öffnet sich ein neues Bildschirmfenster mit Informationen über Medikamio GmbH & Co KG und sein/ihr Internet-Angebot: This website is certified by Health On the Net Foundation. Click to verify.

Search our database for drugs, sorted from A-Z with their effects and ingredients.


All substances with their common uses, chemical components and medical products which contain them.


Causes, symptoms and treatment for the most common diseases and injuries.

The contents shown do not replace the original package insert of the medicinal product, especially with regard to dosage and effect of the individual products. We cannot assume any liability for the correctness of the data, as the data was partly converted automatically. A doctor should always be consulted for diagnoses and other health questions. Further information on this topic can be found here.