What Are Excipients in Medications?

The Inactive Ingredients That Play a Number of Different Roles in Drugs

Assorted medical pills and tablets in shape of drug capsule
Getty Images/Andrew Brookes

When drug manufacturers create a medication, it has several ingredients. Obviously, a drug will contain active ingredients — the chemical compounds that treat the condition for which you're actually taking the medication. But it also will contain inactive ingredients. These inactive ingredients are called excipients.

What Are Excipients?

Excipients are included in almost all prescription and over-the-counter medications.

They can include dyes, flavors, substances to bind the pills together, lubricants and preservatives.

Some excipients help a drug to disintegrate into particles small enough to reach the bloodstream more quickly. Others protect the stability of the product so it will be at maximum effectiveness at time of use. Excipients also may prevent a drug from dissolving too early in your system, protecting against stomach upset.

They are supposed to be inert, which means they don't have any effect on you, but some can cause symptoms by themselves — and potentially allergic reactions — or interact with the drug's active ingredients to cause unexpected results.

The word "excipient" comes from the Latin verb excipere, which means "to take out."

How Are Excipients Used in Medications?

The U.S. Food and Drug Administration requires approval of excipients used in new medications. Among other things, an inert ingredient must:

  • Be safe in the amount used in the drug
  • Not affect the bioavailability and performance of the drug
  • Be manufactured in accordance with good standards

The FDA has approved plenty of excipients: There were 13,045 inactive ingredients in the FDA's database in early 2016. They ranged from acacia (which is a gum-based thickener) to zinc sulfate.

Medication additives can take the form of flavorings. For instance, mandarin oil, lemon oil, and menthol are included in the list. Or they can be colorings like the inks that appear on the FDA's list in a variety of colors and forms.

Additives can be something most people would recognize (such as light mineral oil or fructose), or they can be something with a long, nearly incomprehensible chemical name, such as polyvinyl alcohol graft polyethylene glucol copolymer (3:1; 45000 MW) or linoleoyl macrogolglycerides.

The most common excipients include cornstarch, lactose, talc, magnesium stearate, sucrose, gelatin, calcium stearate, silicon dioxide, shellac and glaze.

Potential Problems with Excipients

Excipients in medications are supposed to be inert, which means they aren't supposed to react with a drug's active ingredients or cause reactions in the people taking the drug. However, in practice they don't always work as they should.

For example, calcium salts, which are used as fillers in medications, can cause your intestines to not absorb certain antibiotics as well.

The scientists who formulate medications must take potential interactions into account when designing the drugs.

In addition, it's certainly possible to be allergic or intolerant to "inert" ingredients in a medication. For example, many people are lactose intolerant, yet lactose frequently is used to formulate drugs. In addition, some people are allergic to corn, yet tablets and other drug formulations often contain cornstarch as a binder or filler. Finally, some people react to the coloring agents used in medications (and in food).

If you have concerns about the excipients used to make a particular medication, talk to your pharmacist about it. She has access to the entire ingredient list.


Dave RH. Overview of Pharmaceutical Excipients Used in Tablets and Capsules. Drug Topics. Oct. 24, 2008.

Hayward A et al. Pharmaceutical excipients - where do we begin? Australian Prescriber. 2011;34:112-4.

U.S. Food and Drug Administration. Inactive Ingredients Database. Accessed March 4, 2016.

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