EC50
EC50 defines the molar concentration of an agonist that produces 50% of the maximum possible response for that agonist.
ED50
ED50 defines the dose of compound that produces 50% of its maximum response or effect in vitro or in vivo.
effectiveness
The ability of a drug to elicit a defined response (i.e., size or strength of a response) under normal conditions. It reflects the efficacy of a drug in real-world situations as opposed to the controlled conditions of scientific research studies.
efficacy
Efficacy describes the way that agonists vary in the response they produce when they occupy the same number of receptors.
- High efficacy agonists produce their maximal response while occupying a relatively low proportion of the total receptor population.
- Lower efficacy agonists do not activate receptors to the same degree and may not be able to produce the maximal response.
elimination
The process by which a drug is eliminated due to biotransformation to a different molecule called a drug metabolite or excretion (i.e., removal of the drug from the body).
elimination rate constant
A value denoted by Ke (or Kel) that reflects the rate of elimination of drug per unit time in a biological system and can be calculated by dividing ln 2 (~0.693) by the half-life (t1/2) of the drug for drugs that are eliminated by first-order elimination kinetics.
Emax
Emax is the value that reflects the maximal response a drug can produce in a particular tissue. It is determined by measuring responses to several increasing concentrations of drug in a biological system.
endocrine
Pertaining to glands which secrete hormones (or other products) directly in to the blood. Endocrine factors generally take effect as sites distant from their release site.
enteral administration
Enteral administration routes include the oral, sublingual and rectal routes. Enteral administration facilitates systemic exposure to the drug.
epigenetics
The study of heritable changes in phenotype that does not involve changes in the underlying DNA sequence.
euchromatin
A loosely packed form of chromatin that is typically actively being transcribed or is accessible for transcription.
ex vivo
Taking place outside a living organism.
excretion
The removal of a drug from the body, often in urine, feces, sweat, saliva, or breast milk.
exocrine
Pertaining to glands which secrete hormones (or other products) to an epithelial surface via ducts rather than directly in to the bloodstream (cf. endocrine). Exocrine glands include the salivary and sweat glands, and glands within the gastrointestinal tract.