Pharmaceutical Excipients

According to the European Pharmacopoeia, “an excipient is any component, other than the active substance(s), present in a medicinal product or used in the manufacture of the product. The intended function of an excipient is to act as the carrier (vehicle or basis) or as a component of the carrier of the active substance(s) and, in so doing, to contribute to product attributes such as stability, biopharmaceutical profile, appearance and patient acceptability and to the ease with which the product can be manufactured. Usually, more than one excipient is used in the formulation of a medicinal product.”

Excipients can be included for conferring a therapeutic enhancement on the active ingredient in the final dosage form such as facilitating drug absorption, for bulking up solid formulations that contain potent active ingredients in small amounts (Fillers & Diluents), for long-term stabilization (Preservatives), for optimized tablet compression or powder flowability during the manufacturing process, etc. Excipients may have many other functionalities such as: binders, viscosity agents, coatings for tablets, flavouring agents, disintegrants, colorants, lubricants, sweeteners, etc. A carefully-chosen excipient may also reduce manufacturing costs by being multifunctional.

Although excipients are often categorized as inert or inactive ingredients, excipient stability and impurities as well as material variability can influence drug product performance, for instance by potential chemical interactions with active pharmaceutical ingredients (API).

Preformulation studies can help determine how excipients influence the stability, bioavailability, and processability of the dosage forms.

The characterization of excipients properties should include not only a chemical characterisation (composition, purity), but also physicochemical testing by means of different techniques. Physical functional properties of excipients are determined by a complex interaction of parameters such as particle size, shape, density, surface area, and particle arrangement in the crystal lattice.

The figure here below gives an overview of the of the different tests described in the European Pharmacopoeia to assess the physical properties of particulate solids and the impact these determined properties may have on the final drug. For example, particle size distribution can be measured either by analytical sieving or by laser light diffraction. The particle size may have an impact on the mixing properties and consequently on the weight and content uniformity of a pharmaceutical dosage form.It may also influence the dissolution rate of a tablet. Particle flowability influences the processability of the formulation, while surface area directly impacts disintegration and dissolution.

Alfatestlab is equipped with all the analytical techniques necessary to support you in choosing the right excipient for your formulation. Contact us to discuss your analytical needs!


Charoo, N.A. Critical Excipient Attributes Relevant to Solid Dosage Formulation Manufacturing. J Pharm Innov 15, 163–181 (2020).



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