What Medications Interfere with a Gastric Emptying Study?

October 14, 2025 •

4 min read

According to the American Neurogastroenterology and Motility Society, certain medications that affect gastrointestinal motility must be stopped before a gastric emptying study to avoid inaccurate results. Understanding what medications interfere with a gastric emptying study is crucial for accurate diagnosis and patient preparation.

Quick Summary

Certain medications, including opioids, prokinetics, anticholinergics, and specific diabetes drugs, can significantly alter the results of a gastric emptying study by affecting gastrointestinal motility. Stopping these medications for a prescribed period before the test is essential to ensure a correct diagnosis and avoid misinterpretation of symptoms.

Key Points

Opioids and Painkillers: Opiate analgesics like codeine and morphine are known to delay gastric emptying and must be stopped 48-72 hours before the study.
Prokinetic Drugs: Medications like metoclopramide (Reglan) and erythromycin, which accelerate gastric motility, can mask underlying issues and should be discontinued.
GLP-1 Agonists: Newer diabetes and weight loss drugs such as semaglutide (Ozempic) can significantly delay gastric emptying and may require up to a four-week washout period.
Anticholinergics and Antispasmodics: Drugs like dicyclomine (Bentyl) slow gastrointestinal movement and should be held for two to three days before the test.
Diabetes Management: Patients with diabetes must coordinate with their doctor to manage insulin and blood glucose levels during the fasting and testing period.
Physician Consultation is Essential: Never stop any medication without first discussing it with a healthcare provider, as individual patient needs and institutional protocols can vary.
Avoid All Unprescribed Drugs: This includes marijuana and potentially other sedatives, as they can also interfere with gastric motility.

A gastric emptying study, or gastric emptying scintigraphy (GES), is a nuclear medicine procedure used to measure the rate at which food leaves the stomach and enters the small intestine. It is a standard diagnostic tool for conditions affecting gastric motility, such as gastroparesis. For the results to be accurate, the patient's normal gastric motility must be assessed without the confounding effects of outside agents. Many common medications can alter the speed of gastric emptying, and healthcare providers must instruct patients to temporarily stop these drugs before the study. Below is a comprehensive look at the medication classes known to interfere.

Medications that Delay Gastric Emptying

Several types of medications can slow down the digestive process, leading to delayed gastric emptying. If taken before a GES, these drugs could mimic the symptoms of gastroparesis and result in a false-positive diagnosis.

Opioid Analgesics

Opioid pain relievers are one of the most common causes of delayed gastric emptying. They work by binding to opioid receptors in the brain and gut, which can slow down gastrointestinal motility significantly.

Examples: codeine, morphine, oxycodone (Percocet, OxyContin), hydrocodone (Vicodin), fentanyl, tramadol (Ultram), and methadone.
Patient Instructions: Opioids are typically stopped for at least 48 to 72 hours before the study, though the exact timing should be confirmed with the ordering physician.

Anticholinergic and Antispasmodic Drugs

These medications are used to reduce muscle spasms in the gut, but in doing so, they also slow down overall gastric movement.

Examples: dicyclomine (Bentyl), atropine, hyoscyamine (Levsin), and propantheline.
Patient Instructions: These drugs are generally held for two to three days before the test.

GLP-1 Receptor Agonists

This newer class of medications, used for diabetes management and weight loss, has a well-known side effect of delaying gastric emptying. This effect is critical for their therapeutic function, but it can completely invalidate a GES.

Examples: semaglutide (Ozempic, Rybelsus), liraglutide (Victoza), dulaglutide (Trulicity), and exenatide (Byetta).
Patient Instructions: Due to their long-acting nature, some healthcare providers require these drugs to be stopped for up to four weeks before a study.

Other Agents

Proton Pump Inhibitors (PPIs): While not universally required to be stopped, some studies show that PPIs can cause delayed gastric emptying by altering digestive processes, and some institutions may recommend temporarily discontinuing them.
Cannabis (Marijuana): Cannabinoids can affect gut motility and are often recommended to be avoided before the study.

Medications that Accelerate Gastric Emptying

Certain medications are designed to speed up the rate of gastric emptying. If a patient takes one of these drugs before a GES, it could normalize or even accelerate the results, masking an underlying issue of delayed emptying.

Prokinetic Agents

These are medications specifically prescribed to treat gastroparesis by speeding up the movement of food through the stomach.

