Glossary of peptide and regulation terms

5 A B C D F G H I L M N O P R S T U W

503A bulks list (also: 503A bulks lists): The list in federal rules (21 CFR 216.23) of bulk drug substances that a 503A pharmacy may use under section 503A(b)(1)(A)(i)(III). That clause covers substances with no USP or NF monograph that are not part of an FDA-approved drug. Source: eCFR: 21 CFR 216.23, bulk drug substances for 503A compounding
503A pharmacy (also: 503A, section 503A, 503A pharmacies, 503A compounding pharmacy, 503A compounding): A state-licensed pharmacy, federal facility or physician that compounds drugs under section 503A of the FD&C Act. State boards of pharmacy do most of the day-to-day oversight of these pharmacies. Source: FDA: Compounding and the FDA, questions and answers
503B bulks list (also: 503B clinical need list, clinical need list, 503B bulk drug substances list): FDA's list of bulk drug substances for which there is a clinical need under section 503B. An outsourcing facility may compound from a bulk substance only if it is on this list or the drug is on FDA's drug shortage list. Source: FDA: Bulk drug substances used in compounding under section 503B
503B outsourcing facility (also: 503B, section 503B, outsourcing facility, outsourcing facilities, 503B outsourcing facilities): A compounder that makes sterile drugs at one location, has registered with FDA as an outsourcing facility, and meets all the rules in section 503B of the FD&C Act. This category was created by the Drug Quality and Security Act, signed on November 27, 2013. Source: FDA: Information for outsourcing facilities
A1C (also: A1c, HbA1c, hemoglobin A1C, HbA1C): A blood test that shows a person's average blood sugar over the past two to three months. Source: MedlinePlus (NLM): Hemoglobin A1C (HbA1c) test
Abbreviated New Drug Application (also: ANDA, ANDAs): The application a company files to get FDA approval for a generic drug. It shows the generic matches the brand-name drug it copies in dosage form, strength, route and quality. Source: FDA: Abbreviated New Drug Application (ANDA)
Active ingredient (also: active ingredients): The part of a drug that is meant to have a drug effect on the body. Other parts, such as fillers or liquids, are inactive ingredients. Source: eCFR: 21 CFR 210.3, definitions
Adverse event (also: adverse events, adverse event report, adverse event reports, adverse effect, adverse effects, adverse reaction, adverse reactions): An unwanted effect of a drug or other treatment. Adverse events can be mild, severe or life-threatening. Also called an adverse effect or adverse reaction. Source: NIH National Cancer Institute: adverse event (Dictionary of Cancer Terms)
Agonist (also: agonists): A drug or substance that binds to a receptor and triggers the same action as the body's own substance that normally binds there. Source: NIH National Cancer Institute: agonist (Dictionary of Cancer Terms)
Albumin: A type of protein found in blood, egg white, milk and other substances. Some peptide drugs are designed to bind albumin in the blood. Source: NIH National Cancer Institute: albumin (Dictionary of Cancer Terms)
Alpha-MSH (also: alpha-melanocyte stimulating hormone, alpha-melanocyte-stimulating hormone, α-MSH): Alpha-melanocyte stimulating hormone, a natural 13 amino acid peptide hormone made from the POMC gene. It helps control the making of melanin, the pigment in skin. Source: NCI Thesaurus (NIH): Melanotropin alpha, C114797
Amino acid (also: amino acids): A small molecule that links with others to form peptides and proteins. Peptide length is counted in amino acids. Source: MedlinePlus (NLM): Amino acids
Amylin (also: amylin analog, amylin analogs): A natural hormone made by the beta cells of the pancreas that helps control blood sugar after meals. Pramlintide (Symlin) is an FDA-approved lab-made analog of amylin. Source: DailyMed: Symlin (pramlintide acetate) label
Analog (also: analogs): A substance that is similar, but not identical, to another. Many peptide drugs are analogs of natural hormones, changed to last longer or bind more strongly. Source: NIH National Cancer Institute: analog (Dictionary of Cancer Terms)
Antimicrobial peptide (also: antimicrobial peptides, host defense peptide, host defense peptides): A natural or lab-made peptide that kills or slows the growth of germs such as bacteria. Some also affect the immune system. LL-37 is a human example. Source: NCI Thesaurus (NIH): Antimicrobial Peptide, C123795
