What is nausea and what causes it?
Nausea is the unpleasant feeling of needing to vomit. There is an area of the brain called the vomiting centre that controls the feeling of nausea and the need to vomit. It receives signals from other parts of the body such as the gut and the vestibular system (part of the ear that controls balance), as well as other parts of the brain such as the chemoreceptor trigger zone (CTZ). These signals stimulate the vomiting centre in the brain and this is why you feel nausea and a need to vomit.
There are many conditions that can cause nausea. Some of the more common ones include gastroenteritis (infection of the gut), migraine, pregnancy, anxiety, nausea caused by ear problems, and motion sickness (car or sea sickness). Other rare causes of nausea include tumours (growths) in the gut, and brain, as well as infections of the brain.
Some medicines, when taken in normal doses, may cause nausea – for example, strong painkillers such as codeine and morphine, antibiotics, as well as medicines used to treat cancer (chemotherapy). In addition, some medicines can cause nausea if you take too much of them – for example, digoxin (a medicine for the heart) or medicines that treat epilepsy. Nausea can also occur in some people after they have had surgery. This may be caused by the surgery itself or by the anaesthetic.
What are medicines for nausea and how do they work?
Medicines for nausea are used to prevent the feeling of nausea and vomiting. They are sometimes called antiemetics. Some of these medicines work on the gut and speed up how quickly food moves through it. Other medicines work on the brain and block signals to the vomiting centre. Listed below are some of the more commonly prescribed medicines for nausea:
- Cinnarizine, cyclizine, promethazine – these medicines belong to a group of medicines called antihistamines. The exact way that they work is not fully understood. It is thought that antihistamines block histamine 1 (H1) receptors in the area of the brain which creates nausea in response to chemicals in the body. They are thought to work well for nausea caused by ear problems, and motion sickness.
- Hyoscine – this medicine works by blocking a chemical in the brain called acetylcholine. It is a type of medicine called an antimuscarinic (or anticholinergic) and is also thought to work well for nausea caused by ear problems, and motion sickness.
- Chlorpromazine, droperidol, perphenazine, prochlorperazine, trifluoperazine – these medicines work by blocking a chemical in the brain called dopamine. They are thought to work well for nausea that is caused by some cancers, radiation, and opiate medicines such as morphine and codeine.
- Metoclopramide and domperidone – these medicines work directly on your gut. They ease the feelings of sickness by helping to empty the stomach and speed up how quickly food moves through the gut. They are thought to work well for people with gastroenteritis.
- Dexamethasone – this is a steroid medicine. It is a man-made version of a natural hormone produced by your own body. Dexamethasone has a wide range of actions on many parts of the body. The reason why it reduces nausea isn’t clear.
- Granisetron, ondansetron, and palonosetron – these medicines work by blocking a chemical called serotonin (5-HT) in the gut, and the brain. Serotonin (5-HT) has an action in the gut and the brain to cause nausea. These medicines are useful for controlling nausea and vomiting caused by chemotherapy.
- Aprepitant and fosaprepitant – these are newer medicines and work by blocking a chemical that acts on neurokinin receptors in the body to cause nausea. They are sometimes called neurokinin-1 receptor antagonists. They are usually given to people on a certain type of chemotherapy.
- Nabilone – it is still not clear how this medicine works to control nausea. It is normally prescribed for people who are having chemotherapy.
Medicines for nausea are available as tablets capsules, liquids, suppositories, and skin patches, as well as injections that can be given into the muscle or directly into the vein. Some of these medicines are also available as tablets that dissolve in the mouth against the gum. They are called buccal tablets. These medicines come in various different brand names.
When are medicines for nausea and vomiting prescribed?
Medicines to treat nausea are usually only prescribed once your doctor is sure what is causing your nausea. This is because, in a lot of cases, if you treat the condition causing your nausea, it will go away. For example, if your nausea is caused by taking too much of a particular medicine, your doctor will reduce the dose and your nausea will often go away. If the cause of your nausea is not known, your doctor can still prescribe a medicine for you, but it is much better to know what the cause is so the right medicine can be chosen.
Which medicine is usually prescribed?
