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PDA Glossary

PDA Glossary of Pharmaceutical and Biotechnology Terminology

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.

Browse Terms by Title


Browse Terms by TR #

  • Active Pharmaceutical Ingredient (API)

    Synonym: Drug Substance. (TR14) (TR42)

    A substance or mixture of substances that, when delivered in a finished drug product, directly affects the structure or function of the body. (TR54-4)

    Any substance or mixture of substance intended to be used in the manufacture of a drug (medicinal) product and that, when used in the production of a drug, becomes an active ingredient of the drug product. Such substances are intended to furnish pharmacological activity or other direct effect in the diagnosis, cure, mitigation, treatment, or prevention of disease or to affect the structure and function of the body. Note: also known as Drug Substance. (TR29) (TR56) (TR41) (TR54-3) (TR60)

    Any substance or mixture of substances intended to be used in the compounding of a drug preparation, thereby becoming the active ingredient in that preparation and furnishing pharmacological activity o other direct effect in the diagnosis, cure, mitigation, treatment, or prevention of disease in humans and animals or affecting the structure and function of the body. (TR63) (TR70)

    Any substance or mixture of substances intended to be used in the manufacture of a drug product, and that when used in the production of a drug, becomes an active ingredient in the drug product. Such substances are intended to furnish pharmacological activity or other direct effect in the diagnosis, cure, mitigation, treatment or prevention of disease, or to affect the structure and function of the body. (TR74)

  • Bacteriophage

    A bacteriophage is any one of a number of viruses that infect bacteria. The term is commonly used in its shortened form, “phage”. (TR41) (TR 47)

  • Bracketing

    A demonstration of unit operation performance at two different values of a given parameter (e.g., ionic strength, dwell time or temperature), allowing the use any values of that parameter falling within this range. (TR41)

  • Bubble Point

    The measured differential gas pressure at which a wetting liquid (e.g., water, alcohol, product) is pushed out of the largest pores of a wetted porous membrane, and a steady stream of gas bubbles or bulk gas flow is detected.(TR15) (TR26)

    The minimum pressure at which a wetting liquid is pressed out of the pore system of a membrane while forming a steady bubble chain. (TR41)

  • Capsule Filter

    Compact, self-contained filter assembly. Generally, the whole assembly is disposable. (TR26) (TR41)

  • Cartridge Filter

    Filter elements encased in a housing. Generally, the filter elements are disposable while the housing units are multi-use. In a few cases, both filter and housings are disposable. (TR26) (TR41)

  • Compatibility (Filter)

    The ability of a filter to be used with a particular process fluid without a change in the inherent properties of the filter. (TR41)

  • Dextrans

    Complex, branched, high molecular weight polysaccharides made of many glucose molecules joined into chains of varying lengths and branches. (TR41)

  • Diffusion Test (or Forward Flow Test)

    A test for membrane integrity that involves measuring the rate of gas diffusion through a liquid-wetted membrane.(TR15)

    An integrity test in which a filter is subjected to differential gas pressures below the bubble point and gas molecule migration through the water-filled pores of a wetted membrane is measured. This behavior follows Fick’s Law of Diffusion (i.e., the gas diffusional flow rate for a filter is proportional to the differential pressure and the total surface area of the filter). (TR41)

  • Direct Flow Filtration (DFF) or Normal Flow Filtration (NFF)

    In direct flow filtration, all fluid is directed through the membrane in a single pass. (TR41)

  • Endogenous Virus-Like Particles – (e.g., Type C endogenous retroviruses)

    Virus-like entity whose genetic material is stably integrated into the germ line of an organism or cell line. Cell lines (notably CHO) may constitutively produce virus-like particles, which are typically noninfectious but still of safety concern. Model retroviruses are generally used as surrogates to measure virus-like particle clearance. (TR41)

  • Enzyme-Linked Immunosorbent Assay, or ELISA

    A biochemical technique used to detect or measure the presence of an antibody or an antigen in a sample. (TR41) (TR47)

  • Extractable

    A chemical component that is removed from a material by application of an artificial or exaggerated force (e.g., solvent, temperature, time). The term extractable is often erroneously used to describe a leachable. (TR14) (TR15) (TR26) (TR41) (TR45)

