What are GLP-1 receptor agonists and how do they work?
GLP-1 (glucagon-like peptide-1) is a hormone produced in the intestine in response to food intake. Natural GLP-1 is active for only a few minutes before enzymes called dipeptidyl peptidases (DPP-4) degrade it. GLP-1 receptor agonists are synthetic molecules engineered to resist that degradation and provide sustained receptor engagement.
The GLP-1 receptor is expressed in multiple organ systems:
- Hypothalamus and brainstem: Where GLP-1 signaling suppresses appetite and modulates satiety perception. This is the mechanism most relevant to weight management.
- Pancreatic beta cells: Where GLP-1 supports insulin secretion in a glucose-dependent fashion (meaning it does not drive insulin release when blood sugar is already normal, reducing hypoglycemia risk).
- Stomach: Where GLP-1 slows gastric emptying, which contributes to satiety and postprandial glucose management — and which accounts for the GI side effects many patients experience.
- Liver and cardiovascular tissue: Where emerging research continues to characterize additional effects.
What drugs are in the GLP-1 agonist class? Complete medications list.
Below is every agent in or closely related to the GLP-1 receptor agonist class, with clinical context for each.
Semaglutide
Wegovy / Ozempic (branded)
Most widely used injectable for weight management. Half-life ~1 week. Available as compounded preparation through licensed 503A pharmacies during shortage designation.
Tirzepatide
Zepbound / Mounjaro (branded)
Dual mechanism drives stronger average weight reduction than single GLP-1 agonists in trial data. Available as compounded preparation through licensed 503A pharmacies during shortage designation.
Liraglutide
Saxenda / Victoza (branded)
Shorter half-life requires daily dosing. Earlier entry in the class; FDA-approved for weight management at the Saxenda dose. Less average weight reduction than semaglutide in head-to-head data.
Dulaglutide
Trulicity (branded)
Weekly dosing, primarily used in metabolic conditions. Not specifically approved or commonly used for weight management protocols.
Exenatide
Byetta / Bydureon (branded)
Earlier GLP-1 agent. Exendin-4 based (lizard-derived sequence), not a human GLP-1 analog. Less commonly used in modern weight management protocols given newer alternatives.
Lixisenatide
Adlyxin / Lyxumia (branded)
Short-acting; primarily affects postprandial glucose. Limited weight management data compared to semaglutide or tirzepatide.
Albiglutide
Tanzeum / Eperzan (branded, discontinued)
Commercially discontinued. Included here for completeness; not available in practice.
What distinguishes one GLP-1 agonist from another?
Several dimensions distinguish agents within the GLP-1 agonist medications list:
- Half-life and dosing frequency: Longer-acting agents (semaglutide, tirzepatide, dulaglutide, albiglutide) enable once-weekly dosing. Shorter-acting agents (liraglutide, lixisenatide, immediate- release exenatide) require daily or twice-daily dosing. Weekly dosing improves adherence for most patients.
- Molecular structure: Most GLP-1 receptor agonists are based on modifications of human GLP-1 sequence. Exenatide is based on exendin-4, a peptide found in Gila monster venom — a distinct structural lineage. This affects immunogenicity profiles.
- Single vs. dual receptor targeting: Tirzepatide’s dual GIP/GLP-1 mechanism is the most significant pharmacological distinction in the modern class. The GIP receptor activation appears to complement the GLP-1 signal in ways that produce stronger average weight reduction than single-agonist agents.
- Clinical trial weight data: Not all agents have been studied specifically for weight management. Semaglutide and tirzepatide have the most robust weight-focused clinical trial programs. Liraglutide has supporting data. Dulaglutide and exenatide were primarily developed for metabolic management.
Which GLP-1 agonists can be compounded?
During FDA-designated shortage periods for branded semaglutide and tirzepatide injectables, licensed 503A compounding pharmacies have been permitted to compound patient-specific preparations. These are the primary agents available through clinician-supervised telehealth weight management programs.
Compounded semaglutide and tirzepatide are not FDA-approved drugs — they are compounded preparations. Compounded in the USA by licensed 503A pharmacies. No hidden overseas supply chain.
Liraglutide, dulaglutide, and exenatide are not commonly available through compounding channels for weight management purposes. The clinical focus in compounded weight management programs is semaglutide and tirzepatide.
How does a clinician choose between GLP-1 agents?
A clinician reviewing a patient for GLP-1 receptor agonist therapy for weight management considers:
- Weight management goals and timeline — patients with more significant weight management goals may benefit from agents with larger average trial outcomes (tirzepatide), though individual response varies.
- GI tolerance history — different agents within the class have similar GI side effect profiles, but individual response is variable. Prior experience with a GLP-1 agent informs what to expect.
- Medical comorbidities — clinical history shapes eligibility and may favor specific agents.
- Concurrent medications — potential interactions with other prescriptions are evaluated at intake.
No medication in the GLP-1 class should be self-selected. These are prescription medications that require clinician evaluation.
Frequently asked questions
What drugs are in the GLP-1 agonist class?
The main GLP-1 receptor agonists include semaglutide, tirzepatide (dual GLP-1/GIP), liraglutide, dulaglutide, exenatide, albiglutide, and lixisenatide. Semaglutide and tirzepatide are the most studied for weight management and produce the largest average weight reductions in clinical trials.
Is tirzepatide a GLP-1 agonist?
Tirzepatide is a dual agonist — it activates both the GLP-1 receptor and the GIP (glucose-dependent insulinotropic polypeptide) receptor. While often grouped with GLP-1 agonists for clinical purposes, its dual mechanism distinguishes it pharmacologically and appears to drive stronger average weight reduction than single GLP-1 receptor agonists in head-to-head data.
What is the difference between semaglutide and liraglutide?
Both are GLP-1 receptor agonists, but semaglutide has a longer half-life (approximately one week vs. 13 hours for liraglutide), allowing once-weekly vs. once-daily injection. Clinical trial data shows semaglutide produces greater average weight reduction. Liraglutide was the earlier entry in the class and was the first injectable approved for weight management.
Which GLP-1 agonist is best for weight loss?
Clinical trial data shows tirzepatide at 15 mg weekly (average ~20% body weight reduction in SURMOUNT-1) outperforms semaglutide at 2.4 mg weekly (average ~15% in STEP 1) in average outcomes. However, individual response varies substantially. The best option for a specific person depends on their clinical history, tolerability, and what their clinician determines is appropriate.
Are GLP-1 agonists available as pills?
Oral semaglutide (Rybelsus) exists as an FDA-approved pill for metabolic conditions, but the doses approved for that indication are lower than those used in weight management protocols, and the oral formulation has lower bioavailability. Most weight management protocols use injectable GLP-1 receptor agonists.
Can GLP-1 agonists be compounded?
Compounded semaglutide and tirzepatide have been available through licensed 503A pharmacies during FDA-designated shortage periods for the branded injectables. Compounded formulations are patient-specific and require a clinician prescription. Liraglutide, dulaglutide, and exenatide are not commonly compounded in the same way.
Learn more about compounded semaglutide or compounded tirzepatide available through clinician-supervised protocols.