PDA Technical Glossary

PDA Technical Glossary

PDA Technical Reports are highly valued membership benefits because they offer expert guidance and opinions on important scientific and regulatory topics and are used as essential references by industry and regulatory authorities around the world. These reports include terms which explain the material and enhance the reader’s understanding.

The database presented here includes the glossary terms from all current technical reports. The database is searchable by keyword, topic, or by technical report. Each definition provided includes a link to the source technical report within the  PDA Technical Report Portal.

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Excipient
A component of a drug formulation that has no active pharmacologic function. Excipients are commonly used in drug formulations as modulators of pH or osmolality for parenteral administration and as stabilizers for APIs. (TR54-4) An ingredient added intentionally to the drug substance that should not have pharmacological properties in the quantity used. (TR57) Inactive pharmaceutical ingredients in a product formulation that are responsible for the product’s manufacturability and physicochemical attributes. (TR67) (TR88)
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Formulation
A listing of the ingredients and composition of the dosage form. (TR38) The percent composition of ingredients in a product. (TR67)
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Over-the-Counter (OTC) Drug Products
Drug products sold in drug stores directly to customers without a physician’s prescription. (TR67)
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Water Activity (Aw)
Water Activity, Aw is the ratio of the vapor pressure of water in a product (P) to the vapor pressure of water in a product (P) to the vapor pressure of pure water (Po) at the same temperature. It is numerically equal to 1/100 of the RH generated by the product in a closed system. It is a measure of the free or available moisture in the material. Note: Water activity ≠ water content. RH can be calculated from direct measurements partial vapor pressure or dew point, or from indirect measurements by sensors whose physical or electric characteristics are altered by the RH to which they are exposed. Microorganisms need available water within a pharmaceutical product, as well as nutrients and minerals, to proliferate. Water activity, and not water content, is a better measure of the free water, in contrast to bound water that microbial cells require for metabolic activity and osmotic regulation. Effects of reduced Aw on microbial growth include a longer lag phase, slower growth rate, lower numbers of organisms in the stationary phase, and reduced microbial toxin production; below a specified Aw for an organism, microbial growth will not occur. (TR55) (TR67)
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