    Chemical substances that can be extracted from components of material process fluid contact surfaces by exertion of an exaggerated force (e.g., organic solvent, extreme elevated temperature, ionic strength, pH, contact time, etc.) Extractables may represent most but not all of the potential leachables that may be seen in process fluids. (TR66)

    Extractables are organic and inorganic chemical entities that can be released from a pharmaceutical packaging/delivery system, packaging component, or packaging material of construction under laboratory conditions. (TR54-4)

    Organic or inorganic chemical entity that is forced out of container closure system materials and components under laboratory experimental conditions. (TR73)

  • Feed (or Load or Feedstock or Feedstream)

    The fluid introduced into a process. (TR41)

  • Filtration

    A process of removing particles from a fluid by passing it through a permeable material, such as a membrane film. (TR41)

    The process by which particles are removed from a fluid by passing the fluid through a porous material. (TR26)

  • Flux Decay

    Instantaneous or current flux relative to initial or buffer flux. (TR41)

  • GMPs

    Best practices in manufacturing of pharmaceuticals or biopharmaceuticals. From a regulatory standpoint, GMPs are regarded as the minimum current good manufacturing practice for methods to be used in, and the facilities or controls to be used for, the manufacture, processing, packaging, or holding of a drug to assure that such drug meets requirements of safety, identity and strength and meets the quality and purity characteristics that it purports or is represented to possess. (TR41) (TR 79)

  • Irradiation

    The process by which an item is exposed to ionizing radiation (typically gamma) to reduce or eliminate bioburden. (TR41)

  • Limit of Detection (LOD)

    The lowest concentration of microorganisms in a test sample that can be detected, but not necessarily quantified, under the stated experimental conditions. (TR33)

    The lowest amount of analyte in a sample that can be distinguished from the absence of analyte. (TR41)

    The lowest concentration of analyte that can be unambiguously detected in a sample. For qualitative and for quantitative NAT methods, this value is conventionally expressed as a 95% positive cut-off value, representing the target concentration detected in 95% of repeated tests using a certain assay. (TR50)

  • Log Titer Reduction (LTR) or Log Reduction Value (LRV)

    The virus reduction factor of an individual purification or inactivation step is defined as the log10 of the ratio of the virus titer or total load in the prepurification material and the virus titer or load in the post-purification material which is ready for use in the next step of the process. (TR41)

  • Monodispersed particles

    Particles of uniform size in a dispersed phase. In the case of viruses, this term refers to free virus particles not agglomerated to other viruses or proteins in solution. (TR41)

  • Multiplicity of Infection (MOI)

    The average number of infectious units added per cell in an infection. (TR41)

  • Nominal Pore Size Rating

    A filter rating with an arbitrary value, indicating a particulate size range at which the filter manufacturer claims the filter removes some percentage. Nominal ratings vary from manufacturer to manufacturer and may not be suitable to compare filters among manufacturers. Processing conditions, such as operating pressure and concentration of contaminant may have a significant effect on the retention efficiency of the nominally rated filters. (TR41)

  • Nonspecific Model Virus

    A virus used for characterization of viral clearance of the process when the purpose is to characterize the capacity of the manufacturing process to remove and/or inactivate viruses in general (i.e., to characterize the general viral clearance capacity of the purification process.) (TR41)

  • Optical Density (OD)

    A unitless measure of the absorption of light of a given wavelength in media of a given path length. (TR41)

  • Permeability

    The degree to which a fluid will pass through a permeable substance under specified pressure and temperature conditions. (TR41) (TR26)

  • Permeate

    The fluid which passes through a membrane. (see also filtrate) (TR41)

  • Polymerase Chain Reaction (PCR)

    A technique widely used in molecular biology in which a DNA polymerase is used to amplify a piece of DNA by in vitro enzymatic replication. As PCR progresses, the DNA thus generated is itself used as a template for replication. This sets in motion a chain reaction in which the DNA template is exponentially amplified. This technique may be used to quantify virus. (TR41) (TR47)

  • Pore

    The channel(s)/path(s) in a membrane through which a fluid or a gas may pass. (TR41) (TR26)

  • Pore Size

    The size of the channel passages through the filter media. (TR41)

  • Porosimetry (Gas-Liquid and Liquid-Liquid)

    An analytical technique used to determine various quantifiable aspects of a material’s porous nature, such as pore diameter, total pore volume, surface area, and bulk and absolute densities. (TR41)

  • Pressure Hold Test (or Leak Test)

