Article: Doxylamine

Doxylamine
Systematic (IUPAC) name
N,N-dimethyl-2- (1-phenyl-1-pyridin-2-yl-ethoxy)- ethanamine
Identifiers
CAS number	469-21-6
ATC code	R06AA09
PubChem	3162
DrugBank	APRD00937
Chemical data
Formula	C17H22N2O
Mol. weight	270.369 g/mol
Pharmacokinetic data
Bioavailability	?
Metabolism	Hepatic
Half life	10 hours
Excretion	?
Therapeutic considerations
Pregnancy cat.	A
Legal status	OTC
Routes	Oral

Doxylamine succinate is one of the many sedating antihistamines used by itself as a short-term sleep aid, in combination with other drugs as a night-time cold and allergy relief drug, and a preparation is prescribed in combination with Vitamin B6 (pyridoxine) to prevent morning sickness in pregnant women. It is marketed alone as Unisom Sleep Tabs in the United States by Pfizer, and is also one of the active ingredients in NyQuil. In Commonwealth countries, such as Australia, Canada, the UK New Zealand and South Africa, doxylamine is available prepared with paracetamol/acetaminophen and codeines under the brand name Syndol or Mersyndol, as treatment for tension headache and other types of pain, or as a general OTC sleep-aid branded as Somnil, Donormyl, DSozile and Restavit containing Doxylamine Succinate only.

It is a member of the ethanolamine class of antihistamines and has anti-allergy power far superior to virtually every other antihistamine on the market, with the exception of diphenhydramine (Benadryl®). It is also the most powerful over-the-counter sedative available in the United States, and more sedating than many prescription hypnotics. In a study, it was found to be superior to even the barbiturate, phenobarbital for use as a sedative.^{[citation needed]}

The dosage required to induce hypnosis can be as low as 6.25 mg, but is usually indicated in dosages of 12.5 mg or 25 mg. This drug should never be taken before operating heavy machinery such as an automobile. The maximum over-the-counter dosage allowed by the Food and Drug Administration (FDA) is 25mg, however, dosages up to 50mg are common in countries like Australia, where it is marketed under the names Restavit® and Dozile®.

Doxylamine succinate is a potent anticholinergic and has a side-effect profile common to such drugs (including drymouth, ataxia, urinary retention, and drowsiness).