Excipients in medicines

Excipients or inactive ingredients in medicines

Key points about excipients in medicines

  • Excipients are extra substances found in medicines such as fillers.
  • They are often referred to as inactive ingredients.
  • Read about excipients in medicines including why they are added to medicines.
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Prescription and over the counter (OTC) medicines are made up of many ingredients. The part of the medicine that makes it work is known as the active ingredient, but inactive ingredients or ‘excipients’ are also added. 

Different medicines contain different excipients. See below: How to find out which excipients are in your medicines. 

If you need to avoid any excipients, tell your pharmacist when you are starting a new medicine or brand. Different brands of the same medicine may use different excipients, especially preservatives and colourants, so there could be an alternative available.

  • To improve the taste – sugar, artificial sweeteners or flavouring may be added to make them taste better.
  • To improve the texture – thickening agents may be added to make liquid medicines easier to pour.
  • To dissolve the medicine – small amounts of ethanol (alcohol) may be used to help dissolve a liquid into a liquid form.
  • To make them easier to handle – powders or fillers can be used to make tablets large enough to handle, if the amount of active ingredient is very small.
  • To make them work better – extra ingredients may be added to tablets to help them break down properly in the stomach.
  • To make them last longer – preservatives might be added to improve the shelf-life of a medicine.

Different medicines contain different excipients. All medicines approved in New Zealand have been assessed by Medsafe, which includes reviewing the excipients contained in medicines to ensure they meet acceptable quality and safety standards. 

Some people may want to avoid some types of excipients. Tell your doctor or pharmacist if you need to avoid an excipient, as they may be able to provide a different version of the medicine. Note, most medicines have very small amounts of excipients that are unlikely to cause any problems.

Tell your pharmacist if you need to avoid any of the following excipients
  • Peanut oil (also called Arachis): If you are allergic to peanuts, tell your pharmacist so that a different formulation can be provided.
  • Soya oil: If you are allergic to peanuts, you may also be allergic to soya. Tell your pharmacist so that a different formulation can be provided.
  • Aspartame: This is a sweetener used instead of sugar. People who have phenylketonuria should avoid aspartame because it is converted to phenylalanine in the body.
  • Gluten: Most medicines are gluten-free. However, some medicines may contain wheat starch, which people with coeliac disease need to avoid. See gluten in medicines.
  • Colourings: Medicines may contain colouring agents that some people are sensitive to. Colour-free forms are available for some medicines.
  • Sugar: People with diabetes need to be aware of sugars in medicines. Sugar-free forms may be available.
  • Preservatives: Preservatives such as parabens (also known as methyl, ethyl or propyl hydroxybenzoates) have been linked to potential allergic reactions. Some preservatives need to be avoided in very young and premature babies, such as sodium benzoate. 

The following excipients are unlikely to cause any problems but some people may prefer to avoid them.


People with some inherited conditions may need to avoid medicines containing lactose. These are rare and include galactose intolerance, total lactose deficiency or glucose–galactose malabsorption. The amount of lactose in tablets is very small, and it is unlikely to have an effect for people who are lactose intolerant.


Ethanol (the scientific name for alcohol) may be used to help a medicine dissolve to make a liquid medicine. Medicines for children do not contain ethanol. Adult medicines may contain it, but the amount is usually very small.

Propylene glycol

This is another form of alcohol, now rarely used. If your medicine contains it you should talk to your doctor or pharmacist before giving the medicine to any child under 5 years of age.

Animal-derived excipients

Some excipients, eg gelatin, are derived from animal products which vegetarians, vegans and people of particular faith may wish to avoid. Gelatin is sometimes used as the outer coating of capsules. Lactose is typically derived from animal milk and magnesium stearate is from vegetable sources.

Mannitol and sorbitol

These are artificial sweeteners used in sugar-free forms of medicines. Although these can cause soft or runny poos (diarrhoea), due to the small amount present in medicines, it is unlikely this will happen.

The excipients in a medicine are listed in its data sheet under the heading “Pharmaceutical Particulars”. Medicine datasheets are available on the Medsafe website. See their alphabetical list of data sheets(external link) or you can search for data sheets and consumer medicine information (CMIs) on the Medsafe website(external link). If you need help with this, ask your pharmacist to help you.

If you can't find the information you're looking for, or have any questions about this information, contact the pharmaceutical company named as the sponsor in the data sheet or consumer medicine information (CMI).

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Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

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