Biologic (also: biologics, biological product, biological products): A biological product, often a protein, that FDA licenses through a Biologics License Application. FDA says biologics are not eligible for the 503A and 503B compounding exemptions. Source: FDA: Compounding and the FDA, questions and answers
Biologics License Application (also: BLA, BLAs): The formal request a company files to get FDA approval to market a biological product in the United States. It must show the product is safe and effective and can be made to consistent quality. Source: FDA: Biologics License Applications (BLA)
Boxed warning (also: boxed warnings, black box warning, black box warnings): A warning FDA can require in a box at the top of a prescription drug label, under a heading that includes the word WARNING. It is used for serious risks, especially ones that may lead to death or serious injury. Source: eCFR: 21 CFR 201.57, prescription drug labeling content
Bulk drug substance (also: bulk drug substances, bulk substance, bulk substances, active pharmaceutical ingredient, bulk powder): The raw active ingredient a compounder starts from. Federal rules say it means the same as active pharmaceutical ingredient. Source: eCFR: 21 CFR 207.3, bulk drug substance
Case report (also: case reports, case series): A detailed report of the diagnosis, treatment and follow-up of one patient. Because it describes a single person, it cannot show how often an effect happens. Source: NIH National Cancer Institute: case report (Dictionary of Cancer Terms)
Category 1 (also: category 1 substances, 503A category 1, 503B category 1): An FDA interim category for nominated bulk drug substances that had enough supporting information for FDA to review them and are not on another FDA list. FDA does not intend to act against compounders using Category 1 substances while it reviews them, if the policy's conditions are met. Source: FDA: Bulk drug substances used in compounding under section 503A
Category 2 (also: category 2 substances, 503A category 2, 503B category 2): An FDA interim category for nominated bulk drug substances where FDA has found significant safety risks. The interim policy does not cover them, so compounders may face FDA action for using them while FDA reviews them. Source: FDA: Bulk drug substances used in compounding under section 503A
Category 3 (also: category 3 substances, 503A category 3): An FDA interim category for bulk drug substances that were nominated without enough supporting information for FDA to review them. They can be nominated again with more information. Source: FDA: Bulk drug substances used in compounding under section 503A
Cathelicidin (also: cathelicidins, human cathelicidin): A family of antimicrobial peptides. LL-37 is the 37 amino acid human member of this family. Source: NCI Thesaurus (NIH): Ropocamptide (synthetic LL-37), C118292
Cell culture (also: cell cultures, cultured cells): Growing cells in a lab dish. Cell culture results show what a substance does to cells, not what it does in a whole person. Source: NIH National Cancer Institute: cell culture (Dictionary of Cancer Terms)
CGMP (also: current good manufacturing practice, current good manufacturing practices): Current good manufacturing practice: FDA's minimum rules for the methods, facilities and controls used to make, process and pack drugs. They help make sure a drug has the ingredients and strength it claims. Source: FDA: Current Good Manufacturing Practice (CGMP) regulations
Clinical trial (also: clinical trials, clinical study, clinical studies): A research study that tests a medical approach in people. Trials test new ways to screen for, prevent, diagnose or treat a disease. Source: NIH National Cancer Institute: clinical trial (Dictionary of Cancer Terms)
ClinicalTrials.gov: A searchable registry and results database of publicly and privately supported clinical trials in the United States and around the world. It shows each trial's purpose, who may take part and where. Source: NIH: Finding a clinical trial
Comment period (also: comment periods, public comment): The window after an agency notice or proposed rule is published in the Federal Register when anyone may send written comments. Agencies can extend it. For example, FDA extended a 503B bulks list comment period to July 30, 2026. Source: Federal Register: 503B bulks list notice, extension of comment period (Jun 26, 2026)
