An anti-sickness medicine for nausea and vomiting
Trimethobenzamide
An anti-sickness medicine used to relieve nausea and vomiting, used mainly outside the UK.
What is Trimethobenzamide?
Trimethobenzamide is an antiemetic, meaning an anti-sickness medicine used to relieve nausea and vomiting. It is mainly a United States product and is not commonly used in the UK, where other anti-sickness medicines are usually chosen. It can cause drowsiness, so care is needed with driving and alcohol. Less commonly it can cause movement-related (extrapyramidal) side effects, such as restlessness or unusual muscle movements. It is taken by mouth or, in some places, given by injection.
Education and reference only. This is a plain-language guide to Trimethobenzamide — 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
Trimethobenzamide is a medicine used to relieve nausea and vomiting. It is an antiemetic, a group of medicines that calm sickness. It is mainly used in the United States and is not a standard UK medicine, so in the UK other anti-sickness treatments are normally used instead. It is usually taken by mouth as a capsule, and in some countries can be given by injection. Like several anti-sickness medicines it can make you drowsy, so it is used with care alongside activities that need you to be alert.
How it works
Nausea and vomiting are triggered by signals in a part of the brain that controls the sick feeling. Trimethobenzamide is thought to act on this area to dampen the signals that cause vomiting, helping to settle nausea. Because it acts on the brain, it can also cause drowsiness, and, less commonly, it can affect the brain pathways that control movement, which is why it can occasionally cause restlessness or unusual muscle movements. It works while it is in the body, so it is taken as needed or as a short course for sickness.
Company & origin
Originated / developed by: Various manufacturers.
An anti-sickness medicine used mainly in the United States for nausea and vomiting; it is not a usual UK product.
Practical use
How to take Trimethobenzamide
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it by mouth as directed, usually as a short course to settle nausea and vomiting.
- Avoid driving or using machinery until you know whether it makes you drowsy.
- Be cautious with alcohol, as it can add to the drowsiness.
- Tell your prescriber promptly if you notice restlessness, stiffness or unusual muscle movements.
- Use it for as short a time as needed, as advised, rather than long term.
Weighing it up
Advantages & disadvantages of Trimethobenzamide
Advantages
- Can relieve nausea and vomiting.
- Available as a capsule taken by mouth, and by injection in some countries.
- A long-established anti-sickness option in the countries where it is used.
Disadvantages
- Commonly causes drowsiness, so care is needed with driving and alcohol.
- Can occasionally cause movement-related (extrapyramidal) side effects.
- Mainly a United States product, so it is not a usual UK medicine.
Practical use
Good to know
It helps to know that trimethobenzamide is mainly a United States medicine and is not a usual UK choice, so in the UK other anti-sickness medicines are normally prescribed. The most common effect to be aware of is drowsiness, so it is sensible to avoid driving or using machinery until you know how it affects you, and to be cautious with alcohol, which can add to the sleepiness. A less common but important point is that, like some other anti-sickness medicines, it can occasionally cause movement-related (extrapyramidal) effects, such as restlessness, muscle stiffness or unusual movements; these should be reported promptly. It is generally used for short periods to settle sickness rather than long term.
Who should not take it / use with caution
- People who have had a serious allergic reaction to trimethobenzamide should not take it.
- It is used with caution in children, in whom anti-sickness medicines of this kind need particular care.
- It is used with care in older people, who may be more sensitive to drowsiness and movement effects.
- Tell your prescriber about other medicines that cause drowsiness, as the effects can add up.
Monitoring
- Reviewing whether the nausea and vomiting are settling.
- Watching for drowsiness and any movement-related effects.
- Reviewing whether it is still needed, as it is meant for short-term use.
Side effects
- Drowsiness, the most common effect.
- Dizziness, headache or a feeling of being a bit off-balance.
- Less commonly, movement-related (extrapyramidal) effects such as restlessness, stiffness or unusual movements.
- Rarely, more serious reactions, which should prompt medical advice.
Key interactions
- Other medicines that cause drowsiness, such as sedatives and strong painkillers, add to the sleepiness.
- Alcohol increases the drowsiness, so it is best avoided or limited.
- Medicines that can cause movement effects may add to that risk, so tell your prescriber what you take.
Available as: Capsules taken by mouth, and a solution for injection in some countries.
Answers
Trimethobenzamide: frequently asked questions
What is trimethobenzamide used for?
It is an anti-sickness medicine used to relieve nausea and vomiting, used mainly in the United States rather than the UK.
Is it used in the UK?
It is mainly a United States product and is not a usual UK medicine; in the UK other anti-sickness medicines are normally prescribed instead.
Will it make me drowsy?
Drowsiness is the most common effect, so avoid driving or using machinery until you know how it affects you, and be cautious with alcohol.
Can it cause unusual movements?
Less commonly it can cause movement-related effects, such as restlessness, stiffness or unusual muscle movements; report these to your prescriber promptly.
How long should I take it?
It is generally used for a short time to settle sickness rather than long term; follow your prescriber's advice.
The wider class
About Antiemetic (anti-sickness medicine)
Trimethobenzamide belongs to the antiemetic (anti-sickness medicine) class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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