What Is a Receptor Agonist? Plain-English Guide
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Receptor agonist

Also called agonist, receptor activator · Reviewed

Definition: A receptor agonist is a drug that binds to a receptor on a cell and switches it on, so the cell responds as it would to the body's own signal. StatPearls describes this as stimulating activity by acting directly on a receptor. Its opposite is a receptor antagonist, which binds without switching the receptor on.

Agonists you will see on labels

Receptor agonists described on current US labels.
ProductReceptor it switches onBody signal for that receptor
Ozempic, Wegovy (semaglutide)GLP-1 receptorGLP-1
Mounjaro, Zepbound (tirzepatide)GIP and GLP-1 receptorsGIP and GLP-1
Egrifta SV (tesamorelin)GRF (GHRH) receptorGrowth hormone-releasing hormone
Macrilen (macimorelin)Growth hormone secretagogue receptorGhrelin

The Egrifta SV label says tesamorelin binds and stimulates human GRF receptors with similar potency to the body's own GRF.

Why it matters when you track doses

The class name often tells you what a drug does. "GLP-1 receptor agonist" means it switches on the GLP-1 receptor. Labels use the class name in warnings too: the Zepbound label says using it with any GLP-1 receptor agonist is not recommended.

Reading a class name

  1. "Glucose-dependent insulinotropic polypeptide (GIP) receptor and GLP-1 receptor agonist" is how the Mounjaro label describes tirzepatide.
  2. That is 2 receptors switched on by 1 molecule.
  3. Semaglutide's labels name 1 receptor: GLP-1.

Common mix-ups

  • Agonist is about the receptor, not the result. Switching on a receptor can raise or lower something downstream. GLP-1 receptor agonists lower blood sugar; GHRH receptor agonists raise growth hormone.
  • Not every drug is an agonist or an antagonist. StatPearls also lists drugs with a stabilizing action that are neither, and drugs that work by direct chemical reactions.
  • Research peptides use the same words. Ipamorelin is described in a 1998 animal study as a GHRP-receptor agonist, but it has no FDA label.

Read more on Dose Track: Tirzepatide guide · Tesamorelin guide

General education drawn from labels and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your product are the final word.
Receptor antagonistA receptor antagonist is a drug that binds to a receptor but does not switch it on. By sitting in the… GLP-1 receptor agonistA GLP-1 receptor agonist is a drug that switches on the same receptor as GLP-1 (glucagon-like peptide-1),… GIP (glucose-dependent insulinotropic polypeptide)GIP (glucose-dependent insulinotropic polypeptide) is a hormone released by K cells in the upper gut after… GHRH (growth hormone-releasing hormone)GHRH (growth hormone-releasing hormone, also called GRF) is a hormone made in the hypothalamus, part of… PK/PD (pharmacokinetics and pharmacodynamics)Pharmacokinetics (PK) is what the body does to a drug: absorbing it, spreading it around, breaking it down…

Frequently asked questions

What does agonist mean in a drug name?+
It means the drug binds a receptor and switches it on. A GLP-1 receptor agonist switches on the GLP-1 receptor.
What is the opposite of an agonist?+
An antagonist. It binds the same receptor but does not switch it on, which blocks the natural signal or an agonist drug.

Sources

  1. Marino M, Jamal Z, Zito PM. Pharmacodynamics. StatPearls 2023. PMID 29939568
  2. Ozempic (semaglutide) US prescribing information, sections 2 and 12.3, DailyMed
  3. Mounjaro (tirzepatide) US prescribing information, sections 2 and 12.3, DailyMed
  4. Zepbound (tirzepatide) US prescribing information, section 2, DailyMed
  5. Egrifta SV (tesamorelin) US prescribing information, sections 1, 2, 11 and 12, DailyMed
  6. Macrilen (macimorelin) US prescribing information, sections 1 and 12, DailyMed
  7. Raun K et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol 1998. PMID 9849822

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