Compounding (also: compounded, compounded drug, compounded drugs, drug compounding, compounder, compounders): When a licensed pharmacist or physician, or a supervised person at an outsourcing facility, combines, mixes or changes drug ingredients to make a medicine for a patient's needs. Compounded drugs are not FDA approved. FDA does not review their safety, effectiveness or quality before they are sold. Source: FDA: Human drug compounding
Controlled substance (also: controlled substances, DEA schedule, schedule II to V, Schedule I): A drug the DEA places in one of five schedules based on its accepted medical use, abuse potential and risk of dependence. Schedule I drugs have no accepted medical use in the United States. Source: DEA Diversion Control Division: Controlled substance schedules
Crossover trial (also: crossover, crossover study, crossover studies): A trial in which every participant gets each treatment, such as the drug and a placebo, in a random order. There is usually a rest period between them. Source: NIH National Cancer Institute: crossover study (Dictionary of Cancer Terms)
DAC (also: drug affinity complex): Drug affinity complex, a chemical add-on to CJC-1295 that lets it bind albumin in the blood. FDA notes this binding to albumin is what makes the DAC form more stable than the form without DAC. Source: FDA: PCAC briefing document, CJC-1295-related bulk drug substances, December 4, 2024
DailyMed: A National Library of Medicine database of drug labels that companies submit to FDA. It holds the prescribing information and patient labeling for FDA-approved drugs. Source: DailyMed (NLM): About DailyMed
DEA (also: Drug Enforcement Administration): The Drug Enforcement Administration, the federal agency in charge of controlled substances. It places drugs into schedules and registers those who handle them. Source: DEA Diversion Control Division: Controlled substance schedules
Docket (also: dockets, public docket, docket number): A public file of documents for an agency action, such as a proposed rule or list change. It holds the Federal Register notices, the public comments and other material the agency relies on. Each docket has an ID, such as FDA-2018-N-3240. Source: EPA: About dockets
Double-blind (also: double-blinded, double blind, double-blind study): A trial design in which neither the participants nor the researchers know who is getting which treatment until the trial ends. This makes the results less likely to be biased. Source: NIH National Cancer Institute: double-blind study (Dictionary of Cancer Terms)
Drug label (also: FDA label, FDA labels, drug labels, prescribing information, FDA-approved label): The FDA-approved prescribing information and patient labeling for a drug. Labels for approved drugs are posted on DailyMed. Source: DailyMed (NLM): About DailyMed
Drug Quality and Security Act (also: DQSA): A federal law enacted on November 27, 2013, after a 2012 fungal meningitis outbreak tied to compounded drugs. It confirmed section 503A and added section 503B, which created outsourcing facilities. Source: FDA: Human drug compounding laws
Drug shortage list (also: shortage list, FDA shortage list, drug shortage, drug shortages, Drug Shortages database, Drug Shortage Database): FDA's public list of drugs in shortage. An outsourcing facility may compound from a bulk substance that is not on the 503B bulks list only if the drug is on this list at the time of compounding. Source: FDA: Bulk drug substances used in compounding under section 503B
Drugs@FDA: FDA's public database of approved drugs. It covers most drugs approved since 1939 and has labels, approval letters and reviews for most drugs approved since 1998. Source: FDA: About Drugs@FDA
FAERS (also: FDA Adverse Event Reporting System, AEMS, FDA Adverse Event Monitoring System): FDA's database of adverse event reports, medication error reports and product quality complaints sent to FDA. FDA now also lists it under the name Adverse Event Monitoring System (AEMS). Source: FDA: Adverse Event Reporting System (FAERS)
FDA approval (also: FDA-approved, FDA approved, approved drug, approved drugs): FDA's decision, after reviewing a company's data, that a drug's benefits outweigh its known and possible risks for the people it is meant for. Approval covers specific uses, doses and forms listed on the label. Source: FDA: Development and approval process (drugs)
Federal Food, Drug, and Cosmetic Act (also: FD&C Act, FDCA): The federal law that sets FDA's rules for drugs, including approval before sale. Sections 503A and 503B of this law set the rules for compounding. Source: FDA: Human drug compounding laws