Examples: metoclopramide (Reglan), domperidone (Motilium), cisapride, and erythromycin.
Patient Instructions: It is critical to stop these medications, usually for 48 to 72 hours, unless the study is being performed specifically to assess the medication's efficacy.

Managing Diabetic Medications and Conditions

Diabetes itself is a common cause of gastroparesis, and managing blood sugar is a crucial part of preparing for a GES. Patients with diabetes must follow specific instructions to avoid both hypoglycemia and hyperglycemia, which can influence gastric emptying.

Pre-test management: The patient's endocrinologist or primary care physician will provide a plan for insulin or oral hypoglycemic medication adjustment for the day of the test.
Insulin: Patients on insulin may need to bring their morning dose and adjust it based on the test meal, which is usually a smaller, controlled portion of food.
Oral Hypoglycemics: The timing of oral medications may be adjusted to be taken with the test meal.
Blood Glucose Targets: Ideally, blood glucose should be maintained near normal levels, often below 200 mg/dL, to ensure an accurate test.

Why Accurate Results are Crucial

Failing to stop interfering medications can have significant consequences for a patient's diagnosis and treatment plan. A false-positive result could lead to unnecessary prescriptions and side effects, while a false-negative result could delay the diagnosis of a genuine motility disorder, prolonging the patient's symptoms.

Comparative Overview of Gastric Motility-Affecting Medications


Medication Class	Examples	Effect on Gastric Emptying	Typical Action to Take Before GES
Opioid Analgesics	Morphine, Oxycodone	Slows down motility (delays emptying)	Stop for 48-72 hours
Anticholinergics	Dicyclomine (Bentyl)	Slows down motility (delays emptying)	Stop for 48-72 hours
GLP-1 Agonists	Semaglutide (Ozempic)	Slows down motility (delays emptying)	May require up to 4 weeks to stop
Prokinetic Agents	Metoclopramide (Reglan), Erythromycin	Speeds up motility (accelerates emptying)	Stop for 48-72 hours (unless testing efficacy)
Proton Pump Inhibitors	Omeprazole, Lansoprazole	Can cause variable delays	Consult physician; may require temporary hold
Cannabinoids	Marijuana	Can affect motility	Avoid prior to test

The Importance of Physician Consultation

Patients should never stop or adjust their medication regimen without first consulting the prescribing physician or the nuclear medicine department. Some tests might be performed specifically to evaluate the effect of a medication, and a provider will weigh the risk of temporarily withholding treatment against the benefit of an accurate diagnostic result. The preparation instructions can vary depending on the patient's overall health, the specific medication, and the protocol of the testing facility.

Conclusion

The accuracy of a gastric emptying study relies heavily on proper patient preparation, including the temporary cessation of certain medications. From opioids and GLP-1 agonists that delay motility to prokinetic agents that accelerate it, numerous drugs can significantly skew test results. By proactively communicating with healthcare providers and strictly following the prescribed preparation guidelines, patients can ensure that their GES provides the most accurate and reliable information possible for an effective treatment plan.

Frequently Asked Questions

Opioid painkillers such as codeine, morphine, oxycodone (Percocet), hydrocodone (Vicodin), fentanyl, and tramadol (Ultram) interfere with the study by slowing down gastric emptying. They must be discontinued for a period of time before the test, as directed by your doctor.

Specific diabetes medications must be managed carefully before a gastric emptying study. GLP-1 agonists like Ozempic (semaglutide) must be stopped, sometimes for several weeks. Your doctor will provide a specific plan for insulin or other oral medications, often adjusting the dose for the test meal.

The timeframe for stopping interfering medications varies by drug type. For opioids and prokinetics, it is often 48 to 72 hours, while GLP-1 agonists may require up to four weeks. Always follow your physician's specific instructions.

While not always necessary, some studies suggest that PPIs can delay gastric emptying. You should discuss this with your physician, as they may decide to temporarily hold your PPI, depending on your symptoms and the testing protocol.

The main risk is receiving an inaccurate test result. Medications that slow down emptying can cause a false-positive diagnosis of gastroparesis, while medications that speed it up can mask a real motility problem, leading to delayed or incorrect treatment.

These drugs, like dicyclomine, are designed to relax muscles and reduce spasms in the gastrointestinal tract. This action also slows down the normal, rhythmic contractions that move food through the stomach, thereby interfering with the test results.

No, fasting is required before the study, typically for 12 hours, to ensure an accurate baseline measurement. You will be given a specific, controlled meal during the test.