The choice of medicine depends on what is causing your nausea, if you have any other medical conditions, if you are pregnant, and on possible the side-effects of the medicines. It is not possible to list all of the conditions that can cause nausea and which treatments are usually prescribed, but some examples include:
- Motion sickness – hyoscine is thought to be the most effective medicine for motion sickness. Promethazine, cyclizine, or cinnarizine also work well but they tend to have fewer side-effects than hyoscine and some people may prefer them because they make you sleepy. Some of the other medicines that are used to treat nausea, such as domperidone, metoclopramide, or ondansetron, do not work for motion sickness. See separate article called Motion (travel) sickness for more detail.
- Pregnancy – if you are pregnant, your doctor will usually prefer not to treat nausea and vomiting with medicines unless the symptoms are severe. However, if it is decided that you need treatment, generally promethazine, prochlorperazine, or metoclopramide may be prescribed. This is because they are not thought to harm the unborn baby. See separate leaflet called Sickness and vomiting of pregnancy for more detail.
- Migraine – both metoclopramide and domperidone are thought to work well for nausea caused by a migraine. See separate article called Medicines to treat migraine attacks for more detail.
- Chemotherapy – it is not unusual to take a combination of different medicines to control nausea and vomiting if you have chemotherapy. Some chemotherapy medicines are more likely than others to cause nausea and vomiting. If you have chemotherapy that has a low risk of nausea, your doctor will usually prescribe metoclopramide or domperidone. If you have chemotherapy that has a high risk of nausea, three medicines that work in a different way to each other may be prescribed – for example, ondansetron, dexamethasone, and aprepitant.
How should I take these medicines?
The way these medicines are taken depends on what is causing your nausea. For some conditions like motion sickness it is best to take these medicines a number of hours before you travel. This allows the medicine some time to work and prevent the feeling of nausea. For people who have chemotherapy, the doctor may advise you to take these medicines the day before you come to hospital for your treatment.
Sometimes, if you are very ill you may not be able to swallow tablets, capsules or liquids. In this case your doctor may decide to try another way of giving you these medicines. For example, you can have a skin patch, a suppository (medicine that is inserted into the rectum (back passage)) or a tablet that dissolves in the mouth, against the gum and upper lip. If nausea and vomiting are severe, your doctor may give you an injection.
For more information, see the leaflet that comes with your medicine.
What is the usual length of treatment?
Usually medicines to treat nausea are only taken for a short time, until the cause of the nausea has been treated, or you get better. For example, if your nausea is caused by gastroenteritis you will only need to take these medicines for a few days, until the symptoms have eased.
What about side-effects?
It is not possible to list all the possible side-effects of each of these medicines in this leaflet. However, as with all medicines, there are a number of side-effects that have been reported. If you want more information specific to your medicine, see the information leaflet that came with your medicine.
Most side-effects are not serious and each person may react differently to these medicines. Common side-effects include constipation, headaches, drowsiness, tiredness, insomnia (trouble with sleeping), and indigestion. Metoclopramide may cause muscle twitching of the shoulders, face and neck. If this happens when you are taking metoclopramide you must stop taking this medicine. Usually these symptoms go away 24 hours after stopping metoclopramide.
Who cannot take medicines for nausea?
There are very few people who cannot take a medicine for nausea. If for some reason one medicine has caused a side-effect or there is reason you cannot take one, your doctor can choose a different type of medicine that will suit you.
Can I buy medicines for nausea?
You can buy some medicines for nausea from your pharmacy. You can only buy them to treat motion sickness. Medicines that you can buy from your local pharmacy include: hyoscine (Kwells® and Joy Rides®) and cinnarizine (Stugeron®).
How to use the Yellow Card Scheme
If you think you have had a side-effect to one of your medicines, you can report this on the Yellow Card Scheme. You can report side-effects that:
- Are not discussed in the leaflet that came with your medicine.
- Cause problems that interfere with your everyday activities.
- Happen if you take more than one medicine.
You can do this online at the following web address: http://yellowcard.mhra.gov.uk
The Yellow Card Scheme is used to make pharmacists, doctors and nurses aware of any new side-effects that your medicines may have caused. If you wish to report a side-effect, you will need to provide basic information about:
- The side-effect.
- The name of the medicine which you think caused it.
- Information about the person who had the side-effect.
- Your contact details as the reporter of the side-effect.
It is helpful if you have your medication and/or the leaflet that came with it with you while you fill out the report.
References and Disclaimer | Provide feedback
- British National Formulary; 63rd Edition (Mar 2012) British Medical Association and Royal Pharmaceutical Society of Great Britain, London (link to current BNF)
- Flake AZ et al, Practical Selection of Antiemetics, American Family Physician, 2004