Federal Register (also: Federal Register notice, Federal Register notices): The daily journal of the U.S. government. Agencies publish rules, proposed rules and notices in it, including FDA changes to compounding lists. Source: National Archives: About the Federal Register
Generic drug (also: generic drugs, generic, generics): An FDA-approved copy of a brand-name drug. It must be the same in dosage, safety, effectiveness, strength, quality and the way it is taken. Source: FDA: Generic drug facts
Ghrelin (also: ghrelin receptor, ghrelin receptors, ghrelin receptor agonist): A natural hormone involved in hunger and in controlling growth hormone release. Source: NCI Thesaurus (NIH): Appetite-regulating hormone (ghrelin), C104429
GHRH (also: growth hormone-releasing hormone, growth hormone releasing hormone, GHRH analog, GHRH analogs, growth hormone-releasing factor): Growth hormone-releasing hormone, a natural hormone that causes the pituitary gland to release growth hormone. Source: NCI Thesaurus (NIH): Somatoliberin (GHRH), C28419
GHRP (also: GHRPs, growth hormone-releasing peptide, growth hormone-releasing peptides, GH-releasing peptides): Growth hormone-releasing peptides, a group of lab-made peptides such as GHRP-2 and GHRP-6. FDA notes their structure decides how they bind ghrelin receptors. Source: FDA: PCAC briefing document, ipamorelin-related bulk drug substances, October 29, 2024
GIP (also: glucose-dependent insulinotropic polypeptide, GIP receptor): Glucose-dependent insulinotropic polypeptide, a hormone released from the gut after eating. Tirzepatide acts on both GIP and GLP-1 receptors. Source: FDA: FDA approves new medication for chronic weight management (Nov 8, 2023)
GLP-1 (also: glucagon-like peptide-1, glucagon-like peptide 1, GLP-1 receptor): Glucagon-like peptide-1, a natural 37 amino acid hormone made in the gut. It helps trigger insulin release when blood sugar rises. Source: NCI Thesaurus (NIH): Glucagon-Like Peptide 1, C190208
GLP-1 receptor agonist (also: GLP-1 receptor agonists, GLP-1 drugs, GLP-1 drug, GLP-1 analog): A drug that binds and activates the GLP-1 receptor, the same target as the body's own GLP-1. Semaglutide is an example. Source: DailyMed: Ozempic (semaglutide) injection label
Glucagon (also: glucagon receptor): A hormone made by the pancreas that raises blood sugar. Source: NIH National Cancer Institute: glucagon (Dictionary of Cancer Terms)
Growth hormone (also: GH, human growth hormone, somatotropin): A protein hormone made by the pituitary gland. It helps control body growth and how the body uses sugar and fat. Source: NIH National Cancer Institute: growth hormone (Dictionary of Cancer Terms)
Growth hormone secretagogue (also: growth hormone secretagogues, GHS, GH secretagogue, secretagogue, secretagogues): A substance that causes the body to release its own growth hormone. FDA describes this class as peptide or non-peptide agents, such as ipamorelin, that act on ghrelin receptors. Source: FDA: PCAC briefing document, ipamorelin-related bulk drug substances, October 29, 2024
Half-life (also: half-lives, half life): The time it takes for a substance to lose half of its activity. For a drug, it gives a sense of how long the drug stays active in the body. Source: NCI Thesaurus (NIH): Half Life, C70916
Healthy volunteers (also: healthy volunteer, healthy adults): People without the condition being studied who take part in research. Studies with healthy volunteers aim to build knowledge, not to give them a direct benefit. Source: NIH: The basics of clinical trials
HSDD (also: hypoactive sexual desire disorder): Hypoactive sexual desire disorder, low sexual desire that causes marked distress or relationship difficulty and is not due to another condition, a relationship problem or a drug. Vyleesi is approved for acquired, generalized HSDD in premenopausal women. Source: DailyMed: Vyleesi (bremelanotide injection) label
IGF-1 (also: insulin-like growth factor 1, insulin-like growth factor-1, insulin-like growth factor I): Insulin-like growth factor 1, a protein made by the body that stimulates the growth of many types of cells. It is one of two forms of IGF. Source: NIH National Cancer Institute: IGF (Dictionary of Cancer Terms)
Import alert (also: import alerts): An FDA notice that lets border staff hold shipments of a product without testing it, because of past violations. The importer must show the product does not have the listed problem. Source: FDA: Import alerts
In vitro: In the laboratory, outside the body. The opposite of in vivo. Source: NIH National Cancer Institute: in vitro (Dictionary of Cancer Terms)
