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Exenatide

Also known as Byetta, Bydureon, Bydureon BCise, AC2993, exendin-4

First-generation GLP-1 receptor agonist for type 2 diabetes, largely withdrawn from the market.

clinically proven Metabolic & weight approved drug

At a glance

Category
Metabolic & weight
Status
approved drug
Made from
synthetic Chemically synthesised. The sequence is that of exendin-4, a peptide first isolated from the venom of the Gila monster, but no venom or animal material is used to make the medicine.
Route
subcutaneous
Half-life
mean terminal half-life 2.4 hours for the immediate-release form 5; the extended-release microsphere formulation releases drug over weeks and supports once-weekly dosing
Onset
glucose-lowering within hours of the first dose; full HbA1c effect over 8-12 weeks (immediate-release) or 6-10 weeks (extended-release)
Molecular weight
4186.6 g/mol (molecular formula C184H282N50O60S) 5
Sequence
HGEGTFTSDLSKQMEEEAVRLFIEWLKNGGPSSGAPPPS

Approved by the FDA (Byetta 2005, Bydureon 2012) and the EMA. AstraZeneca discontinued Byetta and Bydureon BCise in the United States in October 2024 for commercial rather than safety reasons, and the FDA withdrew approval of both Byetta (NDA 021773) and Bydureon (NDA 022200) effective 3 September 2025, on the applicants' own request and on the stated ground that the products were no longer marketed rather than for any safety or efficacy reason 6. A generic twice-daily exenatide (Amneal) and some non-US supplies remain available. Prescription only.

Doping status: Not listed by WADA

Checked against the WADA 2026 Prohibited List. For a specific product and country, Global DRO is the lookup athletes are expected to use — the List names substances, not brand names.

Mechanism of action

Exenatide is a synthetic version of exendin-4, a 39-amino-acid peptide originally isolated from the saliva of the Gila monster (Heloderma suspectum). It shares roughly 53% sequence identity with human GLP-1 but has a glycine at position 2 instead of alanine, which makes it resistant to cleavage by dipeptidyl peptidase-4. That single substitution is the reason a naturally occurring lizard peptide outlasts human GLP-1, whose half-life is measured in minutes.

At the GLP-1 receptor exenatide reproduces the incretin effect: glucose-dependent stimulation of insulin secretion from pancreatic beta cells, suppression of inappropriately elevated glucagon, and slowing of gastric emptying. Because the insulin effect is glucose-dependent, monotherapy carries a low intrinsic hypoglycaemia risk.

The two marketed formulations differ only in delivery. Immediate-release exenatide (Byetta) gives sharp peaks before meals and acts largely on postprandial glucose through delayed gastric emptying. Extended-release exenatide (Bydureon) embeds the same peptide in poly(D,L-lactide-co-glycolide) microspheres that erode slowly after injection, giving continuous exposure; this lowers fasting glucose more and postprandial glucose less, and causes less nausea but more injection-site nodules.

The weight effect of exenatide is real but modest — typically 2-3 kg — and clearly smaller than that of semaglutide or tirzepatide. Exenatide was never approved for weight management on its own.

What the research shows

Exenatide is one of the best-characterised GLP-1 agonists, with a large randomised programme (AMIGO for the twice-daily form, DURATION for the weekly form) and a dedicated cardiovascular outcome trial in more than 14,000 patients. The evidence is solid, but the effect sizes on both HbA1c and weight are smaller than those of the later agents, and EXSCEL did not demonstrate cardiovascular superiority. Commercially the drug has been overtaken; the withdrawal was a market decision, not a safety signal.

Research in humans

The AMIGO trials established HbA1c reductions of roughly 0.8-1.0 percentage points with 10 mcg twice daily added to metformin or a sulfonylurea. DURATION-1 (Lancet 2008, n=295) showed that once-weekly exenatide 2 mg lowered HbA1c more than 10 mcg twice daily (-1.9 vs -1.5 percentage points) with less nausea 1. EXSCEL (New England Journal of Medicine 2017, n=14,752, median 3.2 years) found a hazard ratio of 0.91 for major adverse cardiovascular events, which did not reach statistical significance for superiority; non-inferiority for cardiovascular safety was met 2. Weight loss across the programme averaged 2-3 kg.

