Doxylamine is an over-the-counter antihistamine medication, commonly used to treat allergy and cold symptoms, insomnia, and nausea in pregnancy. Doxylamine can cause mild side effects, but it is generally safe in recommended doses. High doses and prolonged use can cause serious adverse effects, which may require professional intervention.
- Doxylamine can cause side effects, which are typically mild and transient.
- Using doxylamine in higher doses than recommended or for prolonged periods can increase the risk of serious side effects, overdose, and anticholinergic toxicity.
- Always use doxylamine as instructed and seek professional support if serious side effects occur.
Common side effects of doxylamine
Doxylamine can cause side effects. Often, these are mild and will go away without the need for professional intervention. However, if they persist or worsen, contact a doctor for advice. Common side effects of doxylamine include: [1][2]
- Drowsiness
- Dizziness
- Nausea
- Headache
- Dry mouth
- Trouble concentrating
- Nervousness
- Agitation
- Impaired coordination
- Constipation
Serious adverse effects
Serious adverse effects may occur. If any of the following symptoms emerge, contact a physician immediately: [1][2]
- Flushing
- Fever
- Confusion
- Delirium
- Hallucinations
- Impaired vision
- Difficulty urinating
- Seizures
These effects are known as anticholinergic effects, which occur due to doxylamine’s impact on muscarinic acetylcholine receptors. Mild anticholinergic effects can be managed with professional support. However, these effects can become severe and may cause an increased risk of harm, particularly in older adults or those with underlying physical health issues.
Serious anticholinergic effects, including breathing difficulties, rapid heart rate, high body temperature, cognitive difficulties, or hallucinations, may be a sign of toxicity and should be treated urgently. [3]
Long-term use and safety concerns
It is advised not to use doxylamine for prolonged periods, typically up to a maximum of two weeks. Long-term use can increase the risk of: [1][4][5]
- Serious side effects
- Anticholinergic effects and toxicity
- Abuse, tolerance, and dependence
- Dementia and cognitive impairments
Overdose symptoms and emergency response
Taking more doxylamine than recommended or combining it with certain other substances may result in an overdose. Doxymaline can be lethal at doses ranging between 25 and 200mg per kg of body weight. Symptoms of doxylamine overdose include: [1][2][3]
- Extreme sedation
- Hyperthermia
- Flushed skin
- Dry mouth
- Impaired vision
- Hallucinations
- Delirium
- Increased heart rate
- Breathing difficulties
- Arrhythmia
- Seizures
- Loss of consciousness
- Rhabdomyolysis
Anticholinergic toxicity
In high doses, doxylamine can cause anticholinergic toxicity, which can cause serious or even life-threatening effects. The following mnemonic is often used to help identify anticholinergic toxicity: [3]
- Red as a beet
- Dry as a bone
- Blind as a bat
- Mad as a hatter
- Hot as a hare
- Full as a flask
In the event of a doxylamine overdose, call Poison Control (1-800-222-1222) or 911 in an emergency, such as if the individual experiences trouble breathing, seizures, or unconsciousness, as medical treatment may be necessary.
If the medication was ingested within the past hour, activated charcoal can be administered to delay absorption. Treatments can be administered to manage the presenting symptoms, and professional monitoring will be required. [3]
Doxylamine side effects in special populations
Pregnant and breastfeeding
Combination medications containing doxylamine succinate and pyridoxine hydrochloride (Diclegis) are approved to treat nausea and vomiting in pregnancy and are deemed safe for this population. [6]
Other doxylamine products are deemed safe to use as a short-term or infrequent treatment while breastfeeding. High dose or prolonged treatment can result in decreased lactation and some side effects in the infant. [2]
Elderly
Older adults over the age of 65 may be more likely to experience certain side effects of doxylamine. For example, drowsiness and unsteadiness may be more likely in this population and can increase the risk of falls or accidents. [1] Also, anticholinergic medications are linked to impaired cognition and an increased risk of dementia in this age group. [5]
Children
Children may be more susceptible to experiencing side effects than adults. Doxylamine should not be used by children under the age of 12, unless instructed by a doctor. Children under the age of 4 may be especially likely to develop adverse effects when given doxylamine. [1]
Physical health issues
Some physical health issues can increase the risk or severity of side effects, such as: [1][2]
- People with a history of urinary issues related to an enlarged prostate may be more likely to experience urinary retention with doxylamine use
- People with a history of glaucoma may be more likely to experience vision impairments
- People with a history of heart conditions or seizures may be at increased risk of side effects
Drug interactions that elevate side effect risks
Other substances, medications, and supplements could interact with doxylamine, causing an increased risk of adverse effects or a decrease in medication effectiveness. For example: [1][2]
- Other antihistamines or cough and cold medications: Using two or more medications to treat cough and cold symptoms could increase the risk of doxylamine toxicity or oversedation.
- Central nervous system (CNS) depressants: Using doxylamine with CNS depressants, such as alcohol, benzodiazepines, and opioids, can increase CNS depressant effects and the risk of oversedation and overdose.
- Monoamine oxidase inhibitors (MAOIs): MAOIs may prolong and intensify the anticholinergic and CNS effects of doxylamine, and should not be used concurrently.
Always speak with a doctor before commencing a new treatment while using another medication, to ensure it is safe to do so.
What to do if you experience side effects
Mild side effects are likely to be manageable at home, although medical advice may be helpful in some cases. If side effects persist and worsen or if serious side effects emerge, seek professional treatment. It may be necessary to alter treatment to prevent further harm. Alternative treatments are available and can be discussed with a primary care physician.
How to use doxylamine safely
To use doxylamine safely, only use it for its prescribed or recommended purpose and in the recommended dosage. Do not take higher or more frequent doses than recommended or continue treatment for longer than advised. Doxylamine is not recommended for long-term use and should not be taken regularly for more than two weeks. Prolonged or increased doxylamine use, as well as concurrent substance use, can increase the risk of adverse effects and overdose.
Children under the age of 12 should not be administered doxylamine unless specifically instructed by a physician. People who are pregnant or breastfeeding, or over the age of 65, should use doxylamine with caution and may wish to consult with a doctor before using.
When to talk to a healthcare provider
It may be necessary to speak with a healthcare provider in the following circumstances:
- If you do not notice any improvement in your symptoms after taking the medication for two weeks. Symptoms may require management with alternative treatments or could be a sign of a serious condition.
- If side effects persist or worsen, or if there are signs of serious side effects or anticholinergic effects.
- If you are taking doxylamine in larger or more frequent doses than recommended or continuing to take the medication longer than advised. Signs of misuse or addiction may require professional advice and intervention.
- If an overdose is suspected.