In vivo: In the body, such as in a living animal or person. The opposite of in vitro. Source: NIH National Cancer Institute: in vivo (Dictionary of Cancer Terms)
Intended use (also: intended uses): What the people responsible for a product mean it to be used for. FDA judges this from the labeling, ads, websites, statements and other evidence. Source: eCFR: 21 CFR 201.128, meaning of intended uses
Interim policy (also: interim policies): FDA's policy on bulk drug substances it has not yet decided on. It sets the conditions under which FDA does not intend to act against compounders who use them, and sorts nominated substances into Categories 1, 2 and 3. Source: FDA: Bulk drug substances used in compounding under section 503A
Intramuscular (also: intramuscularly): Into a muscle. A route used to give some drugs by injection. Source: NIH National Cancer Institute: intramuscular (Dictionary of Cancer Terms)
Intranasal (also: nasal spray, nasal sprays, nasal route): Given through the nose, such as by nasal spray. The drug can pass into the blood through the lining of the nose. Source: NCI Thesaurus (NIH): Nasal Route of Administration, C38284
Intraperitoneal (also: IP injection): Into the peritoneal cavity, the space in the belly that holds the abdominal organs. Source: NIH National Cancer Institute: intraperitoneal (Dictionary of Cancer Terms)
Intravenous (also: IV, intravenously, IV infusion): Into a vein, through a needle or tube. Source: NIH National Cancer Institute: intravenous (Dictionary of Cancer Terms)
Investigational drug (also: investigational drugs, investigational): A substance that FDA has allowed to be tested in people but has not approved for the use being studied. Source: NIH National Cancer Institute: investigational drug (Dictionary of Cancer Terms)
Lipodystrophy: A condition with abnormal loss or shifting of body fat. It can be inherited or acquired. Source: NCI Thesaurus (NIH): Lipodystrophy, C97093
MASH (also: metabolic dysfunction-associated steatohepatitis, NASH, nonalcoholic steatohepatitis): Metabolic dysfunction-associated steatohepatitis, a liver disease with fat in the liver plus inflammation and liver damage. It is also called NASH. Source: NIH NIDDK: Definition and facts of NAFLD and NASH
Medullary thyroid cancer (also: medullary thyroid carcinoma, MTC): A cancer that starts in the C cells of the thyroid. These cells make calcitonin, a hormone that helps keep blood calcium normal. Source: NIH National Cancer Institute: medullary thyroid cancer (Dictionary of Cancer Terms)
MedWatch: FDA's safety information and adverse event reporting program. Patients and health professionals can use it to report serious problems with drugs and other medical products. Source: FDA: MedWatch, safety information and adverse event reporting program
Melanocortin receptor (also: melanocortin receptors, melanocortin receptor agonist, melanocortin): A type of receptor targeted by bremelanotide. Its FDA label calls Vyleesi a melanocortin receptor agonist. Source: DailyMed: Vyleesi (bremelanotide injection) label
Melanoma: A cancer that starts in melanocytes, the cells that make skin pigment. It often begins in a mole. Source: NIH National Cancer Institute: melanoma (Dictionary of Cancer Terms)
MEN 2 (also: MEN2, multiple endocrine neoplasia type 2): Multiple endocrine neoplasia type 2, a rare inherited condition that causes tumors in hormone glands. Its most common sign is medullary thyroid cancer. Source: MedlinePlus Genetics (NLM): Multiple endocrine neoplasia
Monitoring Program (also: WADA Monitoring Program, 2026 Monitoring Program): A WADA list of substances that are not banned but that WADA tracks to spot possible misuse in sport. Markers of semaglutide and tirzepatide are on the 2026 Monitoring Program. Source: WADA: 2026 Monitoring Program (PDF)
New Drug Application (also: NDA, NDAs): The application a drug company files asking FDA to approve a new drug for sale in the United States. It includes the data from animal studies and human trials. Source: FDA: New Drug Application (NDA)
Obesity: A common, chronic disease with an unhealthy amount of body fat. It raises the risk of heart disease, diabetes, sleep apnea and other problems. Source: NIH National Cancer Institute: obesity (Dictionary of Cancer Terms)
Obstructive sleep apnea (also: OSA, sleep apnea): A sleep condition in which the upper airway gets blocked many times during sleep, so breathing stops and restarts. It is the most common type of sleep apnea. Source: NIH NHLBI: What is sleep apnea?