Animal and lab research

Exendin-4 was characterised in rodent and primate models before human development. Rodent carcinogenicity studies with the extended-release formulation produced dose-dependent thyroid C-cell adenomas and carcinomas in rats, which is the basis of the Bydureon boxed warning. The immediate-release label reports the same kind of finding — benign thyroid C-cell adenomas in female rats at every dose tested — yet Byetta carries no boxed warning while Bydureon does. The difference between the two products is regulatory rather than a difference in what the rodents showed, which is worth knowing before reading the absent boxed warning as evidence of a cleaner compound.

Caveats. The pivotal trials were funded by Amylin, Eli Lilly and later AstraZeneca. Twice-daily dosing gave poor persistence in real-world use. Extended-release exenatide is immunogenic: anti-exenatide antibodies developed in a substantial minority of patients and high titres were associated with attenuated glycaemic response. Injection-site nodules were common with the microsphere formulation. Because the product has been withdrawn in major markets, no further long-term follow-up is being generated.

What it is used for

  • Type 2 diabetes mellitus, as an adjunct to diet and exercise, usually added to metformin
  • Historically used off-label for weight reduction in type 2 diabetes, though never approved for obesity
  • Studied in post-bariatric hypoglycaemia and in type 1 diabetes as an adjunct; neither is an approved use
  • Largely superseded in practice by semaglutide, dulaglutide and tirzepatide

Dosing

Dose
Immediate-release: 5 mcg to 10 mcg twice daily. Extended-release: 2 mg once every 7 days.
Frequency
twice daily (immediate-release) or once weekly (extended-release)
Route
Subcutaneous injection into the abdomen, thigh or upper arm
Duration
Chronic, for as long as glycaemic benefit is maintained
  • Immediate-release exenatide is started at 5 mcg twice daily, given at any point within the 60 minutes before the morning and evening meals; the label states it must not be given after a meal 5.
  • After one month the dose may be increased to 10 mcg twice daily 5; the one-month step exists specifically to limit gastrointestinal adverse reactions.
  • The two daily doses should be separated by approximately six hours or more 5.
  • Extended-release exenatide is 2 mg once every 7 days on the same day each week, with or without food. There is no titration.
  • A missed weekly dose can be given as soon as noticed provided the next scheduled dose is at least three days away.
  • Immediate-release exenatide is not recommended in end-stage renal disease or severe renal impairment with a creatinine clearance below 30 ml/min 5; the extended-release form is not recommended below an eGFR of 45 ml/min/1.73 m2.
  • These are the official prescribing-information schedules. This entry is reference material, not treatment advice.
  • The off-label weight-loss use exenatide once had has largely moved to stronger agents; what still circulates is a niche grey-market 'exendin-4', described under Protocols, with no published dosing basis.

These figures describe what the literature and published protocols report. They are not advice and not a dosing instruction.

Protocols

Byetta titration (type 2 diabetes)

approved product information

Source: FDA prescribing information for Byetta (DailyMed)

First month5 mcg subcutaneously twice daily, at any time within the 60 minutes before the morning and evening meal
After 1 month10 mcg twice daily

Doses are micrograms, not milligrams, and are tied to meals rather than to a fixed weekly day. The label states the dose must not be given after a meal.

Grey-market exendin-4, self-injected (user-reported)

user protocol — not validated

Source: Research-chemical vendor labelling and user forum reports

This is not a validated schedule. It is a pattern that circulates among users and sellers, reproduced because it is what people actually follow — not because it has been tested. No trial established these doses, this interval or this duration, and nobody is checking what is in the vial. Treat every number below as an assertion, not a finding.

Reported amountsroughly 5-10 mcg subcutaneously once or twice daily, echoing the old Byetta figures
Reported purposeweight loss in people without diabetes, without the meal-timing the label ties the dose to
Reported trajectorymost report abandoning it for semaglutide or tirzepatide

The label ties immediate-release exenatide to meals — twice daily within the hour before eating — and the extended-release form to one fixed weekly day. What circulates now is not the licensed product, which has been withdrawn in the United States, but grey-market 'exendin-4' powder self-injected for weight loss without that structure. The 39-residue peptide is synthesisable, so it appears in the research-chemical market, but it is a minor and shrinking presence: users describe it as weak and short-acting next to semaglutide and tirzepatide and mostly move on. There is no published basis for these self-dosing figures, and the withdrawal of the licensed brands means the off-label weight-loss use that once relied on them has largely evaporated rather than grown.

