Terminology Associated with Clinical Trials

Terminology Associated with Clinical Trials

Adverse Drug Reaction (ADR)

An unintended reaction to a drug taken at doses normally used in man for prophylaxis, diagnosis, or therapy of disease, or for the modification of physiological function. In clinical trials, an ADR would include any injuries by overdosing, abuse/dependence, and unintended interactions with other medicinal products.

Adverse Event (AE)

A negative experience encountered by an individual during the course of a clinical trial, that is associated with the drug. An AE can include previously undetected symptoms, or the exacerbation of a pre-existing condition. When an AE has been determined to be related to the investigational product, it is considered an Adverse Drug Reaction.

Approved Drugs

In the U.S., the Food and Drug Administration (FDA) must approve a substance as a drug before it can be marketed. The approval process involves several steps including pre-clinical laboratory and animal studies, clinical trials for safety and efficacy, filing of a New Drug Application by the manufacturer of the drug, FDA review of the application, and FDA approval/rejection of application.


Refers to any treatment groups in a trial. Most randomized trials have two “arms,” but some have three “arms,” or even more.


Information gathered at the beginning of a study from which variations found in the study are measured.


When a point of view prevents impartial judgment on issues relating to the subject of that point of view. In clinical studies, bias is controlled by blinding and randomization.


A virus, therapeutic serum, toxin, antitoxin, vaccine, blood, blood component or derivative, allergenic product, or analogous product applicable to the prevention, treatment or cure of diseases or injuries of man.


The process through which one or more parties to a clinical trial are unaware of the treatment assignments. In a single-blinded study, usually the subjects are unaware of the treatment assignments. In a double-blinded study, both the subjects and the investigators are unaware of the treatment assignments. Also, in a double-blinded study, the monitors and sometimes the data analysts are unaware. “Blinded” studies are conducted to prevent the unintentional biases that can affect subject data when treatment assignments are known.

Clinical Development

Term used to describe the cross-functional and cross-departmental activities that are required to bring an investigational product from Phase I through Phase IV.

Clinical Investigation

A systematic study designed to evaluate a product (drug, device, or biologic) using human subjects, in the treatment, prevention, or diagnosis of a disease or condition, as determined by the product’s benefits relative to its risks. Clinical investigations can only be conducted with the approval of the Food and Drug Administration (FDA).

Clinical Investigator

A medical researcher in charge of carrying out a clinical trial’s protocol.

Clinical Trial

Any investigation in human subjects intended to determine the clinical pharmacological, pharmacokinetic, and/or other pharmacodynamic effects of an investigational agent, and/or to identify any adverse reactions to an investigational agent to assess the agent’s safety and efficacy. Phases of clinical trials are described here (link to PDF on IRD tool kit)

Comparator (Product)

An investigational or marketed product (i.e., active control), or placebo, used as a reference in a clinical trial.

Consent Form

A document explaining all relevant study information to assist the study volunteer in understanding the expectations and requirements of participation in a clinical trial. This document is presented to and signed by the study subject.


A specific circumstance when the use of certain treatments could be harmful.

Control Group

A comparison group of study subjects who are not treated with the investigational agent. The subjects in this group may receive no therapy, a different therapy, or a placebo.

Demographic Data

Refers to the characteristics of study participants, including sex, age, family medical history, and other characteristics relevant to the study in which they are enrolled.


An instrument, apparatus, implant, including any component, part or accessory, which is intended for use in the diagnosis, cure, treatment or prevention of disease. A device does not achieve its intended purpose through chemical action in the body and is not dependent upon being metabolized to achieve its purpose.

Diagnostic Trials

Refers to trials that are conducted to find better tests or procedures for diagnosing a particular disease or condition. Diagnostic trials usually include people who have signs or symptoms of the disease or condition being studied.

Dosage Regimen

The number of doses per given time period, the time that elapses between doses, or the time that the doses are to be given, or the quantity of a medicine that are given at each specific time of dosing.

Dose-Ranging Study

A clinical trial in which two or more doses of an agent (such as a drug) are tested against each other to determine which dose works best and is least harmful.

Drug Safety and Monitoring Board (DSMB)

An independent committee, composed of community representatives and clinical research experts, that reviews data while a clinical trial is in progress to ensure that participants are not exposed to undue risk. A DSMB may recommend that a trial be stopped if there are safety concerns or if the trial objectives have been achieved.

Drug-Drug Interaction

A modification of the effect of a drug when administered with another drug. The effect may be an increase or a decrease in the action of either substance, or it may be an adverse effect that is not normally associated with either drug.

Effective Concentration or Dose

The concentration or dose of a product that produces a beneficial effect on the duration or course of a disease. 


A product’s ability to produce beneficial effects on the duration or course of a disease.


Field relating to hormone-manufacturing glands such as the pituitary, thyroid, parathyroid, and adrenal glands, as well as the ovary and testis, the placenta, and the pancreas. Studies in this area include: diabetes and diabetes-related disorders, diet and nutrition, hormone-replacement therapy, menopause, obesity, and others.


Overall outcome that the protocol is designed to evaluate. 


The act of signing up participants into a study. Generally, this process involves evaluating a participant with respect to the eligibility criteria of the study and going through the informed consent process.

Exclusion Criteria

Refers to the characteristics that would prevent a subject from participating in a clinical trial, as outlined in the study protocol.

Expanded Access

Indicates that the treatment (drug, biologic or medical device) is accessible to patients who were not on the clinical trial.

Experimental Drug

A drug that is not FDA licensed for use in humans, or as a treatment for a particular condition.

