Glossary of Terms Related to Parenteral Drug Technology

Absolute Rating
This is the rating of a filter that tells the size of the largest spherical particle it can completely stop. For example, an absolute 0.2 µm filter will not let any particle 0.2 µm or bigger pass through. It ensures complete removal of particles above the stated size.

Action Level
A set microbial or particle limit. If this level is exceeded in cleanroom air or on surfaces, it indicates a possible contamination problem. When this happens, immediate investigation and corrective action are required to protect product safety.

Air Lock
A small enclosed room with interlocking doors, used between different cleanroom areas. It helps maintain pressure differences and prevents contamination when people or equipment move between areas.

Alert Level
A lower, early warning limit for microbes or particles. Crossing this level doesn’t mean contamination has already happened, but it signals that conditions may be worsening and need closer monitoring.

Ampule
A sealed glass container that holds sterile liquid drugs. After filling, its neck is melted shut with heat. It ensures drug protection but must be carefully opened to avoid glass particles contaminating the drug.

Antimicrobial Preservative
Chemicals added to multi-dose injectable drugs to stop microbial growth after the container is opened. Examples include phenol, benzyl alcohol, and parabens. These keep the product safe for repeated use.

Antioxidants
Substances added to drugs to prevent damage by oxygen. For example, vitamin C (ascorbic acid) or sodium bisulfite stop oxidation reactions that could make a drug ineffective.

Aseptic
A condition where harmful microorganisms (germs that cause disease) are completely absent. It is not the same as sterile — aseptic means free from harmful microbes, while sterile means free from all living microbes.

Aseptic Processing
A drug manufacturing method where the product is filtered to remove microbes and then filled into sterile containers in a clean environment, without using heat or other terminal sterilization methods.

Autoclave
A machine that uses steam under pressure to kill microorganisms. At 15 psi above normal pressure, steam reaches 121 °C, which is hot enough to sterilize most parenteral products and equipment.

Barrier
A physical separation between the sterile area and the surrounding clean area. Unlike an isolator, a barrier still exchanges filtered air with the surrounding area but reduces the risk of contamination.

Bioburden
The number of live microorganisms present on a material, container, or product before sterilization. It shows how "contaminated" something is before cleaning or sterilization.

Biological Indicator
A test tool that contains highly resistant microorganisms on a strip, container, or solution. It is placed inside a sterilizer to check if the sterilization process is powerful enough to kill them.

Bubble Point
A filter integrity test that measures the pressure at which air bubbles can pass through a wet membrane filter. This confirms whether the filter pores are intact and performing properly.

Buffers
Substances added to solutions to keep the pH stable, even if acids or bases are introduced. A stable pH is very important to keep many drugs effective and soluble.

Chelating Agents
Chemicals that “grab” and bind metal ions in a solution, preventing them from causing problems such as oxidation or forming insoluble particles. A common example is EDTA.

Class X
A cleanroom standard. For example, Class 100 means there are no more than 100 particles of 0.5 µm or larger per cubic foot of air. Lower numbers mean cleaner rooms.

Clean Room
A specially designed and controlled room where air, surfaces, and equipment are kept very clean. It prevents both particle and microbial contamination of drug products.

Colony Forming Unit (CFU)
A unit used in microbiology to count microorganisms. When microbes are placed on a growth medium, each single cell grows into a visible colony — this colony is called a CFU.

Coring
When a needle punctures a rubber stopper, a small piece of rubber may be torn out and fall into the solution. This is called coring and can contaminate the drug.

Critical Area
The most protected zone in cleanrooms where sterile drugs and materials are exposed. It is carefully designed to maintain sterility.

Critical Surfaces
Surfaces (like stoppers, vial mouths, filling nozzles) that directly touch the sterile drug or container. They must always remain sterile during production.

D-Value
The time required at a certain temperature (or radiation dose) to kill 90% of a specific microorganism population. It shows how resistant microbes are to sterilization.

Disinfection
A cleaning process that reduces the number of harmful microorganisms on surfaces to a safe level, though it may not kill all spores.

Endotoxin
Toxic substances released from certain bacteria when they die. Even if the bacteria are dead, endotoxins can cause fever and harmful reactions in patients.

HEPA Filter
A High Efficiency Particulate Air filter that removes 99.97% of particles 0.3 µm and larger. These are standard in cleanrooms and laminar flow hoods.

Isolator
A completely sealed and decontaminated chamber with very clean air (ISO 5 or better). It separates the product from the external environment, preventing contamination.

• Closed Isolator: Fully sealed, materials transferred aseptically.

• Open Isolator: Allows continuous transfer of materials through specially designed openings.

Laminar Flow
A smooth, straight airflow that moves in parallel lines at a constant speed. This prevents turbulence and reduces contamination risks in cleanrooms.

Lyophilization
Also called freeze-drying. A process where a drug solution is frozen, and water is removed by sublimation under vacuum. This makes stable powders that can be stored for longer.

Media Fill
A test where growth medium (instead of drug) is filled into containers under the same conditions as real production. It checks if aseptic operations can keep the medium sterile.

Micron (µm)
A unit of length equal to one millionth of a meter. Commonly used to describe particle sizes and filter pore sizes.

Needle Gauge
A number that indicates the needle’s thickness. A higher gauge means a thinner needle. For example, an 18-G needle is thicker than a 24-G needle.

Nominal Rating
A filter rating that tells what percentage of particles of a certain size are trapped. Unlike absolute rating, it does not guarantee full retention of those particles.

Overkill Sterilization Process
A sterilization method that provides much more microbial destruction than required — usually a 12-log reduction. It ensures an extremely high margin of safety.

Parenteral
A drug given by injection (not oral, nasal, skin, or rectal routes). Parenteral drugs must be sterile, free of pyrogens (fever-causing substances), and free of particles.

Pyrogen
Substances, often from bacteria, that cause fever when they enter the body. They must be removed from injectable drugs.

Reverse Osmosis
A water purification method where pressure pushes water through a special membrane. The membrane blocks impurities like ions, microbes, and particles, allowing only pure water to pass through.

Sterile
Completely free from any living microorganisms. A stronger condition than aseptic.

Sterility
A high level of assurance that a drug or product contains no viable microorganisms.

Sterility Assurance Level (SAL)
A probability measure of sterility. For example, SAL 10⁻⁶ means there is only 1 in 1,000,000 chance the product is contaminated.

Surface Active Agents
Chemicals that reduce surface tension between liquids or between liquid and solid, helping substances mix better. Examples include polysorbate 80 and sodium lauryl sulfate.

Terminal Sterilization
Sterilization carried out on the final packaged product, making it completely sterile at the end of manufacturing.

Tonicity Agents
Substances added to injectable solutions to make them isotonic (same osmotic pressure as body fluids). This prevents pain or cell damage at the injection site. Examples include sodium chloride and mannitol.

ULPA Filter
An Ultra-Low Penetration Air filter that removes 99.999% of particles 0.3 µm and larger. It provides even cleaner air than a HEPA filter.

Validation
A documented and scientific process that proves a method or system consistently works as intended and produces high-quality products.

 Prepared and Edited by: Dr. R. S. R=Tade

Credit/Reference: Akers, M.J., 2016. Sterile drug products: formulation, packaging, manufacturing and quality. CRC Press.