Gastroparesis

Gastroparesis is a syndrome of symptoms suggesting retention of food in the stomach together with objective evidence of delayed gastric emptying, in the specific absence of any mechanical obstruction in the gastric outflow tract.^[1] Both halves of that definition matter equally: gastroparesis is never diagnosed on symptoms alone, and it is never diagnosed on a delayed-emptying test result alone — a patient needs both the compatible symptom pattern and objectively demonstrated delayed emptying, with mechanical obstruction excluded by upper endoscopy or imaging before either is attributed to a motility disorder.^[1]

Gastroparesis is not itself a single disease but the downstream result of impaired gastric motor function — most often from dysfunction of the vagus nerve, the intrinsic enteric nervous system, or the interstitial cells of Cajal (the stomach's pacemaker cells) — that disrupts the normally coordinated sequence of fundic accommodation, antral grinding, and pyloric emptying needed to move a meal out of the stomach and into the duodenum on schedule.

How common this actually is

Gastroparesis is uncommon but not rare, and it disproportionately affects women. In the population-based Olmsted County, Minnesota study, the age-adjusted incidence of definite gastroparesis (delayed emptying by scintigraphy plus typical symptoms persisting more than 3 months) was 2.4 per 100,000 person-years in men versus 9.8 per 100,000 person-years in women, and the age-adjusted prevalence as of January 1, 2007 was 9.6 per 100,000 in men versus 37.8 per 100,000 in women — a roughly four-fold female predominance at every stage.^[3] Overall survival in that cohort was significantly lower than expected for the general population, underscoring that gastroparesis is not a benign nuisance diagnosis once it is established.^[3]

Etiology — what is actually most common depends on how you look

A large, real-world US national claims-database analysis found diabetes to be the most frequently coded etiology overall — 57.4% of cases (type 1 diabetes 5.7%, type 2 diabetes 51.7%) — followed by post-surgical (15.0%), drug-induced (11.8%), and idiopathic (11.3%) gastroparesis.^[4] This differs from the pattern often quoted from smaller, tertiary-referral-center cohorts, where idiopathic disease is described as the largest single category; the claims-database figures reflect a broader, more representative real-world population and are the more current estimate of relative frequency.^[4]

Clinical presentation

The cardinal symptoms are early satiety, postprandial fullness, nausea, vomiting (often of partially digested food, sometimes hours after the meal that caused it), bloating, and upper abdominal discomfort.^[1] Unintentional weight loss signals more severe or advanced disease and should prompt closer nutritional attention — see Treatment Targets and Complications within Red Flags & Referral.

• Diabetes mellitus — the single most commonly coded etiology in real-world data, driven predominantly by type 2 diabetes numerically but with disproportionate representation from type 1 diabetes relative to its overall prevalence.^[4]
• Female sex — a consistent, roughly four-fold predominance across incidence and prevalence figures and across etiologic subtypes.^[3]
• Prior upper gastrointestinal or bariatric surgery with vagal nerve injury risk — fundoplication, vagotomy, sleeve gastrectomy, and Roux-en-Y gastric bypass are the procedures most often implicated.^[4]
• A preceding viral prodromal illness — frequently reported before idiopathic gastroparesis onset.
• Connective tissue disease (scleroderma), Parkinson's disease, and other conditions affecting autonomic or enteric nerve function.
• Opioid use — slows gastric emptying directly and is a named, deprescribing-relevant contributor.^[5]
• Anticholinergic drug use — reduces gastric motility through the same mechanism it reduces salivary flow and gut motility generally.
• GLP-1 receptor agonist or tirzepatide use — slows gastric emptying by design and can unmask or worsen gastroparesis; a genuinely current and increasingly common contributor given how widely these drugs are now used.^[6][5]
• Poor long-term glycemic control in diabetes — chronic hyperglycemia is the mechanism behind diabetic gastroparesis, and Diabetes Canada's guideline itself suggests optimal glucose control to reduce the future risk of aggravating established disease.^[5][1]

Step 1 — exclude mechanical obstruction

Before any gastroparesis-specific test is ordered, upper endoscopy or an imaging study must exclude a mechanical cause of gastric outflow obstruction — a stricture, tumour, or other structural lesion. This step is not optional or a formality; it is the definitional prerequisite for the diagnosis.^[1]

Step 2 — achieve adequate glycemic control and hold motility-affecting medications before testing

Acute hyperglycemia itself delays gastric emptying, independent of any underlying diabetic neuropathy — data from the Diabetes Control and Complications Trial and its follow-up (the EDIC study) showed delayed gastric emptying was associated with both gastrointestinal symptoms and measures of both early and long-term hyperglycemia.^[1] Testing during a hyperglycemic episode can therefore produce a falsely delayed result that reflects the moment's blood glucose rather than a true underlying motility disorder. The original 2008 consensus recommendation was to defer testing, or actively lower glucose with insulin, if serum glucose exceeds 275 mg/dL (15.3 mmol/L) at the time of the study; subsequent practice has tightened this further, generally targeting blood glucose under 200 mg/dL (11.1 mmol/L) before proceeding.^[8] It is also customary to hold medications that affect gastric emptying — prokinetics, opioids, anticholinergics, and cannabinoids — for 48 hours before testing wherever clinically safe to do so, since each can independently speed or slow the result.^[1]

