Aprepitant to prevent sickness
Emend
Peer reviewed by Sid DajaniLast updated by Michael Stewart, MRPharmSLast updated 28 Dec 2022
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Aprepitant is an anti-sickness medicine. It is taken alongside other medicines to help stop sickness (nausea and vomiting) after chemotherapy.
Take one 125 mg capsule an hour before chemotherapy, and then one 80 mg capsule each morning for the following two days.
The most common side-effects are hiccups, indigestion, constipation and headache.
At a glance
Aprepitant is an anti-sickness medicine to prevent nausea and vomiting after chemotherapy.
It works by blocking a natural chemical in the body called 'substance P'.
You will take capsules over three days, starting an hour before chemotherapy.
Tell your doctor if you are pregnant, breastfeeding, or have liver problems.
Aprepitant can interfere with other medicines, including hormonal contraception.
Common side-effects include headache, tiredness, dizziness, and constipation.
In this article:
Video picks for Nausea medicine and vomiting treatment
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About aprepitant
Type of medicine | Neurokinin-receptor antagonist anti-sickness medicine |
Used for | Prevention of sickness (nausea and vomiting) associated with chemotherapy |
Also called | Emend® |
Available as | Capsules, oral powder sachets |
Aprepitant is known as a neurokinin-receptor antagonist. It is prescribed alongside other medicines (dexamethasone and 5HT3-receptor antagonists such as ondansetron) to help stop you from feeling or being sick after chemotherapy. It works by blocking the effect of a naturally produced chemical, called 'substance P'.
Before taking aprepitant
Back to contentsSome medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking aprepitant it is important that your doctor knows:
If you are pregnant or breastfeeding.
If you have any problems with the way your liver works.
If you have ever had an allergic reaction to a medicine.
If you have a rare, inherited blood disorder called porphyria.
If you are taking any other medicines, including any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines. Aprepitant interferes with a number of other medicines, including the 'pill' and the 'mini pill'.
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How to take aprepitant
Back to contentsBefore you start treatment, read the manufacturer's printed information leaflet from inside your pack. The manufacturer's leaflet will give you more information about aprepitant and a full list of side-effects which you may experience from taking it.
Take aprepitant capsules exactly as your doctor tells you to. You will be asked to take one 125 mg capsule one hour before your chemo treatment starts, and then one 80 mg capsule each morning for the following two days.
Swallow the capsules whole - it may help to take your doses with a drink of water. It is not important whether you take the capsules before or after food.
If your child has been prescribed oral powder sachets, the dose will be prepared and given to your child by a doctor or nurse in hospital.
If you forget to take a dose, contact your doctor for advice about what to do. Do not take two doses together to make up for a missed one.
Getting the most from your treatment
Back to contentsEven if you do not feel like eating or drinking, try to sip water regularly to prevent you from becoming lacking in fluid in the body (dehydrated).
Rather than trying to eat three main meals a day, try eating small, simple but nourishing snacks, every few hours.
If you are using hormonal contraception (this includes the 'pill' and the 'mini pill'), additional contraceptive precautions such as a condom will be required while you are on aprepitant, and for two months afterwards. If you need further advice about this, speak with your doctor or pharmacist.
If you buy any medicines, check with a pharmacist that they are suitable to take with your other medicines. This is because many other medicines can interfere with aprepitant and therefore may not be recommended for you.
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Can aprepitant cause problems?
Back to contentsAlong with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with aprepitant. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.
Common aprepitant side-effects - these affect fewer than 1 in 10 people who take this medicine | What can I do if I experience this? |
Headache | Drink plenty of water and ask a pharmacist to recommend a suitable painkiller. If the headaches continue, let your doctor know |
Feeling tired, sleepy or dizzy | Do not drive and do not use tools or machines if affected |
Constipation | Try to eat a well-balanced diet, and drink several glasses of water each day |
Loss of appetite, hiccups, indigestion | If troublesome, speak with your doctor |
Changes to some blood tests | Your doctor will check for this |
If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.
How to store aprepitant
Back to contentsKeep all medicines out of the reach and sight of children.
Store in a cool, dry place, away from direct heat and light.
Important information about all medicines
Back to contentsImportant information about all medicines
Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.
This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.
If you are having an operation or any dental treatment, tell the person carrying out the treatment which medicines you are taking.
Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.
If you have any questions about this medicine ask your pharmacist.
Report side effects to a medicine or vaccine
If you experience side effects, you can report them online through the Yellow Card website.

Unsure about mixing medicines?
Check for possible interactions between medicines, supplements and foods before taking them together.
Frequently asked questions
What is 'substance P' and why does blocking it help with sickness?
Aprepitant works by blocking a natural chemical in your body called 'substance P'. This chemical is involved in the signals that cause nausea and vomiting, especially after chemotherapy. By blocking its effect, aprepitant helps to prevent these unwanted symptoms.
Can I take aprepitant if I have liver problems?
If you have any problems with how your liver works, it's important to tell your doctor before starting aprepitant. They will need to know this information to determine if aprepitant is suitable for you or if extra care needs to be taken during your treatment.
What should I do if I forget to take a dose of aprepitant?
If you miss a dose of aprepitant, you should contact your doctor for advice on what to do. It is important not to take two doses together to try and make up for the one you missed.
Why is it important to prevent dehydration while taking aprepitant?
Chemotherapy can make you feel unwell, and it's easy to become dehydrated, meaning you lack enough fluid in your body. Even if you don't feel like eating or drinking, regularly sipping water is important to prevent dehydration, which can make you feel even worse.
Are there any specific dietary recommendations while taking aprepitant?
While taking aprepitant, instead of trying to eat three large meals a day, it's often more helpful to try eating small, simple, but nourishing snacks every few hours. This can be easier to manage when you're feeling unwell.
Further reading and references
- Manufacturer's PIL, Emend® 80 mg, 125 mg hard Capsules; Merck Sharp & Dohme Limited, The electronic Medicines Compendium. Dated September 2022.
- Medicines Complete BNF 89th Edition; British Medical Association and Royal Pharmaceutical Society of Great Britain, London.
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About the authorView full bio

Helen Allen, MPharm
Pharmacist, Medical Author
MPharm
Helen Allen qualified as a Pharmacist in 1979 and spent 3 years as the drug information leaflets' author for EMIS.
About the reviewer

Sid Dajani
Sultan Dajani qualified at the London School of Pharmacy in 1994 and became the youngest elected member of the Royal Pharmaceutical Society council since its founding in 1842.
Article history
The information on this page is written and peer reviewed by qualified clinicians.
Next review due: 27 Jun 2027
28 Dec 2022 | Latest version
22 Oct 2013 | Originally published
Authored by:
Helen Allen, MPharm

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