What Are Drug Excipients?

To find out which excipients are contained in a drug, all you have to do is look at the package insert or the labeling. In this article, we'll tell you how to find out more about drug excipients.
What Are Drug Excipients?

Last update: 13 March, 2021

You’ve probably already heard the expression “drug excipients” because you’ve seen it many times, perhaps while reading the package insert of a drug. But do you know what it refers to?

Drug excipients are the components of the formulation or a medication, aside from the active ingredient, which is the therapeutic molecule. In this sense, a drug consists mainly of an active ingredient and excipients.

The purpose of these excipients is to achieve the desired dosage form.

The dosage form is, therefore, the individualized arrangement to which the drugs and excipients are adapted. In other words, it’s the physical appearance given to drug substances to facilitate their administration.

For example, a syrup is one pharmaceutical form for oral administration, but pills are a different pharmaceutical form.

In short, manufacturers combine excipients with the active ingredients of drugs in different pharmaceutical forms (for oral, intravenous, anal, nasal administration, etc.) to synthesize a drug, which is the combination of the mentioned substances.

Let’s take a closer look.

What are drug excipients for?

A pill bottle containing a variety of white pills.

Excipients have the function of facilitating the preparation, storage, and administration of drugs. They’re also the only components that may differ between a brand-name drug and a generic drug.

Here are some of the most common types of excipients:

  • Binders: Their function is to hold the components together. Some of the most common are starches, sugars, lactose, or sugars such as xylitol.
  • Diluents: Diuents fill the contents of a tablet or capsule to achieve a presentation that’s convenient for consumption. Vegetable cellulose is a very common excipient when it comes to tablets or hard gelatin capsules.
  • Disintegrants: These excipients improve the release of active ingredients in the digestive tract.
  • Lubricants: Essential in preventing lumps from forming or ingredients from sticking to the machines when manufacturing them. Some of the most common substances for this purpose are common minerals such as talc. Steroid grease also serves as a lubricant.
  • Coatings: These excipients protect the ingredients from atmospheric agents such as air or moisture. They also make it easier to swallow tablets with a bad taste. A cellulose coating that doesn’t contain any allergenic substances is most common.
  • Sweeteners: The main function of these excipients is to make the tablets easier to swallow by improving their taste.
  • Flavoring and colorants: These improve the organoleptic properties of the drugs and, as a result, improve compliance with the therapeutic regimen.

How do excipients appear on the package leaflet of a drug?

A woman reading the information about a medication.

Excipients are normally inert substances, i.e. they don’t have any effect on the body. However, it’s sometimes possible that they may have a recognized action or effect, such as allergies or intolerances.

It’s for this reason that you should always find out about the composition of medicine and ensure that you use it correctly.

To find out which excipients a drug contains, you only have to look at the package leaflet or the labeling. In the former, you’ll find a full description of the excipients. In other words, first with the International Nonproprietary Name (INN), which is the name by which it’s known, followed by the letter “E” -which doesn’t always appear- and finally its corresponding number.

However, on the product labeling, it may only appear with the letter “E” and the corresponding number. In other words, the common name doesn’t have to appear.

Take, for example, the excipient titanium dioxide. The package insert should state “titanium dioxide E171” for drugs containing this excipient.

Thanks to this information on the package insert, many health problems can be prevented. For example, celiac patients can check whether the formulation contains gluten. Similarly, patients with lactose intolerance can see if any components affect them.


Excipients are essential for the manufacturing of drugs. They improve the taste, appearance, absorption, and distribution of the preparation.

Since some of them can produce allergic or intolerant effects, you must read the package insert or ask your doctor or pharmacist about its composition before taking any medication.

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  • Balbani, A. P. S., Stelzer, L. B., & Montovani, J. C. (2006). Excipientes de medicamentos e as informações da bula. Revista Brasileira de Otorrinolaringologia. https://doi.org/10.1590/s0034-72992006000300018
  • Robles, L. V. (2011). Los excipientes y su funcionalidad en productos farmacéuticos sólidos; Revista Mexicana de Ciencias Farmaceuticas.
  • Villafuerte R., L. (2011). Los excipientes y su funcionalidad en productos farmacéuticos sólidos. Revista Mexicana de Ciencias Farmaceuticas.