Off-label use (also: off-label, off label): Using an FDA-approved drug for a use that is not on its label. FDA says providers generally may do this when they judge it medically appropriate for the patient. Source: FDA: Understanding unapproved use of approved drugs off label
Office Use Only (also: office use): A label statement required on drugs from a 503B outsourcing facility that are given out without a prescription for a named patient, for example to a clinic. Source: 21 U.S.C. 353b (FD&C Act section 503B), U.S. Code (govinfo)
Open-label (also: open label, open-label study, open-label extension, nonblinded): A study in which both the researchers and the participants know which drug or treatment is being given. Source: NIH National Cancer Institute: open label study (Dictionary of Cancer Terms)
Orphan drug designation (also: orphan designation, orphan drug, orphan drugs): A status for a drug for a rare disease, one that affects fewer than 200,000 people in the United States. The Orphan Drug Act of 1983 gives companies benefits for developing these drugs. Source: NIH National Cancer Institute: orphan drug (Dictionary of Cancer Terms)
Pancreatitis: Inflammation of the pancreas. Pain is the main symptom. Source: NIH National Cancer Institute: pancreatitis (Dictionary of Cancer Terms)
Patient-specific prescription (also: patient-specific, patient-specific prescriptions): A valid prescription written for one named patient. Under section 503A, a pharmacy compounds based on these prescriptions, plus limited amounts made ahead based on past orders. Source: 21 U.S.C. 353a (FD&C Act section 503A), U.S. Code (govinfo)
Peptide (also: peptides): A short chain of amino acids, typically 2 to 50, linked by peptide bonds. Longer chains are called polypeptides, and proteins are made of one or more polypeptides. Source: NIH National Human Genome Research Institute: Peptide (glossary)
Pharmacokinetics (also: pharmacokinetic): How a drug moves through the body over time: how it is absorbed, spread through the body, held in tissues and removed. Source: NIH National Cancer Institute: pharmacokinetics (Dictionary of Cancer Terms)
Pharmacy Compounding Advisory Committee (also: PCAC): An FDA committee of outside experts that advises FDA on scientific, technical and medical issues in compounding under sections 503A and 503B. It makes recommendations, and FDA decides. Source: FDA: Pharmacy Compounding Advisory Committee
Phase 1 trial (also: phase 1, phase I, phase 1 study, phase 1 trials): The first step in testing a new drug in people. It enrolls 20 to 100 healthy volunteers or people with the condition, and its purpose is safety and dosage. Source: FDA: Step 3, clinical research
Phase 2 trial (also: phase 2, phase II, phase 2 study, phase 2 trials): A trial in up to several hundred people with the condition. Its purpose is to look at efficacy and side effects. Source: FDA: Step 3, clinical research
Phase 3 trial (also: phase 3, phase III, phase 3 study, phase 3 trials): A large trial in 300 to 3,000 people with the condition. Its purpose is to test efficacy and watch for adverse reactions. Source: FDA: Step 3, clinical research
Pineal gland (also: pineal): A tiny organ in the brain that makes melatonin. Source: NIH National Cancer Institute: pineal gland (Dictionary of Cancer Terms)
Pituitary gland (also: pituitary): A pea-sized organ at the base of the brain. It makes hormones, including growth hormone, that control other glands and functions such as growth and fertility. Source: NIH National Cancer Institute: pituitary gland (Dictionary of Cancer Terms)
Placebo (also: placebos, placebo-controlled, placebo group): An inactive substance that looks the same as, and is given the same way as, the drug being tested. Comparing the two groups shows the drug's own effect. Source: NIH National Cancer Institute: placebo (Dictionary of Cancer Terms)
Preclinical research (also: preclinical, preclinical study, preclinical studies, animal studies, animal study): Lab (in vitro) and animal (in vivo) research done before a drug is tested in people. It checks whether the drug may cause serious harm. Source: FDA: Step 2, preclinical research
Priapism: An erection that lasts four hours or more without sexual stimulation, often painful. Medicines are one known cause. Source: NCI Thesaurus (NIH): Priapism, C85022
Prohibited List (also: WADA Prohibited List, 2026 Prohibited List, 2027 Prohibited List, List of Prohibited Substances and Methods): WADA's list of substances and methods banned in sport. WADA updates it each year. The 2026 List took effect on January 1, 2026. Source: WADA: Prohibited List resource page
PubMed: A free database of more than 40 million citations and abstracts of biomedical research, run by the National Library of Medicine. It does not hold most full-text articles. Source: PubMed (NLM): About
Randomized controlled trial (also: randomized trial, randomized trials, randomized clinical trial, randomized controlled trials, randomized, RCT, RCTs): A study in which participants are put into groups by chance, such as drug or placebo. Chance makes the groups alike, so the results can be compared fairly. Source: NIH National Cancer Institute: randomized clinical trial (Dictionary of Cancer Terms)
