A few-letter (usually 2 to 4) shortcut for identifying a particular substance. For example, levonorgestrel is often abbreviated as LNG.

Apparent Volume of Distribution

A theoretical volume needed to contain the amount of an administered drug at the same concentration observed in blood plasma.


A description of the visual appearance of the compound, usually composing the state of matter and color.


A classification scheme for drug APIs based on the organ on which it acts and its chemical, medicinal, and pharmacological properties, controlled by the WHO Collaborating Centre for Drug Statistics Methodology (WHOCC).


The area under the curve of a plot of drug plasma concentration vs. time, representing the total drug exposure over time.


The amount of an administered dose of drug that remains unchanged and reaches circulation. Often represented by the symbol F.


Different preparations of a drug that are pharmacologically equivalent in the body.

Caco-2 Permeability

Caco-2 is a cancer cell line that is used in in vitro assays to estimate how well an orally-dosed drug is absorbed into the intestine.


The ability of a substance to cause cancer.


A unique numeric identifier designating one specific compound described in the scientific literature from 1957 to the present. The most common identifier for a chemical compound.


"Reference chemical structures, nomenclature and ontological classification" for compounds of biological interest, provided by the European Bioinformatics Institute of the European Molecular Biology Laboratory (EMBL-EBI).


"An open data resource of binding, functional and ADMET bioactivity data" provided by the European Bioinformatics Institute of the European Molecular Biology Laboratory (EMBL-EBI).


"A free chemical structure database providing fast text and structure search access."


The rate at which a substance is eliminated from the body, usually given in units of L/h or mL/min.

Conversion Efficiency

The dose of a prodrug that is pharmacologically equivalent to a different dose of its bioactive metabolite.


The mass of a specific volume of a substance.


An online database with information on drugs and drug targets.

ECHA InfoCard

A summary of information, provided by ECHA, on a particular chemical substance. The EC or list number is the primary substance identifier used by ECHA.

Enzyme Interactions

The interaction of a substance with an enzyme that is not the primary therapeutic target. This interaction may take different forms (the substance may be an agonist, antagonist, etc), and can result in side effects, drug-drug interactions, and so on.


The elimination of a drug or its metabolites from the body, commonly in the urine or feces.


The ability of a substance to damage genetic information within a cell, causing damage. Unlike a mutagen, the induced genetic damage from genotoxins does not necessarily result in genetic change passed on to progeny. All mutagens are genotoxic, but not all genotoxins are mutagenic.

GHS Code

A standardized classification and statement of hazards posed by a particular chemical or mixture.


The time it takes a substance to lose half its pharmacologic activity. Sometimes referred to as the biological or terminal half-life.

Henry's Law Constant

Henry's law states that the amount of a gas dissolved in a liquid is proportional to the partial pressure of that gas when in equilibrium with the liquid. The proportionality is Henry's law constant.


An identifier for chemical information, encoding molecular structure for use in databases and cheminformatics. The InChI key is a 27-character condensed digital representation of the InChI that is meant for web searching and is not human understandable.


A reason to use a certain medicine.

Inhibition of Ovulation

Amount of substance needed to inhibit ovulation in a user.


A website on pharmacological information provided by International Union of Basic and Clinical Pharmacology (IUPHAR) and the British Pharmacological Society (BPS).


An online database of information on biologically-relevant systems, including pathways, genes, drugs, enzymes, etc.


The amount of a substance that causes death in 50% of a population.


Also denoted as logKOW. The ratio of a compound in a mixture of octanol and water. A measure of the hydrophilicity or hydrophobicity of a compound. This property is frequently calculated, usually denoted as clogP.

Melting Point

The temperature (usually given as a range) at which a compound transitions from solid to liquid. The determination of melting point is sometimes used as a rough and non-specific measure of purity and chemical identity.

Menstrual Delay

Amount of substance needed to delay menstruation.


The transformation of a substance within the body, usually by enzymes.

Minimum Contraceptive Threshold

Minimum concentration of drug in the plasma needed to provide contraceptive efficacy.

Molecular Formula

The number of each atom of a specific element comprising a molecule.

