What this is
A working set of notes on GLP-1 drugs (Ozempic and friends) and what their effect on the stomach means for anyone coming in for sedation — including the twilight sedation we use in most of our cases.
The Problem in One Sentence
Ozempic slows the stomach down so much that a patient who has fasted by the normal rules can still have undigested food sitting in there when they arrive on the table.
That is the whole story. Everything else in this note is downstream of that one fact.
The whole logic, in one line
Normal fasting rules assume the stomach empties at a normal speed. These drugs break that assumption.
What the Drug Is Actually Doing
GLP-1 stands for glucagon-like peptide-1, a hormone the gut makes after a meal that, among other things, tells the stomach to slow down. The drugs in this class mimic that hormone, at a much stronger effect and lasting the whole week.
Picture a kitchen sink with the drain half-plugged. Water still goes down, just much, much slower. That is the stomach on a GLP-1 drug. A meal that normally clears in two or three hours can still be partly in there at six, eight, sometimes longer.
The drugs in this group you will hear about by name:
- Semaglutide — sold as Ozempic (for diabetes) and Wegovy (for weight loss). The one most patients are on.
- Tirzepatide — sold as Mounjaro. Newer, stronger effect on gastric emptying.
- Dulaglutide — sold as Trulicity.
- Liraglutide — sold as Victoza or Saxenda.
About one in eight Australian adults is now on one of these. They turn up in the booking list constantly, often without flagging it themselves because they think of it as a weight or diabetes drug, not an “anaesthetic” issue.
Why a Full Stomach Is the Worry
When someone is sedated, the muscles that normally keep stomach contents down relax. If there is food sitting in the stomach, it can come back up the oesophagus, and if their airway reflexes are dulled, it can go down the wrong way into the lungs. That is pulmonary aspiration, inhaling stomach contents, and it can cause a nasty chemical pneumonia or, worse, block the airway outright.
The studies bear this out. One found retained food in the stomach of 24% of Ozempic patients who had fasted properly, compared with 5% of controls. Same fasting instructions, very different stomachs.
The case reports are real
Both the FDA and the UK MHRA have updated GLP-1 drug labels to warn about aspiration during procedures. The warnings are specifically about general anaesthesia and deep sedation. That wording matters, and we’ll come back to it.
Depth of Sedation Changes the Picture
The risk is not flat across all kinds of sedation. It scales with how deeply asleep the patient is, because that is what determines whether their airway reflexes are still working.
General anaesthetic. The patient is fully out, the airway is taken over, protective reflexes are abolished. If something comes back up, it goes down. Highest risk.
Deep sedation. The patient cannot be roused easily, breathing on their own but reflexes blunted. Still high risk.
Moderate or “twilight” sedation. The kind we use for most procedures. The patient is sleepy and amnesic but still arousable, still breathing well, and crucially, the reflexes that protect the airway are still mostly there. If something comes back up, they cough and swallow it back.
Minimal sedation. A bit of midazolam for nerves. Reflexes fully intact.
This is the reason the international warnings name GA and deep sedation specifically and not twilight. One study of 155 patients on semaglutide who had eye surgery under moderate sedation reported zero aspiration events.
Lower risk is not no risk
Twilight sedation can drift deeper than intended, particularly with bigger doses, in older patients, or when the case runs long. Patients with reflux or active GI symptoms are also higher risk regardless of how light you keep the sedation. The cautious approach applies even in twilight cases.
The 24-Hour Liquid Diet
The 2025 Australian recommendations (joint guidance from ANZCA, the Australian Diabetes Society, and the gastro and surgical colleges) land on this rule for anyone on a GLP-1 drug coming in for a procedure under anaesthesia or sedation:
The day before the procedure: clear fluids only. Then standard nil-by-mouth from midnight (or six hours pre-procedure, whichever applies).
Clear fluids means things you can read a newspaper through — water, black tea or coffee, clear apple juice, clear broth, jelly, ice blocks. No milk, no smoothies, no protein shakes, no soup with bits in it.
The thinking is that 24 hours on liquids gives even a sluggish stomach time to empty, so by the time the patient arrives, there is nothing solid in there to come back up. It is a workaround for the fact that the drug itself cannot be safely stopped (more on that in a second).