Generic Drug

A medicinal product with the same active ingredient, but not necessarily the same inactive ingredients as a brand-name drug. A generic drug may only be marketed after the original drug’s patent has expired.

In Vitro Testing

Non-clinical testing conducted in an artificial environment such as a test tube or culture medium.

In Vivo Testing

Testing conducted in living animal and human systems.

Incident Rate

The rate of occurrence of new cases of a disease, adverse reaction, or other event in a given population at risk.

Inclusion Criteria

A list of criteria that must be met by all study subjects.

Informed Consent

The voluntary verification of a patient’s willingness to participate in a clinical trial, along with the documentation thereof. This verification is requested only after complete, objective information has been given about the trial, including an explanation of the study’s objectives, potential benefits, risks and inconveniences, alternative therapies available, and of the subject’s rights and responsibilities in accordance with the current revision of the Declaration of Helsinki.

Longitudinal Study

A study conducted over a long period of time.


Reviewing a clinical study, ensuring conduct, proper records and reports are performed as stated in the clinical protocol, standard operating procedures, Good Clinical Practice and by regulatory requirements.

Natural History Study

Study of the natural development of something a disease over a period of time.

New Drug Application (NDA)

The compilation of all non-clinical, clinical, pharmacological, pharmacokinetic and stability information required about a drug by the FDA in order to approve the drug for marketing in the U.S.

Off Label

The unauthorized use of a drug for a purpose other than that approved of by the FDA.

Open-Label Study

A study in which all parties, (patient, physician and study coordinator) are informed of the drug and dose being administered. In an open-label study, none of the participants are given placebos. These are usually conducted with Phase I & II studies.

Orphan Drug

A designation of the FDA to indicate a therapy developed to treat a rare disease. Because there are few financial incentives for drug companies to develop therapies for diseases that afflict so few people, the U.S. government offers additional incentives to drug companies (i.e. tax advantages and extended marketing exclusivity) that develop these drugs.

Peer Review

Review of a clinical trial by experts chosen by the study sponsor. These experts review the trials for scientific merit, participant safety, and ethical considerations.

Pharmaco-dynamic (PD) Study

A study of a pharmacological or clinical effect of the medicine in individuals to describe the relation of the effect to dose or drug concentration. A pharmacodynamic effect can be a potentially adverse effect, a measure of activity thought to be related to clinical benefit, a short term desired effect, often a surrogate endpoint, or the ultimate intended clinical benefit.


The study of cost-benefit ratios of drugs with other therapies or with similar drugs. Pharmaco-economic studies compare various treatment options in terms of their cost, both financial and quality-of-life. Also referred to as “outcomes research”.


The movement of a drug through the body by the processes (in a living organism) of absorption, distribution, metabolism, and excretion of a drug or vaccine.


The science of drugs and poisonous materials (respectively) and their effects on the body.

Placebo Effect

A physical or emotional change, occurring after a substance is taken or administered, that is not the result of any special property of the substance. The change may be beneficial, reflecting the expectations of the participant and, often, the expectations of the person giving the substance.

Pre-Clinical Testing

Before a drug may be tested on humans, pre-clinical studies must be conducted either in vitro (test tube) but usually in vivo on animals to determine that the drug is safe.


A detailed plan that sets forth the objectives, study design, and methodology for a clinical trial. A study protocol must be approved before investigational drugs may be administered to humans.

Quality of Life Trials (or Supportive Care Trials)

Refers to trials that explore ways to improve comfort and quality of life for individuals with a chronic illness.


Study participants are usually assigned to groups in such a way that each participant has an equal chance of being assigned to each treatment (or control) group. Since randomization ensures that no specific criteria are used to assign any patients to a particular group, all the groups will be equally comparable.


Act of enrolling subjects with the proper inclusion criteria.

Recruitment Period

Time allowed to recruit all subjects for a study.

Risk-Benefit Ratio

Risk to individual subject vs. potential benefits. Also called Risk-Benefit Analysis.

Side Effects

Any undesired actions or effects of a drug or treatment. Experimental drugs must be evaluated for both immediate and long-term side effects.

Standard Operating Procedure (SOP)

Official, detailed, written instructions for the management of clinical trials. SOPs ensure that all the functions and activities of a clinical trial are carried out in a consistent and efficient manner.

Standard Treatment

The currently accepted treatment or intervention considered to be effective in the treatment of a specific disease or condition.

Standards of Care

Treatment regimen or medical management based on state of the art participant care.

Statistical Significance

The probability that an event or difference did not occur by chance alone. In clinical trials, the level of statistical significance depends on the number of participants studied and the observations made, as well as the magnitude of differences observed.

Study Endpoint

A primary or secondary outcome used to judge the effectiveness of a treatment.

Therapeutic Window

This term is applied to the difference between the minimum and maximum doses that may be given subjects to obtain an adequate clinical response and avoid intolerable toxic effects. The greater the value calculated for the therapeutic window, the greater a medicine’s margin of safety. Synonyms are therapeutic ratio and therapeutic index.


An adverse effect produced by a drug that is detrimental to the participant’s health. The level of toxicity associated with a drug will vary depending on the condition which the drug is used to treat.

Treatment Trials

Refers to trials which test new treatments, new combinations of drugs, or new approaches to surgery or radiation therapy.

Unexpected Adverse Drug Reaction

A reaction that is not consistent in nature or severity with study application.

Vulnerable Subjects

Group/individual that cannot give informed consent because of limited autonomy (e.g., children, mentally ill and prisoners). Also refers to subjects who may be unduly influenced to participate (e.g., students, subordinates and patients).