Receptor (also: receptors): A molecule on or inside a cell that binds a specific substance and causes a specific effect in the cell. Source: NIH National Cancer Institute: receptor (Dictionary of Cancer Terms)
Research use only (also: RUO, for research use only, research-use-only, not for human consumption): A label some online sellers put on peptides. FDA has said such labels do not stop a product from being a drug when other evidence shows it is meant for people. FDA has called such products unapproved new drugs. Source: FDA warning letter to an online peptide seller (August 24, 2026)
S0 Non-approved substances (also: S0, non-approved substances): The WADA class that bans, at all times, any drug not covered by another section and with no current government approval for human use. It includes substances still in development, such as BPC-157. Source: WADA: 2026 Prohibited List (PDF)
S2 Peptide hormones (also: S2, S2.1, S2.2, S2.3, S2.4, S2.5, peptide hormones, growth factors, related substances and mimetics): The WADA class that bans, at all times, peptide hormones, growth factors, related substances and mimetics. It names GHRH analogs, growth hormone secretagogues, GHRPs and thymosin beta-4 derivatives such as TB-500. Source: WADA: 2026 Prohibited List (PDF)
Salt form (also: salt forms, semaglutide sodium, semaglutide acetate): A version of a drug bound to a salt, such as sodium or acetate. FDA says semaglutide sodium and semaglutide acetate are different active ingredients from the one in approved semaglutide. Source: FDA: Concerns with unapproved GLP-1 drugs used for weight loss
Strict liability: The anti-doping rule that an athlete is responsible for any banned substance found in their sample. Intent, fault or knowing use do not need to be shown. Source: WADA: World Anti-Doping Code 2021 (PDF)
Subcutaneous (also: subcutaneously, under the skin): Beneath the skin. A subcutaneous injection goes into the layer just under the skin. Source: NIH National Cancer Institute: subcutaneous (Dictionary of Cancer Terms)
Synthetic (also: lab-made): Made by people, often in a lab, instead of taken from nature. Source: NIH National Cancer Institute: synthetic (Dictionary of Cancer Terms)
Systematic review (also: systematic reviews): A review that tries to find, judge and combine all the studies that meet set rules on one research question. It uses clear methods meant to reduce bias. Source: NLM Medical Subject Headings (MeSH): Systematic Review
Telomerase: An enzyme that adds DNA to telomeres, the ends of chromosomes. Cancer cells usually have more of it than normal cells. Source: NIH National Cancer Institute: telomerase (Dictionary of Cancer Terms)
Telomere (also: telomeres, telomere length): The end of a chromosome. Telomeres get a little shorter each time a cell divides. Source: NIH National Cancer Institute: telomere (Dictionary of Cancer Terms)
Therapeutic Use Exemption (also: TUE, TUEs, Therapeutic Use Exemptions): WADA permission for an athlete with an illness or medical condition to use a medicine that contains a banned substance or method. Source: WADA: Therapeutic Use Exemptions (TUEs)
Thymus (also: thymus gland): An organ in the chest behind the breastbone where T cells, a type of immune cell, grow and multiply. Source: NIH National Cancer Institute: thymus (Dictionary of Cancer Terms)
Thyroid C-cell tumor (also: thyroid C-cell tumors, C-cell tumors, C-cell tumor): A tumor of the C cells of the thyroid gland. GLP-1 drugs caused these tumors in rodents, so their labels carry a boxed warning. It is not known whether they cause them in humans. Source: DailyMed: Ozempic (semaglutide) injection label
Type 2 diabetes (also: type 2 diabetes mellitus): A disease in which blood sugar is too high because the body does not make enough insulin or does not use it well. Source: MedlinePlus (NLM): Type 2 diabetes
Unapproved new drug (also: unapproved new drugs, unapproved drug, unapproved drugs): A drug sold without FDA approval. FDA has not reviewed its safety, effectiveness or quality. Source: FDA: Unapproved drugs
USP monograph (also: USP, NF monograph, USP or NF monograph, monograph, monographs, United States Pharmacopeia): An official quality standard for a drug ingredient in the United States Pharmacopeia or National Formulary. A 503A pharmacy may use a bulk substance that has one, even if it is not on the 503A bulks list. Source: 21 U.S.C. 353a (FD&C Act section 503A), U.S. Code (govinfo)
WADA (also: World Anti-Doping Agency): The World Anti-Doping Agency, an independent international agency set up in 1999. It writes and coordinates anti-doping rules for sport, including the yearly Prohibited List. Source: WADA: Who we are
Warning letter (also: warning letters): A letter FDA sends when it finds what it believes are significant violations of federal law, such as problems with product claims. It gives the company a chance to fix the problem. Source: FDA: About warning and close-out letters
World Anti-Doping Code (also: WADA Code, anti-doping code): The core rulebook that aligns anti-doping rules across sports groups and governments around the world. The Prohibited List is one of the standards under it. Source: WADA: World Anti-Doping Code