Doxylamine
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| Routes of administration | Oral |
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| Pharmacokinetic data | |
| Metabolism | Hepatic |
| Elimination half-life | variable; 6-12 hours |
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| ECHA InfoCard | 100.006.742 |
| Chemical and physical data | |
| Formula | C17H22N2O |
| Molar mass | 270.369 g/mol g·mol−1 |
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 superior to almost every other antihistamine on the market, with the exception of diphenhydramine (Benadryl®). It is also the most effective over-the-counter sedative available in the United States, and more sedating than some prescription hypnotics. In a study, it was found that doxylamine succinate is possibly more effective than the barbiturate, phenobarbital for use as a sedative.[citation needed] For this reason, doxylamine has sometimes been used off label in a manner similar to diphenhydramine for the reduction of anxiety symptoms.
The dosage required to induce hypnosis (sleep) can be as low as 6.25 mg, but is usually effective in dosages of up to 25 mg. Higher doses are not recommended by the FDA. You should know how this drug effects you before operating heavy machinery or an automobile. Single dosage recommendations of 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). Other drugs with well known anticholinergic effects include many antipsychotic and tricyclic antidepressant drugs.
External links
- Unisom (manufacturer's website)