The Australian guidelines apply this rule to sedation as well as GA, with no exception for twilight. So even though the data suggests the risk in twilight is much lower, the dietary preparation is the same.
Why We Do Not Just Stop the Drug
The intuitive answer is “tell them to skip it for a week before the procedure.” The guidelines specifically say not to.
Two reasons. First, these drugs sit in the body for a long time. Semaglutide has a half-life of about a week. Stopping it one or two weeks out does not reliably restore normal gastric emptying, the stomach is still slow. Second, stopping creates its own problems: diabetics lose glucose control, weight-loss patients can rebound, and you have traded an aspiration risk you were going to manage with diet for a new metabolic problem you are not.
So the rule is: keep taking the drug, but prepare the gut with a liquid day.
This is conditional advice
The guidelines themselves admit the evidence base is thin, mostly case reports and retrospective data. A formal review is due in 2026. The current rules are deliberately cautious because the consequences of aspiration are bad, even if the absolute risk is low.
Who Needs a Second Look
Some patients on GLP-1 drugs are higher risk than others, and worth flagging for the proceduralist:
- Anyone with active GI symptoms on the drug (nausea, vomiting, feeling full all the time, reflux, bloating). These are signs the gastric emptying is meaningfully impaired right now.
- Patients on higher doses or who have only recently started. The gastric effects are strongest in the dose-escalation phase.
- Patients on tirzepatide (Mounjaro), which has a stronger gastric effect than the older agents.
- Patients with co-existing reflux disease or known gastroparesis.
- Cases where deeper sedation may be needed than originally planned (longer cases, larger patients, anxious patients).
If any of these apply and the 24-hour liquid prep has not been done, the options the team can consider are postponing, doing a quick gastric ultrasound at the bedside to see what is in there, or moving to a regional or local technique with minimal sedation if the procedure allows.
What This Looks Like in the Room
The practical knock-on for our list is mostly at the front end, booking and the morning of.
At booking, the screening question is now standard: “Are you on any medications for diabetes or weight loss, including Ozempic, Wegovy, Mounjaro, Trulicity, or Saxenda?” Patients often do not volunteer it. They might list it under “vitamins and supplements” or not at all because they think of it as a lifestyle drug.
The pre-procedure instructions for these patients carry the extra step: clear fluids only the day before. This needs to be in writing on the confirmation letter, not just mentioned over the phone.
On the day, the check-in question is direct: “Were you able to stick to clear fluids only yesterday?” If the answer is no, that gets flagged to the proceduralist before the patient is brought through.
In the room itself, you might hear the consultant ask the patient one more time about their last meal, or ask the reg to do a quick gastric scan before starting sedation if there is doubt. If you are setting up, having suction ready and within reach is part of the standard kit anyway, but in these cases it earns its place. The trolley does not change for these patients. What changes is the readiness to use what is on it.
Quick Reference
| Question | Answer |
|---|---|
| Should the patient stop their GLP-1 drug? | No. Keep taking it. |
| What diet the day before? | Clear fluids only, for 24 hours. |
| Standard fasting after that? | Yes — nil by mouth from midnight or 6 hours pre-procedure. |
| Does this apply to twilight sedation? | Yes, per Australian guidelines. |
| Highest-risk patients to flag? | Active GI symptoms, recent starters, high doses, tirzepatide, reflux disease. |
| If they did not do the liquid prep? | Flag to proceduralist — options include postponing, gastric ultrasound, regional technique. |
Related
- CT-Guided Spinal Injections — most of our injection list runs on twilight sedation
- Suprapubic Catheter Insertion — Stab Technique — sedation case where retained gastric content matters
- Fiducial Insertion into Deep Organs — sedation depth varies with case complexity
Sources
- NACOS Clinical Practice Recommendations (full text)
- GIP RAs Clinical Guidance Updated (April 2025)
- ADS April 2025 — Full Recommendations PDF
- ASA 2024 Multi-Society GLP-1 Guidance
- APSF — Retained Gastric Contents Case Reports
- UK MHRA — GLP-1 Aspiration Risk Drug Safety Update
- Moderate Sedation Eye Surgery Study — Zero Aspiration Events
- GLP-1 RAs and Conscious Sedation Review (2025)
- Perioperative Management of GLP-1RAs — Aspiration Risk Review
- RACS Updated Guidance Summary (2025)
Last updated May 18, 2026.