Definition of Excipients

Excipients are components in a drug formulation having a functional purpose related to the performance of a drug product. 


Excipients can be macromolecules as albumin, or substances such as amino acids and sugars that are used in drug and biological products. 


Functional Properties of Excipients

With advances in the technology of drug dosage forms and drug delivery systems, functional properties including preservation, solubility, release control and disintegration have become more critical to issues of safety and bioavailability in modern drug products. 


Accordingly, a more appropriate definition for an excipient is:


“A substance other than the active ingredient, which has been appropriately evaluated for safety and is included in a drug delivery system to:

1) aid in  the processing of drug delivery system during the manufacturing;

2) protect, support, or enhance stability,(formulation feasibility) bioavailability, or patient acceptability;

3) aid in  product identification; or

4) enhance any other attribute of the overall safety and effectiveness of the drug during storage and use”


Recent advances in formulation technology have increased the need for new materials with enhanced properties to facilitate and improve active delivery. 


Novel Excipients

Excipient(s) used for the first time in a drug product or in a new route of administration are currently considered “novel .”

A novel excipient generally refers to an inactive ingredient that has not been previously used in an approved drug product. 


However, regulators may view an excipient that has not been used in a particular route of administration or at levels above the precedence of use in an approved drug product as “novel.” 


Even if an excipient has been extensively used in other approved, non - pharmaceutical applications, such as food or over-the-counter ( OTC) products, it is still considered “novel” when used in drug products subject to regulatory approval. 


In general, excipient users are reluctant to use a novel excipient in a drug product as there is no certainty that a regulatory agency would find the available excipient safety information adequate. 


This uncertainty is greater for generic drugs as nonclinical and clinical studies are not required for regulatory approvals.


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