Step 3 — gastric emptying scintigraphy: the standard test

Scintigraphic gastric emptying (SGE) of a solid meal is the standard test for evaluating gastroparesis in patients with upper gastrointestinal symptoms (strong recommendation, moderate-quality evidence).^[1] The test should assess emptying of a solid meal over a duration of 3 hours or more — in practice, a 4-hour protocol, with imaging at baseline and at 1, 2, and 4 hours after a standardized low-fat solid meal.^[8] Gastric retention of 60% or more at 2 hours, or 10% or more at 4 hours, defines delayed gastric emptying.^[8][1] A shorter study can miss real disease: relying on only 1 or 2 hours of imaging risks a false-negative result in a meaningful proportion of patients who would otherwise be identified with the full 4-hour protocol.

Alternative and adjunct tests

• Wireless motility capsule (WMC) — a reasonable alternative to scintigraphy (conditional recommendation, low-quality evidence); it also provides information about small bowel and colonic transit, useful when extra-gastric dysmotility is suspected.^[1]
• Stable isotope (¹³C-spirulina) breath test — a reliable alternative for evaluating gastric emptying in patients with upper gastrointestinal symptoms (conditional recommendation, low-quality evidence).^[1]
• Radiopaque marker (ROM) testing — specifically not suggested for the diagnostic evaluation of gastroparesis; it is meaningfully less accurate than scintigraphy at assessing emptying of digestible solid food (conditional recommendation, very-low-quality evidence).^[1]

Confounders — what does not, by itself, confirm the diagnosis

Retained gastric food seen incidentally at upper endoscopy is frequently identified but should not automatically be treated as diagnostic of gastroparesis on its own — in one large retrospective series, the positive predictive value of retained gastric food for a delayed-emptying result ranged from 32% in patients without risk factors up to 79% in patients with type 1 diabetes, and confounding by medications that themselves slow emptying should be excluded before attributing it to gastroparesis.^[1] There is also genuine, clinically important overlap between gastroparesis and functional dyspepsia: in one cohort, 42% of patients initially diagnosed with gastroparesis were reclassified based on the presence or absence of delayed emptying on repeat testing, and 37% of patients diagnosed with functional dyspepsia were found to have delayed emptying on the same repeat testing — the degree of gastric emptying delay can genuinely fluctuate over time in the same patient.^[1]

• Control symptoms — early satiety, fullness, nausea, vomiting, and bloating — to a level that allows adequate oral nutrition and an acceptable quality of life.
• Maintain nutritional adequacy and prevent unintentional weight loss, escalating through the nutrition ladder (oral, then enteral, rarely parenteral) before malnutrition becomes established rather than after.
• In diabetic gastroparesis specifically, optimize glycemic control — this is a genuinely bidirectional goal, since chronic hyperglycemia is a cause of diabetic gastroparesis and acute hyperglycemia independently worsens gastric emptying and confounds its own assessment.
• Identify and address reversible contributors before adding a prokinetic — review for opioids, anticholinergic drugs, and GLP-1 receptor agonists/tirzepatide that may be causing or worsening the picture.
• Use metoclopramide, when needed, at the lowest effective dose for the shortest duration, with a hard ceiling of 12 weeks absent an explicit, documented risk-benefit reassessment — minimizing exposure to its tardive dyskinesia risk is a treatment goal in its own right, not an afterthought to efficacy.
• Avoid reaching for therapies current evidence specifically does not support (central neuromodulators, ghrelin agonists, haloperidol, intrapyloric botulinum toxin) simply because a patient remains symptomatic.
• Recognize refractory disease early and refer for gastric electrical stimulation or pyloric intervention evaluation rather than escalating ineffective medical therapy indefinitely.
• Educate the patient on the dietary pattern, the medication-specific safety counseling points, and the symptoms that should prompt them to stop a drug and seek care.

