The words, explained

503A pharmacy (traditional compounding pharmacy)

A 503A pharmacy is an ordinary state-licensed pharmacy (or a doctor) that makes compounded medicines under section 503A of US law. State pharmacy boards are the main watchdog. It follows different, lighter rules than a drug factory.

503B outsourcing facility

A 503B outsourcing facility is a larger compounding operation that registers with the FDA and is inspected by the FDA. It is held to factory-style quality standards. The category was created by US law in 2013.

Agonist

An agonist is a substance that fits a receptor and switches it on, like a key that turns a lock. A GLP-1 receptor agonist is a medicine that switches on the GLP-1 receptor the way the body's own GLP-1 does. A dual or triple agonist can switch on more than one kind of receptor.

Albumin binding

Albumin is a protein that floats in your blood. Some peptide medicines are built with a small fatty tail so they stick loosely to albumin, which shields them and makes them leave the body more slowly. This is one way makers give a drug a longer half-life.

Amino acid

Amino acids are the small building blocks that proteins and peptides are made from. Your body uses 20 different kinds, joined in chains like beads on a string. The order of the beads decides what the finished molecule looks like and what it does.

Amylin

Amylin is a hormone made by the same pancreas cells that make insulin. It helps control blood sugar after meals and helps you feel full. A drug based on amylin has been used for diabetes, and amylin-type drugs are being studied for weight loss.

Area postrema

The area postrema is a tiny spot at the bottom of the brain that can sense chemicals in the blood. It is linked to feeling sick to your stomach. Scientists are studying whether it plays a part in the nausea some people feel with GLP-1 medicines.

Beta cell

Beta cells are special cells in the pancreas that make insulin. They release it when blood sugar goes up after a meal. They also make amylin.

Biosimilar vs generic

A generic is an FDA-approved copy of a brand-name medicine, and it must work the same way as the original. A biosimilar is a very close, but not identical, version of a biologic, which is a medicine made from living cells. A compounded version is neither of these and is not FDA-approved.

Bulk drug substance

A bulk drug substance is the raw active ingredient used to make a compounded medicine, before it is turned into a finished product. Rules limit which ingredients compounders may use. The rules exist so that patients get ingredients with a known identity and quality.

cAMP (cyclic AMP)

cAMP is a small chemical messenger made inside cells. When a hormone switches on a receptor on the outside, the cell makes cAMP, which carries the message to the parts of the cell that act on it. Scientists call it a second messenger because the hormone is the first.

Category 2 (FDA bulk drug substances)

Category 2 is a label on an FDA list for ingredients that compounders might want to use but that the FDA thinks may carry significant safety risks. If an ingredient is in Category 2, the FDA says it could take action against a compounder who uses it. The list changes over time, so the FDA page is the place to check.

Compounding

Compounding is when a pharmacist or doctor mixes or changes ingredients to make a medicine for one person's needs, for example a liquid version for someone who cannot swallow tablets. Compounded medicines are not approved by the FDA. The FDA does not check their safety, how well they work, or their quality before they are sold.

Cryo-EM (cryo-electron microscopy)

Cryo-EM is a way to take very sharp 3D pictures of tiny molecules like proteins. The molecules are frozen so fast that they hold their natural shape, and then an electron microscope images them. It was used to see what the GLP-1 receptor looks like when it is switched on.

G protein

A G protein is a tiny molecular switch inside a cell, just under the surface. When a receptor is switched on from outside, it flips the G protein, which passes the message along inside the cell. Its discovery won a Nobel Prize in 1994.

Gastric emptying

Gastric emptying is how fast food leaves your stomach and moves into the small intestine. GLP-1 slows it down, which can make you feel full for longer after eating. Slower emptying can also change how quickly other medicines are absorbed.

GIP (glucose-dependent insulinotropic polypeptide)

GIP is a second gut hormone, released after meals, that tells the pancreas to make insulin when blood sugar is high. It works alongside GLP-1. Some newer medicines are designed to act on the GIP receptor as well as the GLP-1 receptor.

