Below you will find a number of words and terms that may be helpful to know as you explore clinical trial participation.
​Click the words below to read their definitions. 
Adverse Event     |     ASM     |     Clinical Study    |     Double Blind Trial     |     Eligibility Criteria     |     Endpoint     
 Expanded Access     |     ​Informed Consent     |     Institutional Review Board    |     Intervention/Investigational Drug        Investigator     |     Open-label extension     |    ​Open-label study     |     Orphan drug     |     Other adverse event     
 Outcome measure   |     Patient registry  |    Pharmacokinetics    |     Phase    |     Phase 1     |    Phase 2    |     Phase 3   
  Phase 4   |     Placebo     |     ​Placebo-controlled study   |     Principal investigator (PI)  |     Protocol     |     Randomized Study     
Safety profile     |    Serious adverse event     |     Sponsor    |     Study design     |     Study IDs
Taper     |     Titration     |     U.S. Food and Drug Administration (FDA)
Adverse Event: An unfavorable change in the health of a participant, including abnormal laboratory findings, that happens during a clinical study or within a certain amount of time after the study has ended. This change may or may not be caused by the intervention/treatment being studied. (Source: ClinicalTrials.gov)
ASM: Anti-seizure medications (ASM) are a group of drugs that are extensively used, mainly for the management of epileptic seizures. 
Clinical Study: A clinical study, also known as a clinical trial, is designed to learn if an investigational drug is safe and effective for public use. Participants are given specific medical treatments and researchers closely monitor the results to help decide if the drug should be approved for wider distribution. All medications on the market today have gone through this process.
Double Blind Trial: A type of clinical trial where neither the participants nor the researchers know who is receiving the intervention and who is receiving a placebo or another control treatment.
Eligibility criteria: The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). (Source: ClinicalTrials.gov)
Endpoint: In clinical trials, an event or outcome that can be measured objectively to determine whether the intervention being studied is beneficial. The endpoints of a clinical trial are usually included in the study objectives. Some examples of endpoints are improvements in quality of life and relief of symptoms. (Cancer.gov)
Expanded access: A way for patients with serious diseases or conditions who cannot participate in a clinical trial to gain access to a medical product that has not been approved by the U.S. Food and Drug Administration (FDA). (Source: ClinicalTrials.gov)
Informed consent: A process used by researchers to communicate to potential and enrolled participants the risks and potential benefits of participating in a clinical study. (Source: ClinicalTrials.gov)
Institutional Review Board (IRB): A group that has been formally designated to review and monitor biomedical research involving human subjects. In accordance with FDA regulations, an IRB has the authority to approve, require modifications, or disapprove research. This group review serves an important role in the protection of the rights and welfare of human research subjects. (Source: FDA.gov)
Intervention/Investigational Drug: Also called an experimental drug, this is the drug being studied in the clinical trial to see if your disease or medical condition improves while taking it. In clinical trials, scientists are trying to prove: if the drug is safe and effective; how the drug might be used in that disease; how much of the drug is needed; the potential benefits and risks of taking the drug. (Source: FDA.gov)
Investigator: A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator. (Source: ClinicalTrials.gov)
Open-label extension: A phase of a clinical trial in which all participants receive the investigational treatment, usually after the initial randomized or blinded phase has ended.These extensions are often used in chronic conditions, rare diseases, or when a drug shows promising benefits during earlier trial phases.
Open-label study: A type of clinical trial where both the participants and researchers know which treatment is being given. Unlike double-blind studies, there is no placebo or hidden control group.
Orphan drug: A drug for a rare disease or condition. Some rare disease treatments have been “orphaned” or discontinued because there was not enough financial incentive to continue development or production. The Orphan Drug Act incentivizes drug development for rare diseases, and defines a rare disease as a disease or condition that affects less than 200,000 people in the United States. (Source: FDA.gov)
Other adverse event: An adverse event that is not a serious adverse event, meaning that it does not result in death, is not life-threatening, does not require inpatient hospitalization or extend a current hospital stay, does not result in an ongoing or significant incapacity or interfere substantially with normal life functions, and does not cause a congenital anomaly or birth defect; it also does not put the participant in danger and does not require medical or surgical intervention to prevent one of the results listed above. (Source: ClinicalTrials.gov)
Outcome measure: For clinical trials, a planned measurement described in the protocol that is used to determine the effect of an intervention/treatment on participants. For observational studies, a measurement or observation that is used to describe patterns of diseases or traits, or associations with exposures, risk factors, or treatment. Types of outcome measures include primary outcome measure and secondary outcome measure. (Source: ClinicalTrials.gov)
Patient registry: A type of observational study that collects information about patients' medical conditions and/or treatments to better understand how a condition or treatment affects patients in the real world. (Source: ClinicalTrials.gov)
Pharmacokinetics: The absorption, distribution, metabolism, and excretion of a drug under investigation. A pharmacokinetic (PK) blood test measures how a drug is absorbed, distributed, metabolized, and excreted from the body. PK studies involve taking blood samples over time to evaluate how a drug is used by the body.