Schedules are reproduced as their source states them. Units, IU and milligrams explains why the figures are not interchangeable between products.

Reconstitution

Storage
Refrigerate at 2-8 °C, do not freeze, protect from light. An in-use immediate-release pen may be kept at up to 25 °C for 30 days. Extended-release devices may be kept at room temperature for up to 4 weeks before use.

Worked example

Not applicable. Immediate-release exenatide is supplied as a ready-to-use solution in a prefilled multidose pen. The extended-release product is supplied either as a single-dose autoinjector (BCise) already containing the microsphere suspension, or as a single-dose tray in which a fixed diluent cartridge is joined to a vial of microspheres and mixed by the user immediately before injection — a fixed device procedure, not a user-determined reconstitution.

There is no compounding step in which a user selects a diluent or a concentration. Any protocol that describes reconstituting exenatide powder with bacteriostatic water is describing an unregulated grey-market product, not the licensed medicine.

Safety

Side effects

  • Nausea — the most common adverse reaction, affecting roughly 40-44% of patients on the immediate-release form in the combination-therapy trials and decreasing over time; less frequent with the weekly form 5
  • Vomiting, diarrhoea, constipation, dyspepsia
  • Injection-site nodules and pruritus, particularly with the extended-release microsphere formulation
  • Hypoglycaemia when combined with a sulfonylurea or insulin
  • Acute pancreatitis, including haemorrhagic and necrotising cases (uncommon but reported) 5
  • Gallstones and cholecystitis
  • Acute kidney injury and worsening of chronic renal failure, sometimes in the setting of dehydration from vomiting or diarrhoea 5
  • Delayed gastric emptying, with a corresponding risk of retained gastric contents and pulmonary aspiration during anaesthesia or deep sedation
  • Anti-exenatide antibody formation, occasionally with an attenuated glycaemic response 5
  • Hypersensitivity reactions including anaphylaxis and angioedema (rare) 5
  • Drug-induced immune-mediated thrombocytopenia, which the label treats as serious enough to contraindicate any further exenatide product 5

Do not use if

  • Personal or family history of medullary thyroid carcinoma (MTC) — applies to the extended-release formulation, which carries a boxed warning for thyroid C-cell tumours
  • Multiple endocrine neoplasia syndrome type 2 (MEN 2) — same restriction as above
  • Prior severe hypersensitivity reaction to exenatide or to any of the excipients — one of only two contraindications in the Byetta label 5
  • A history of drug-induced immune-mediated thrombocytopenia from exenatide products — the other labelled contraindication 5
  • Type 1 diabetes and diabetic ketoacidosis — exenatide is not a substitute for insulin
  • Severe renal impairment or end-stage renal disease (see the eGFR thresholds under dosing)
  • History of pancreatitis — a relative contraindication; the agent should be stopped and not restarted if pancreatitis is confirmed
  • Severe gastrointestinal disease including gastroparesis
  • Pregnancy and breastfeeding — human data are inadequate
  • Note that immediate-release exenatide does not carry the thyroid C-cell boxed warning; the extended-release product does

Interactions

Delayed gastric emptying can reduce the rate and extent of absorption of oral medicines. Drugs whose effect depends on a rapid onset (analgesics) or on a threshold concentration (oral antibiotics, oral contraceptives) should be taken at least one hour before an immediate-release exenatide injection, or with a meal not accompanied by an injection. There have been postmarketing reports of increased INR with concomitant warfarin, sometimes associated with bleeding, so INR should be monitored more closely 5. Combination with a sulfonylurea or insulin substantially increases hypoglycaemia risk and usually requires reducing the dose of those agents. Exenatide should not be combined with another GLP-1 receptor agonist or with a DPP-4 inhibitor. Anaesthesia guidelines now recommend adjusting preoperative fasting because of delayed gastric emptying.

Sources