Doxylamine is a medicine that is mainly used to treat the symptoms of insomnia in the short term , as it makes sleep easier and better. It is an antihistamine drug (which blocks histamine H1 receptors).

Histamine, on the other hand, is associated with allergic symptoms. In this article we will know what doxylamine is, what are its general characteristics, indications, side effects, precautions, etc. In addition, we will also talk about insomnia.

Doxylamine: general characteristics

Doxylamine is an antihistamine drug . Specifically, it belongs to the group of antihistamines H1. Its main indication is the treatment of short-term insomnia. However, it also has other uses, such as the treatment of coughs and colds (it is usually combined with decongestants).

In its commercial format, it is usually found in envelope format (in powders that dissolve in water). We can also find it in compressed format. All this is oral.

Doxylamine, as well as other antihistamines in its group (H1), crosses the blood-brain barrier. Then, it causes drowsiness in the individual, since it inhibits the H1 receptors in charge of stimulating wakefulness. This is why it is effective in treating insomnia. Doxylamine can be bought in pharmacies, and in Spain it is not necessary to have a doctor’s prescription.

Mechanism of action

Doxylamine is an antihistamine; it is derived from ethanolamine, an organic chemical compound. Its activity is based on a competitive, reversible and non-specific antagonistic action of the histamine H1 receptors .

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Thus, doxylamine, as an antihistamine, acts by blocking the action of histamine; histamine is a substance in the body that causes allergy symptoms. Specifically, histamine is found naturally in the cells of our immune system (mainly in mast cells and basophils).

Because histamine causes the symptoms of allergy, antihistamines are prescribed to relieve its symptoms (because they block its action). Doxylamine is effective in reducing the amount of time a person spends sleeping; it also increases the depth and duration of sleep.

Pharmacokinetics

Remember that pharmacokinetics is a branch of pharmacology, responsible for studying the processes to which a drug is subjected when it is introduced and distributed throughout the body. It has to do with the metabolism of drugs, their half-life, excretion…

In the case of doxylamine, we know that its metabolism is hepatic (liver). Its half-life is 6 to 12 hours (the half-life of a drug is the amount of time it takes for it to be halved within the body). Its excretion is 60% through urine and 40% through faeces .

Mode of administration

Doxylamine is administered orally in tablet form . These should be taken 30 minutes before going to sleep. Ideally they are taken with liquid (water). Doxylamine can also be taken in sachets (powder) by pouring its contents onto the tongue.

On the other hand, as for the meals, it can be taken before or after them.

Indications

The use of doxylamine is indicated for people over 18 years old . The main indication of doxylamine is the short-term treatment of insomnia. Insomnia disorder involves a difficulty in falling asleep (baseline insomnia) and/or in maintaining sleep (maintenance insomnia).

In addition, people who have insomnia sometimes wake up early (terminal insomnia).

Other indications of doxylamine are: treatment of the common cold (helps relieve symptoms such as sneezing, runny nose and nasal congestion), as well as treatment of coughs. Doxylamine is usually taken in combination with decongestant products or drugs.

Insomnia disorder: what is it?

Since doxylamine has as its main indication the treatment of insomnia, we will see, in general, what this sleep disorder consists of, which can interfere so much in a person’s life .

The disorder of insomnia (primary insomnia), defined as such in the DSM-5 (Diagnostic Manual of Mental Disorders) implies a difficulty in initiating or maintaining sleep. It also makes it difficult to get a good night’s sleep.

Symptoms last at least 1 month. On the other hand, the sleep disturbances that such a disorder causes (or the associated daytime fatigue) lead to significant discomfort for the individual (or functional impairment).

According to the ICD-10 (International Classification of Diseases), the symptoms of primary insomnia must appear at least 3 times a week (also for at least one month, the same as the DSM-5).

This disorder is more prevalent as age increases, and it is also more prevalent in women. Primary insomnia is the most prevalent sleep-related disorder worldwide (an estimated 1-10% of the adult population suffers from it).

Precautions

Some considerations and precautions that should be known about doxylamine are should not be given to induce sleep in children; nor should it be taken with alcoholic beverages or grapefruit juice .

As we mentioned at the beginning, it should be administered from the age of 18, never in minors. It should not be administered for more than 7 days (it is a short-term pharmacological treatment).

Other aspects to know about doxylamine, is that we will have to reduce its dose (or advance its taking) in case of presenting daytime sleepiness.

Some pathologies

Also we must be careful with doxylamine in the case of epilepsy, heart failure, being an elderly person , having urinary obstruction or retention, etc.

We should be aware that this drug could worsen the symptoms of dehydration or heat stroke (this is due to the reduction in sweating caused by the anticholinergic effects of the drug).

Pregnancy and lactation

Doxylamine is contraindicated if you are pregnant. As for breastfeeding, it is not recommended, since doxylamine is likely to be excreted in breast milk and the baby may be sensitive to the effects of antihistamines. Thus, there would be risk to the baby.

Side effects

Side effects that may occur with doxylamine include the following: headache, agitation, nausea, drowsiness, dry mouth, nose and throat , nervousness and increased chest congestion.

On the other hand, there are two adverse effects of doxylamine that can be serious, and that is why it is necessary to call the emergency room if they occur; these are: vision problems and difficulty in urination.

Adverse reactions

On the other hand, adverse reactions that can originate from doxylamine are: dry mouth, drowsiness, constipation, urinary retention, vertigo, blurred vision and increased bronchial secretion.

Bibliographic references:

  • American Psychiatric Association (APA) (2014). DSM-5. Diagnostic and statistical manual of mental disorders. Madrid: Panamericana.

  • WHO (2000). ICD-10. International Classification of Diseases, Tenth Edition. Madrid. Pan-American.

  • Stahl, S.M. (2002). Essential Psychopharmacology. Neuroscientific bases and clinical applications. Barcelona: Ariel.

  • Vademecum. (2018). Doxylamine.