Phase: The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions. (Source: ClinicalTrials.gov)
Phase 1: A phase of research to describe clinical trials that focus on the safety of a drug. They are usually conducted with healthy volunteers, and the goal is to determine the drug's most frequent and serious adverse events and, often, how the drug is broken down and excreted by the body. These trials usually involve a small number of participants.(Source: ClinicalTrials.gov)
Phase 2: A phase of research to describe clinical trials that gather preliminary data on whether a drug works in people who have a certain condition/disease (that is, the drug's effectiveness). For example, participants receiving the drug may be compared to similar participants receiving a different treatment, usually an inactive substance (called a placebo) or a different drug. Safety continues to be evaluated, and short-term adverse events are studied.(Source: ClinicalTrials.gov)
Phase 3: A phase of research to describe clinical trials that gather more information about a drug's safety and effectiveness by studying different populations and different dosages and by using the drug in combination with other drugs. These studies typically involve more participants. (Source: ClinicalTrials.gov)
Phase 4: A phase of research to describe clinical trials occurring after FDA has approved a drug for marketing. They include postmarket requirement and commitment studies that are required of or agreed to by the study sponsor. These trials gather additional information about a drug's safety, efficacy, or optimal use. (Source: ClinicalTrials.gov)
Placebo: An inactive substance that looks the same as, and is given in the same way as, an intervention/treatment being studied (Source: ClinicalTrials.gov)
Placebo-controlled study: ​A type of clinical trial where participants are divided into groups, with one group receiving the actual treatment and another receiving a placebo—a substance that looks like the treatment but has no active ingredients.
Principal investigator (PI): The person who is responsible for the scientific and technical direction of the entire clinical study. (Source: ClinicalTrials.gov)
Protocol: The written description of a clinical study. It includes the study's objectives, design, and methods. It may also include relevant scientific background and statistical information. (Source: ClinicalTrials.gov)
Randomized Study: ​A randomized controlled study is a type of study that aims to reduce bias when testing a new treatment. The people participating in the study are randomly allocated to either the group receiving the treatment under investigation or to a group receiving standard treatment as the control.
Safety profile: The overall assessment of an intervention’s safety, based on data collected from clinical trials. It includes information on adverse events (AEs), serious adverse events (SAEs), dose-related toxicity, and long-term safety risks. An intervention’s safety profile continues to be monitored even after market approval.
Serious​ adverse event: An adverse event that results in death, is life-threatening, requires inpatient hospitalization or extends a current hospital stay, results in an ongoing or significant incapacity or interferes substantially with normal life functions, or causes a congenital anomaly or birth defect. Medical events that do not result in death, are not life-threatening, or do not require hospitalization may be considered serious adverse events if they put the participant in danger or require medical or surgical intervention to prevent one of the results listed above. (Source: ClinicalTrials.gov)
Sponsor: The organization or person who initiates the study and who has authority and control over the study. (Source: ClinicalTrials.gov)
Study design: The investigative methods and strategies used in the clinical study.  (Source: ClinicalTrials.gov)
Study IDs: Identifiers that are assigned to a clinical study by the study's sponsor, funders, or others. They include unique identifiers from other trial study registries and National Institutes of Health grant numbers. Note: ClinicalTrials.gov assigns a unique identification code to each clinical study registered on ClinicalTrials.gov. Also called the NCT number, the format is "NCT" followed by an 8-digit number (for example, NCT00000419).  (Source: ClinicalTrials.gov)
Taper:​ In medicine, tapering is the practice of gradually reducing the dosage of a medication to reduce or discontinue it.
Titration: Titration is a way to limit potential side effects by taking time to see how your body will react to a drug.
U.S. Food and Drug Administration (FDA): An agency within the U.S. Department of Health and Human Services. The FDA is responsible for protecting the public health by making sure that human and veterinary drugs, vaccines and other biological products, medical devices, the Nation's food supply, cosmetics, dietary supplements, and products that give off radiation are safe, effective, and secure. (Source: ClinicalTrials.gov)