Doxylamine is an antihistamine used for insomnia and cold or allergy symptoms. It can cause side effects, some of which can be severe, and prolonged use may increase the risk of misuse and addiction. Always use doxylamine as recommended and store it safely.
- Doxylamine is an over-the-counter sleep aid and antihistamine that is available in various forms.
- The different forms of doxylamine may be used to treat allergy symptoms, insomnia, and pregnancy-related nausea.
- Doxylamine is safe for short-term use, but can cause increased risks with prolonged use or when used in combination with other substances.
What is doxylamine?
Doxylamine is an antihistamine medication available over the counter in various forms, which can be used to treat different conditions. Doxylamine is available as a tablet antihistamine containing only doxylamine succinate. This is available in generic form or brand-name forms such as Aldex AN and Unisom, in 25mg strengths. [1][2]
Doxylamine is also available in combination products, such as: [1][3]
- Aspirin, dextromethorphan, doxylamine, and phenylephrine (Alka-Seltzer Plus)
- Acetaminophen, dextromethorphan, and doxylamine (Coricidin, Tylenol, Vicks NyQuil, Zicam)
- Acetaminophen, doxylamine, and phenylephrine (Vicks NyQuil)
- Doxylamine and pyridoxine (Bonjesta, Diclegis)
How doxylamine works: Pharmacology and uses
Doxylamine is a first-generation antihistamine, which acts as a histamine receptor antagonist, thereby blocking the effects of histamine and reducing cold and flu symptoms and allergy symptoms. It also exerts a sedative effect, and as such, can be used for the short-term treatment of insomnia. [2]
Combination products that include acetaminophen, aspirin, or phenylephrine can also be used as sleep aids or allergy and cold symptom relief. Doxylamine and pyridoxine (vitamin B6) combination products are used to treat nausea and vomiting during pregnancy. [1][3]
Like other first-generation antihistamines, doxylamine crosses the blood-brain barrier and can impact muscarinic receptors. This can cause anticholinergic side effects, which can be harmful if doxylamine is used long-term. [2]
Dosage recommendations
The recommended dosage for insomnia is 25 mg to 50 mg to be taken in one dose around 30 minutes before bed. [2]
For allergy symptoms, it is recommended to take a dose of 12.5 mg once every four to six hours if needed, up to a maximum of 75 mg per day. [2]
For nausea during pregnancy, it is recommended to take 20 mg once per day at bedtime, which can be increased up to a maximum of 40 mg per day. [4]
Side effects and risks
Doxylamine can cause side effects. The following side effects are common and will tend to go away on their own, but if they persist or worsen, call a doctor for advice: [1][2]
- Drowsiness
- Dizziness
- Nausea
- Headache
- Nervousness
- Agitation
- Dry mouth or throat
- Impaired concentration
- Impaired coordination
- Constipation
- Dilated pupils
- ‘Hangover effect’
Anticholinergic and severe side effects
Anticholinergic side effects of doxylamine can occur and may be severe. If any of the following side effects occur, contact a doctor immediately: [1][2]
- Flushing and fever
- Hallucinations
- Delirium
- Impaired vision
- Urinary retention
The risk of adverse effects may be increased in young children, adults over the age of 65, pregnant and breastfeeding people, and people with a history of breathing problems, glaucoma, heart conditions, seizures, or an enlarged prostate. [1]
Addiction and misuse potential
Doxylamine does not have euphoric effects, but still be abused for its sedative effects or to enhance the effects of alcohol or other drugs. Doxylamine, like many other first-generation sedating antihistamines, has the potential for the development of tolerance and dependence, which can contribute to misuse and addiction. [5][6]
Doxylamine is not considered an addictive drug, but it is recommended not to use doxylamine for longer than two weeks. If use continues beyond this, over time, the effects of the medication reduce as the body develops a tolerance. This can lead to the use of increasing dose amounts and frequency to achieve the same effects.
It is also not uncommon for people to misuse antihistamines, such as doxylamine, for their sedating effects or to enhance the effects of other substances. Some people with insomnia may become dependent on doxylamine to sleep, and may misuse the drug to overcome their tolerance. Reports of doxylamine dependence, abuse, and addiction are limited, although there are reported cases of this. [6]
Interactions and contraindications
Other substances and medications can interact with doxylamine, which can lead to an increased risk of adverse effects and overdose, or a decrease in the effectiveness of the medication.
For example, central nervous system (CNS) depressants, such as alcohol, benzodiazepines, and opioids, should be avoided or used with caution while taking doxylamine. Combining these medications can increase risks associated with CNS depressant effects. [2]
Similarly, using two or more products for cold symptoms could cause a risk of overdose if the medications contain the same active ingredients. Also, doxylamine should not be used by someone taking a monoamine oxidase inhibitor (MAOI) antidepressant. [1][2]
Always discuss with a doctor before combining doxylamine with other substances and medications to ensure it is safe, or for advice on adjusting doses.
Safety during pregnancy and breastfeeding
Doxylamine and pyridoxine combination products have been found to be safe for use in pregnancy, with no evidence of risk to the fetus. [2]
Doxylamine succinate products can be safe to use during breastfeeding in small, infrequent doses and are not thought to cause risks to the infant. Using doxylamine in larger doses or for prolonged periods may cause some risks, such as decreased lactation and drowsiness or irritability in the infant. Children under the age of 12 are not recommended to take full doses of doxylamine. [2]
Doxylamine overdose and emergency response
Doxylamine is considered a safe medication, but there have been a few reports of people intentionally overdosing. Taking too much doxylamine can result in an overdose, which may lead to serious or life-threatening outcomes, particularly when used concurrently with other substances. Signs of doxylamine overdose can include: [2][4]
- Dry mouth
- Flushed skin
- Increased body temperature
- Impaired vision
- Urinary retention
- Delirium
- Hallucinations
- Irregular heartbeat
- Trouble breathing
- Seizures
- Rhabdomyolysis
- Loss of consciousness
If a doxylamine overdose is suspected, seek professional help immediately. If the medication was ingested recently, activated charcoal can be administered to delay absorption. Other treatments will include managing the presenting symptoms and providing close monitoring. [2]
Responsible use and when to seek medical advice
Doxylamine should be stored safely, where it cannot be accessed by children. It is important to use doxylamine as directed, never taking bigger doses or a longer duration of treatment than is recommended.
Doxylamine should not be used by anyone under the age of 12 and should be avoided or used with caution in adults over the age of 65 and people who are pregnant or breastfeeding. [2]
When to seek help
Use doxylamine exactly as instructed, to help prevent adverse effects, overdose, and addiction. It may be necessary to seek professional advice or treatment if:
- An overdose is suspected
- Serious adverse effects occur
- Symptoms are not improved with short-term doxylamine treatment
- Doxylamine is used alongside other substances, particularly CNS depressants
- There are signs of addiction or drug abuse
- The use of doxylamine, alone or with other substances, is negatively impacting well-being or functioning
Conclusion
Doxylamine can be safe when used for short-term symptom relief of allergies, insomnia, or morning sickness. Using doxylamine for prolonged periods, in higher doses than recommended, or alongside other substances can increase the risk of harm. Alternative medications are available to treat sleep issues and allergy or cold symptoms, which can be discussed with a primary care physician or pharmacist.