    A test for leaks and gross defects in which the system is held at a defined pressure for a defined time. Failure is indicated by the observation of a steady stream of air bubbles downstream of the filter. (TR41)

  • Process Characterization of Viral Clearance

    Viral clearance studies in which nonspecific model viruses are used to assess the general virus clearance capacity of the manufacturing process to remove and/or inactivate viruses. (TR41)

  • Process Evaluation Studies of Viral Clearance

    Viral clearance studies in which relevant and/or specific “model” viruses are used to determine the ability of the manufacturing process to remove and/or inactivate these viruses. (TR41)

  • Processing Time

    The duration of time for a phase of a manufacturing unit operation or the entire operation. (TR41)

  • Reduction Factor

    The viral clearance capacity of a particular unit operation. It is typically calculated as the log10 (virus input ÷ virus output). (See also log titer reduction or log reduction value.) (TR41)

  • Relevant Virus

    A virus used in process evaluation studies that either is the identified virus, or of the same species as the virus known to or likely to contaminate the cell substrate or any other reagents or materials used in the production process. (TR41)

  • Size Exclusion

    A technique which separates particles based on diameter. (TR41)

  • Specific Model Virus

    Virus that is closely related to the known or suspected virus (same genus or family), having similar physical and chemical properties as those of the observed or suspected virus. (TR41)

  • Steam-in-Place (SIP)

    The process of applying clean pressurized steam to a stationary piece of equipment in order to sterilize it. (TR41)

  • Sterilizing Grade Filter

    A filter intended for terminal processing of sterile liquids that has been tested under worst-case actual processing conditions for the ability to retain a minimum challenge of 107 cells of Brevundimonas diminuta per cm2 of filter area. (TR41)

    A filter that reproducibly removes all test microorganisms from the process stream, producing a sterile effluent. (TR75)

    A filter that reproducibly removes test microorganisms from the process stream, producing a sterile filtrate. (TR26)

  • Surrogate Fluid

    A model process fluid used in a small-scale validation study. The fluid is intended to either match or resemble an actual process fluid as closely as is feasible. (TR41)

  • Tangential or Cross Flow Filtration (TFF or CFF)

    Filtration in which a fluid (feed) stream runs tangential to a membrane. A pressure differential causes some fluid to pass through the membrane. (TR41)

  • Tissue Culture Infectious Dose – TCID50

    The dilution of virus that results in the probability of infection of 50% in replicate tissue-culture inoculations. (TR41)

  • Titer

    The concentration of infectious virus calculated, taking into account the dilution factor. (TR41)

  • Toxicity

    The capacity of a substance to confer morbidity or mortality. In the context of virus assays, the ability of a buffer or other process components to kill or otherwise harm the functionality of indicator cell lines. This is independent of the infection by the virus. (TR41)

  • Transmission Electron Microscopy (TEM)

    A microscopy technique whereby a beam of electrons is transmitted through an ultra-thin specimen, interacting with the specimen as it passes through it. An image is formed from the electrons transmitted through the specimen, which are magnified and focused by an objective lens, and appear on an imaging screen. (TR41)

  • Ultrafiltration Membranes

    Membranes that retain particles whose sizes are measured by molecular weight, with retention ranges from 1,000 to 1,000,000 (Daltons). (TR41)

  • Viral Clearance

    Elimination of a target virus by removal of viral particles or by inactivation of viral infectivity. (TR41)

  • Viral Inactivation

    Reduction of virus infectivity caused by chemical or physical modification. (TR41) (TR83)

  • Virus

    A simple, potentially pathogenic organism composed of a single type of nucleic acid (DNA or RNA) encased in a protein shell (called a capsid) and, in some cases, a lipid membrane (called an envelope). Viruses are incapable of independent replication and therefore must infect a host cell in order to propagate. (TR41)

    Obligate, intercellular, replicating, infectious agents that are potentially pathogenic, possessing only a single type of nucleic acid (either RNA or DNA). They use the host cells for propagation as they are unable to grow independently, for example by binary fission, and multiplying their genomic material. (TR47) (TR83)

  • Virus Removal

    Physical separation of virus particles from the intended product. (TR41)

  • Volumetric Throughput (Vmax)

    The maximum volume that can be processed through a filter area. It is the volumetric capacity of the filter for a given process fluid and generally expressed in L/m2. (TR41) (TR47)