Doxylamine

Doxylamine

Clinical data
Trade names	Unisom
AHFS/Drugs.com	Monograph
MedlinePlus	a682537
Pregnancy category	AU: A US: B (No risk in non-human studies) A (Briggs)
Routes of administration	Oral
ATC code	R06AA09 (WHO)
Legal status
Legal status	AU: S3 (Pharmacist only) US: OTC
Pharmacokinetic data
Bioavailability	Oral: 24.7%, Intranasal: 70.8%
Metabolism	Hepatic (CYP3A4-meditated)
Biological half-life	6–12 hours
Excretion	Urine (60%), feces (40%)
Identifiers
IUPAC name (RS)-N,N-dimethyl-2-(1-phenyl-1-pyridin-2-yl-ethoxy)-ethanamine
CAS Number	469-21-6 Y
PubChem CID	3162
IUPHAR/BPS	7171
DrugBank	DB00366 Y
ChemSpider	3050 Y
UNII	95QB77JKPL
KEGG	D07878 Y
ChEBI	CHEBI:51380 Y
ChEMBL	CHEMBL1004 Y
ECHA InfoCard	100.006.742
Chemical and physical data
Formula	C17H22N2O
Molar mass	270.369 g/mol
3D model (Jmol)	Interactive image
SMILES O(CCN(C)C)C(c1ncccc1)(c2ccccc2)C
InChI InChI=1S/C17H22N2O/c1-17(20-14-13-19(2)3,15-9-5-4-6-10-15)16-11-7-8-12-18-16/h4-12H,13-14H2,1-3H3 Y Key:HCFDWZZGGLSKEP-UHFFFAOYSA-N Y

Doxylamine is a first-generation antihistamine. It can be used by itself as a short-term sedative and in combination with other drugs to provide night-time allergy and cold relief. Doxylamine is also used in combination with the analgesics paracetamol (acetaminophen) and codeine as an analgesic/calmative preparation, and is prescribed in combination with vitamin B₆ (pyridoxine) to prevent morning sickness in pregnant women. Its fetal safety is "A" in Briggs’ Reference Guide to Foetal and Neonatal Risk.

It is used in the combination drug Pyridoxine/doxylamine to treat nausea and vomiting of pregnancy.

As of 2004, doxylamine and diphenhydramine were the agents most commonly used to treat short term insomnia. As of 2008, antihistamines were not recommended by the American Academy of Sleep Medicine for treatment of chronic insomnia "due to the relative lack of efficacy and safety data.".

The main metabolites are N-desmethyldoxylamine, N,N-didesmethyldoxylamine, and doxylamine N-oxide.

Doxylamine succinate is a potent anticholinergic and has a side-effect profile common to such drugs, including dry mouth, ataxia, urinary retention, drowsiness, memory problems, inability to concentrate, hallucinations, psychosis, and a marked increased sensitivity to external stimuli. Like many hypnotics, it should not be combined with other antihistamines, such as cetirizine (Zyrtec) or diphenhydramine (Benadryl), as this combination can increase the risk of serious side effects. Using doxylamine over a long period of time is not recommended. However, the drug is not addictive, and withdrawal effects are unlikely to be experienced with prolonged use.