An excipient is an inactive ingredient which is added to a pharmaceutical compound. There are a number of reasons to use excipients, ranging from a desire to conceal unpleasant flavors to the need to precisely control dosages. As a general rule, drug companies must be able to prove that an excipient is safe for use before they can sell a drug which contains the product, and inactive ingredients may need to be listed on drug labels to comply with the law.
People have been using excipients in drug delivery for centuries. Historically, for example, medicines were often mixed with honey or syrup to mask the flavor so that children would take them. This use of excipient conceals flavor and eases delivery. Other excipients may be added to drugs as diluents, in the case of drugs with potent active ingredients, to make it easier to provide accurate doses by making the medicine more bulky.
An inactive ingredient may facilitate the absorption of a drug into the body, or slow the rate at which a drug is absorbed, in the form of a time release coating which allows the drug to dissolve slowly. Other excipients may make drugs physically easier to swallow, or facilitate the breakdown of the drug once it reaches the right area of the body. Excipients can also act as binders, holding the ingredients in a drug together so that it can be dispensed properly.
Some drugs tend to separate or lose efficacy if they are kept in storage, in which case the excipient may act as a preservative to keep the drug potent. Other drugs lose action quickly when they are blended with an excipient, in which case the active and inactive ingredients may be packaged separately and blended as needed. This is common with drugs utilized in intravenous administration, which often come in the form of powders which must be mixed with intravenous fluids for administration.
Inhalers, sprays, and creams utilize excipients for their delivery method. Inhalers, for example, contain propellants which aerosolize the drug and make sure that it is delivered evenly, while topical creams are typically made with an inactive cream base to which the active ingredients are added.
People with allergies need to be careful about inactive ingredients in medicine, because allergens may be involved in the production of some inactive ingredients. Corn, wheat, dairy, and eggs are all used to manufacture medications. In patients with allergies, it may be necessary to specifically request a brand name known to be safe rather than a generic version to ensure that a medication will not cause an allergic reaction.