GLP-1 (glucagon-like peptide-1)

GLP-1 is a hormone that your gut releases after you eat. It helps the body handle sugar from food, and it also slows the stomach and lowers appetite. Many modern diabetes and weight medicines copy what GLP-1 does.

Glucagon

Glucagon is a hormone made in the pancreas. It does the opposite job to insulin: when blood sugar is low, it tells the liver to release stored sugar. Doctors sometimes call insulin and glucagon a balancing pair.

Half-life

A drug's half-life is the time it takes for the amount of the drug in the blood to fall by half. A long half-life means the drug leaves the body slowly. Half-life describes how the body clears a medicine; it is not the same thing as how well the medicine works.

HbA1c (A1C)

HbA1c, often called A1C, is a blood test that shows your average blood sugar over the last two to three months. Sugar sticks to a protein in red blood cells, and the test measures how much has stuck. Doctors use it to find and follow diabetes.

Hypothalamus

The hypothalamus is a small area deep in the brain that helps control hunger, thirst, body temperature and many hormones. It receives signals from the gut and blood about how much energy the body has. GLP-1 medicines act partly here, according to animal studies.

Incretin

An incretin is a hormone the gut releases after you eat that tells the pancreas to release insulin. The two main ones are GLP-1 and GIP. Because of them, food you swallow triggers more insulin than the same amount of sugar given straight into a vein.

Marketing authorisation

A marketing authorisation is the official permission a regulator gives a company to sell a medicine in a country or region. It is granted only after the company has shown the medicine is safe and works well enough for its intended use. In the US the same idea is called FDA approval.

Off-label use

Off-label use means a doctor prescribes an approved medicine for something other than what it was approved for. It is generally allowed, but the regulator has not checked that the medicine is safe and works for that other use. It is different from an unapproved drug that has never been approved for anything.

PDB (Protein Data Bank)

The Protein Data Bank is a free online library of 3D shapes of proteins and other large molecules that scientists have measured. Each entry has a short code, and anyone can look at the shape. This site links to entries so you can see the shape of the molecule behind a medicine.

Peptide

A peptide is a short chain of amino acids, the small building blocks that proteins are made from. GLP-1 and amylin are peptides. Peptides are bigger than most pill-type drugs but smaller than large proteins.

Personal importation

Personal importation means bringing a medicine into a country for your own use, instead of buying it through the normal pharmacy system there. Each country has its own rules, and in the US it is generally not allowed for drugs that FDA has not approved. This entry describes only the US position; it is not legal advice.

Phase 1, 2 and 3 trials

New medicines are tested in people in steps. Phase 1 is small and checks safety, Phase 2 looks for early signs that it works, and Phase 3 is large and asks whether it truly helps.

Placebo-controlled trial

In a placebo-controlled trial, some people get the real medicine and some get a look-alike with no active drug, and usually nobody knows who got which until the end. Comparing the two groups shows what the medicine itself does. It helps separate real effects from the effects of simply expecting to feel better.

Receptor

A receptor is a protein, often on the surface of a cell, that works like a lock. A hormone or drug that fits it, like a key, sends a message into the cell. Different cells have different receptors, so the same hormone can do different jobs in different places.

Research use only (RUO)

"Research use only" is a label some sellers put on chemicals to say they are not meant for people. The label does not make a product legal to use as a medicine. The FDA looks at what a product is really intended for, not just the words on the label.

Satiety

Satiety is the feeling of being full and satisfied after a meal, which keeps you from wanting to eat again for a while. The feeling that makes you stop eating during a meal has a different name: satiation. Gut hormones such as GLP-1 send signals to the brain that help reduce how much you eat.

Small molecule

A small molecule drug is a medicine made of a small, simple chemical, like many everyday pills. Small molecules are often easy to swallow and can slip into cells. Peptides and proteins are larger and work differently.