An antihistamine for nausea, vomiting and motion sickness
Dimenhydrinate
An older sedating antihistamine used to prevent and treat nausea, vomiting and motion sickness.
What is Dimenhydrinate?
Dimenhydrinate is an older, sedating antihistamine used to prevent and treat nausea, vomiting and motion (travel) sickness. It works by calming the signals from the inner ear and the brain's vomiting centre that cause these symptoms. Its main drawback is drowsiness, so you should not drive or use machinery if affected, and it adds to the effects of alcohol. It also has antimuscarinic effects, such as a dry mouth and blurred vision, and is used with caution in people with glaucoma or prostate problems.
Education and reference only. This is a plain-language guide to Dimenhydrinate — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Dimenhydrinate is an older type of antihistamine used mainly as an anti-sickness medicine. It is taken to prevent and treat nausea, vomiting and the dizziness and queasiness of motion (travel) sickness, such as in cars, on boats or on planes. It is taken by mouth. Like other older antihistamines, it tends to cause drowsiness, which is its most noticeable feature. It is a long-established medicine and is closely related to other sedating antihistamines used for sickness and allergy.
How it works
Motion sickness and some other forms of nausea come from signals sent by the balance organs in the inner ear and from the brain's vomiting centre. Dimenhydrinate, by blocking histamine and having some antimuscarinic action, calms these signals, so the feeling of nausea and the urge to vomit are reduced. Taken before a journey, it can help prevent travel sickness from starting. Because it acts on the brain, it also tends to cause drowsiness, and its antimuscarinic activity can cause effects such as a dry mouth and blurred vision.
Company & origin
Originated / developed by: Generic (long-established).
An older sedating antihistamine used in the UK to prevent and treat nausea, vomiting and motion (travel) sickness.
Practical use
How to take Dimenhydrinate
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it by mouth as directed; for travel sickness, take it before the journey starts.
- Do not drive or use machinery if it makes you feel drowsy.
- Avoid or limit alcohol, as it adds to the drowsiness.
- Tell your prescriber if you have glaucoma, prostate problems or difficulty passing urine before using it.
- Seek medical advice if nausea or vomiting is severe, persistent or comes with other worrying symptoms.
Weighing it up
Advantages & disadvantages of Dimenhydrinate
Advantages
- Helps prevent and relieve nausea, vomiting and motion (travel) sickness.
- Useful taken before a journey to stop travel sickness starting.
- A long-established, well-understood medicine.
Disadvantages
- Commonly causes drowsiness, so it is not ideal before driving or with alcohol.
- Has antimuscarinic effects such as a dry mouth, and is used with caution in glaucoma or prostate problems.
- Older people are more sensitive to its drowsy and antimuscarinic effects.
Practical use
Good to know
The main practical point about dimenhydrinate is drowsiness: it commonly makes people feel sleepy, so you should not drive or operate machinery if affected, and you should be careful with alcohol, which adds to the sedation. For travel sickness it works best taken before the journey rather than once you already feel sick. It also has antimuscarinic effects, which can cause a dry mouth, blurred vision, constipation or difficulty passing urine, so it is used with caution in people with glaucoma, an enlarged prostate or urinary problems. Older people are more sensitive to both the drowsiness and the antimuscarinic effects. If nausea or vomiting is severe, persistent or comes with other warning signs, it is best to seek medical advice rather than rely on it alone.
Who should not take it / use with caution
- People who have had a serious allergic reaction to dimenhydrinate or related antihistamines should not use it.
- It is used with caution in people with glaucoma, an enlarged prostate or difficulty passing urine.
- It is used with caution in older people, who are more sensitive to drowsiness and antimuscarinic effects.
- Care is needed with alcohol and other medicines that cause drowsiness.
Monitoring
- Checking how drowsy it makes you and whether it affects driving or daily activities.
- Watching for antimuscarinic effects, especially in older people and those with prostate or glaucoma problems.
- Reviewing whether the nausea needs further investigation if it does not settle.
Side effects
- Drowsiness or sleepiness.
- Dry mouth, blurred vision or constipation from its antimuscarinic effects.
- Dizziness or, occasionally, confusion, particularly in older people.
- Difficulty passing urine, especially in men with prostate problems.
Key interactions
- Alcohol and other sedating medicines add to its drowsiness.
- Other antimuscarinic medicines can add to effects such as dry mouth and constipation.
- It may mask the warning signs of damage from some other medicines, such as certain antibiotics affecting the ears.
Available as: Tablets taken by mouth.
Answers
Dimenhydrinate: frequently asked questions
What is dimenhydrinate used for?
It is an older antihistamine used to prevent and treat nausea, vomiting and motion (travel) sickness.
Will it make me drowsy?
Yes, it commonly causes drowsiness, so you should not drive or use machinery if affected, and you should be careful with alcohol.
When should I take it for travel sickness?
It works best taken before the journey starts, rather than waiting until you already feel sick.
Who should be careful with it?
People with glaucoma, an enlarged prostate or urinary problems, and older people, because of its antimuscarinic and drowsy effects.
When should I see a doctor instead?
If nausea or vomiting is severe, persistent or comes with other worrying symptoms, seek medical advice rather than relying on it alone.
The wider class
About Sedating antihistamine (anti-sickness)
Dimenhydrinate belongs to the sedating antihistamine (anti-sickness) class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
Browse by body system
Authoritative sources
- BNF
- NICE CKS
Building a medicines information resource?
We create evidence-led, dose-free drug and formulary references for teams.