Exenatide: the first GLP-1 receptor agonist

A peptide first found in a lizard

The Byetta® label describes exenatide as a synthetic peptide originally identified in the lizard Heloderma suspectum ^[1]. It is 39 amino acids long, and its sequence partly overlaps that of human GLP-1, the gut hormone that helps control blood sugar after meals ^[1].

Exenatide activates the human GLP-1 receptor. According to the label, this raises insulin release from the pancreas when blood sugar is high, suppresses glucagon that is inappropriately raised, and slows stomach emptying ^[1]. It does not block the body’s normal glucagon response when blood sugar falls too low ^[1].

Two forms, two schedules

• Byetta® (exenatide) injection: a prefilled pen used twice a day, within the hour before the morning and evening meals or before the two main meals of the day about six hours or more apart, never after eating. Each pen held 60 doses ^[1]. A missed dose was skipped and the next one taken at its usual time ^[1].
• Bydureon BCise® (exenatide extended-release): a single-dose autoinjector given once every seven days, at any time of day ^[2]. The exenatide sits in tiny polymer microspheres suspended in an oil and is released slowly ^[2]. The device had to be shaken hard for at least 15 seconds before use ^[2]. A missed dose could be given once noticed if the next one was at least 3 days away ^[2].
• The two were not meant to be combined: each label advises against using it with other exenatide-containing products ^[1][2].

Why the schedules differ so much

Exenatide on its own is cleared quickly, mainly by filtration in the kidneys ^[1]. The Byetta® label gives a mean terminal half-life of 2.4 hours, with levels measurable for roughly 10 hours after a dose in most people ^[1].

Bydureon BCise® works around this with its microspheres. A single dose peaks around week 6 to 7, and with weekly dosing levels climb gradually and reach a steady state at about week 10 ^[2]. The other side is a long tail: about 10 weeks after the last dose, levels generally fall below the measurable limit ^[2]. That tail is why the label warns that low platelets can persist for about 10 weeks after stopping ^[2].

Who it was approved for

Both labels are for type 2 diabetes only, as an addition to diet and exercise. Byetta® is labelled for adults; its label notes that effectiveness was not shown in a trial of 120 children aged 10 to 17 ^[1]. Bydureon BCise® is labelled for adults and children aged 10 and older ^[2].

Neither label includes weight management or a heart-risk indication. In the EXSCEL trial, 14,752 adults with type 2 diabetes took the earlier extended-release form, Bydureon®, or placebo for a median of 38.7 months ^[2]. Major cardiovascular events occurred in 11.4% versus 12.2%, a hazard ratio of 0.91 ^[2][10]. Exenatide met the test for not increasing cardiovascular risk but did not show a reduction, and the published paper, funded by Amylin Pharmaceuticals, reached the same conclusion ^[10].

Where exenatide stands in 2026

Exenatide left the market through a series of regulatory notices rather than a single announcement. The table gathers what the official records show as of October 2026. Withdrawal of approval under this procedure is, in the notices’ own words, without prejudice to refiling, and stock already on hand on the effective date could still be dispensed until it ran out or expired ^[5][6].

Warnings specific to exenatide

• Low platelets: serious bleeding, sometimes fatal, has been reported from an immune reaction in which antibodies destroy platelets in the presence of exenatide. Both labels make a history of this reaction a reason never to use exenatide again ^[1][2].
• Antibodies: people can develop antibodies to exenatide. In the Byetta® trials, antibody formation came with a weaker blood sugar response in 1% to 4% of patients, depending on the study ^[1].
• Injection-site reactions with Bydureon BCise®: a lump under the skin (nodule) was its most common reaction, in 10.5% of adults in the pooled trials ^[2]. The label also describes serious site reactions after approval, including abscess, cellulitis and tissue death, with the earlier Bydureon® form; isolated cases needed surgery ^[2].
• Warfarin: reports of a raised INR, sometimes with bleeding, led both labels to ask for frequent INR checks when exenatide is started or changed ^[1][2].
• Kidneys: Byetta® is not recommended in severe kidney impairment or end-stage kidney disease, and Bydureon BCise® not below an eGFR of 45 ^[1][2].

Warnings it shares with other GLP-1 medicines

Both labels include pancreatitis, low blood sugar when combined with insulin or a sulfonylurea, kidney injury linked to dehydration, severe stomach reactions, serious allergic reactions, gallbladder disease and the risk of inhaling stomach contents during anaesthesia or deep sedation ^[1][2]. Because exenatide slows stomach emptying, the Byetta® label also asks for care with oral medicines whose absorption speed matters ^[1].

One difference stands out. Bydureon BCise® carries the boxed warning about thyroid C-cell tumours seen in rats and must not be used by anyone with medullary thyroid cancer or MEN 2 in their own or family history ^[2]. The Byetta® label has no boxed warning, although its animal section reports benign thyroid C-cell growths in female rats ^[1].

Common side effects

Nausea leads the Byetta® list of common reactions, followed by low blood sugar, vomiting, diarrhoea, feeling jittery, dizziness, headache, indigestion, constipation and weakness; the label says nausea usually eases with time ^[1].

For Bydureon BCise®, only two reactions reached 5% in the pooled trials: injection-site nodules in 10.5% and nausea in 8.2% ^[2]. Headache, diarrhoea, vomiting, itching and redness at the site, dizziness and constipation each occurred in more than 2% but under 5% ^[2].

If you or someone you care for used exenatide

Anyone still holding Byetta® or Bydureon BCise® pens should check the expiry dates and talk to the prescriber about what comes next; choosing another medicine and how to start it is the prescriber’s decision. The Bydureon BCise® label notes that people moving from immediate-release exenatide to the weekly form saw blood sugar rise for about 2 to 4 weeks, which shows how much the timing of these products matters ^[2].

A history of exenatide-induced low platelets is worth keeping on record for any future prescriber, since both labels treat it as a lasting reason to avoid exenatide ^[1][2]. So is the date of the last weekly dose, given the roughly 10-week tail ^[2].

Byetta®, Bydureon® and Bydureon BCise® are trademarks of the AstraZeneca group of companies. PepLabo is not affiliated with or endorsed by AstraZeneca or any generic manufacturer.

When to get help