Molecular Weight

The mass of a molecule. When the mass of one mole of a compound is given (usually in g/mol), it is known as molar mass.


The maximum recommended therapeutic dose (MRTD), or maximum recommended daily dose (MRDD), is "an estimated upper dose limit beyond which a drug’s efficacy is not increased and/or undesirable adverse effects begin to outweigh beneficial effects" which is "empirically derived from human clinical trials." {From Matthews, E.; Kruhlak, N.; Benz, R.; Contrera, J. Assessment of the Health Effects of Chemicals in Humans: I. QSAR Estimation of the Maximum Recommended Therapeutic Dose (MRTD) and No Effect Level (NOEL) of Organic Chemicals Based on Clinical Trial Data1. Curr. Drug Discov. Technol. 2004, 1 (1), 61–76.}


Capacity of a drug to induce changes in an organism's DNA that are retained and passed on to descendants. It is commonly measured by the Ames test.


Other names used to identify a particular compound.
USAN: United States Adopted Name
INN: International Non-proprietary Name
JAN: Japanese Adopted Name

NIST Chemistry WebBook

"This site provides thermochemical, thermophysical, and ion energetics data compiled by NIST under the Standard Reference Data Program." It may also provide information on IR or MS spectra and chromatography.

P-gp Binding

Permeability glycoprotein (also known as multidrug resistance protein 1, MDR1, P-glycoprotein 1, P-gp or Pgp) is a transporter protein expressed extensively in the small intestine, among other places. It can pump absorbed drugs or toxins out of a cell back into the lumen of the small intestine, thus reducing the adsorption of an oral drug.


"Archive-information about the 3D shapes of proteins, nucleic acids, and complex assemblies," funded by the National Science Foundation, the National Institutes of Health, and the Department of Energy.

Peak Plasma Concentration

The maximum concentration a drug reaches in the plasma after administration.


The ability of a solid to exist in more than one crystal structure.


An online repository of chemical information from the National Center for Biotechnology Information of the National Library of Medicine of the National Institutes of Health.


An online subscription database on chemical compounds and reactions.

Receptor Activity

The activity of a compound towards a specific receptor (e.g. progesterone, androgen, estrogen, glucocorticoid, or mineralocorticoid receptors).

Route of Administration

The method in which the drug is administered: through an oral pill, via injection (subcutaneous or intramuscular), as an implant, etc.

Safety Profile

A general summary of the affect on health of a drug.

Serum Protein Binding

When a drug enters circulation, it can potentially bind to a number of different proteins or circulate unbound. The less bound a substance is, the better it diffuses across cell membranes. Common proteins that bind drugs in plasma are serum albumin, sex hormone binding globulin (SHBG), and corticosteroid-binding globulin (CBG). Also referred to as plasma protein binding.

Side Effects

An effect of a drug other than the primary intended effect.


A line notation for chemical structures using ASCII.


The ability of a compound to dissolve in a particular solvent, usually water or an organic solvent such as hexane, ethanol, etc.

Specific Optical Rotation

The change in orientation of monochromatic, plane-polarized light by a compound in solution.

Storage Conditions

The recommended conditions under which to store a compound to prevent or reduce degradation.


The amount of time after the administration of a drug until the concentration of that drug reaches its maximum value (referred to as Cmax) in the blood plasma.

Target Pathways

Biochemical pathways affected by a particular substance.


Dose at which toxic effects occur in 50% of a population. For TD50 values from the Carcinogenic Potency Database, the values displayed specifically refer to carcinogenic potency, which is the dose resulting in an increase in carcinogenic response in 50% of a population.


The lowest dose of a substance known to elicit a toxic response in a population.

Transformation of Endometrium

Amount of substance needed to transform estrogen-primed endometrium into secretory endometrium.


The UNII is a unique identifier for a specific compound used in drug or biologic products. This number is generated by the Substance Registration System (SRS) of the FDA and the USP.


Absorption spectroscopy of a compound in the UV-Vis spectral region (roughly 200-800 nm λ). The absorption maxima of a compound are used as a measure of chemical identity.

Vapor Pressure

The pressure of a vapor in equilibrium with its condensed phases.


The free online encyclopedia.