Domperidone — a genuinely Canada-specific access point

Where domperidone is approved, current guidance suggests its use for symptom management (conditional recommendation, low-quality evidence).^[1] Available and prescribable in Canada domperidone has been an approved, DIN-bearing prescription drug in Canada for more than two decades and remains in routine clinical use.^[7] Not approved in the United States domperidone is not an FDA-approved drug for any use; the only legal route to obtain it there is for the treating physician to file an Investigational New Drug (IND) expanded-access application directly with the FDA for a specific patient with a severe gastrointestinal condition.^[9] This is a genuinely important cross-border access difference for any pharmacist working with patients, prescribers, or literature that assumes US availability. Cardiac safety: Health Canada's 2015 advisory caps domperidone at a maximum recommended dose of 30 mg/day, at the lowest effective dose for the shortest possible duration, and specifically contraindicates it in patients with prolonged cardiac conduction intervals (particularly QT), significant electrolyte disturbance, cardiac disease such as congestive heart failure, moderate or severe hepatic impairment, or concomitant use of a QT-prolonging drug or a potent CYP3A4 inhibitor.^[7] Consider a cardiac assessment, including an ECG, before starting and during treatment in patients at higher risk for QT prolongation or arrhythmia — age over 60 and doses above 30 mg/day are specifically flagged as higher-risk.^[7] Dose: 10 mg orally, up to 3 times daily (maximum 30 mg/day total), 15-30 minutes before meals.

Erythromycin — a genuinely short-term prokinetic

Erythromycin is a motilin-receptor agonist and a genuinely effective accelerator of gastric emptying, but oral use develops tachyphylaxis within days to a few weeks as motilin receptors down-regulate — this is why it is used short-term (days to a few weeks) rather than as chronic maintenance therapy.^[1] Oral dose: 125-250 mg 3 times daily before meals, for a short, defined course. IV dose (acute/inpatient use, or periprocedural reversal of a GLP-1-related emptying delay): approximately 3 mg/kg. A systematic review and network meta-analysis of macrolide use spanning 33 studies and data on 22.6 million subjects found no association between macrolide use and arrhythmia or cardiovascular mortality, though the usual caution around combining it with other QT-prolonging drugs still applies given erythromycin's own, separately established QT effect.^[1]

Antiemetics — symptom relief without changing gastric emptying

Adjunct, not disease-modifying antiemetic agents (ondansetron, dimenhydrinate, prochlorperazine) are suggested for improved symptom control, but current evidence is explicit that these medications do not improve gastric emptying itself (conditional recommendation, low-quality evidence) — they treat the symptom, not the underlying motility disorder, and should be framed to the patient that way.^[1]

GLP-1 receptor agonists — recognize, don't just treat around

Because GLP-1 receptor agonists and tirzepatide slow gastric emptying by design, a patient on one of these drugs who develops gastroparesis-type symptoms needs the drug itself reviewed as a possible cause or aggravating factor, in partnership with the prescriber, before simply adding a prokinetic on top of it.^[6][5] Symptom presence or absence cannot be used to reliably diagnose or exclude delayed gastric emptying in a patient on one of these drugs — objective testing is still required if genuinely needed.^[6] A related periprocedural point worth knowing: retained gastric contents at endoscopy are roughly four-fold more common in GLP-1 users (13.6% versus 2.3% in one large series), though aspiration itself remains rare (about 0.2% of those with retained contents); IV erythromycin (about 3 mg/kg) can help reverse the GLP-1-related emptying delay before an urgent procedure.^[6]

Therapies current evidence specifically does NOT support

Central neuromodulators not recommended for management of gastroparesis (strong recommendation, moderate-quality evidence) — a placebo-controlled trial of nortriptyline in idiopathic gastroparesis showed no benefit over placebo on the primary symptom outcome.^[1] Ghrelin receptor agonists current data do not support use for management of gastroparesis (strong recommendation, moderate-quality evidence).^[1] Haloperidol current data do not support use for treatment of gastroparesis (conditional recommendation, low-quality evidence), notwithstanding some observational emergency-department experience.^[1] Intrapyloric botulinum toxin injection not recommended for patients with gastroparesis, based on randomized controlled trials (strong recommendation, moderate-quality evidence) — despite a biologically plausible pyloric-relaxation mechanism, it has not shown benefit over sham injection.^[1]

Refractory disease — legitimate next steps, not "nothing more to offer"

For patients whose symptoms remain refractory to medical therapy, current guidance suggests pyloromyotomy (including gastric per-oral endoscopic myotomy, G-POEM) over no treatment for symptom control (conditional recommendation, low-quality evidence), and gastric electrical stimulation may be considered as a humanitarian-use device for symptom control, particularly for nausea and vomiting (conditional recommendation, low-quality evidence).^[1] These are specialist-managed, surgical/gastroenterology-referral decisions — the pharmacist's role is recognizing when a patient has genuinely reached this point and ensuring referral happens rather than cycling through additional unsupported drug therapy.

• Small particle diet is first-line, guideline-recommended dietary management — it increases the likelihood of symptom relief and measurably enhances gastric emptying compared with a regular-texture diet (conditional recommendation, low-quality evidence).^[1]
• Low-fat content — fat slows gastric emptying physiologically, independent of any underlying motility disorder.
• Low insoluble/non-digestible fibre — poorly digestible fibre empties even more slowly than other solids and is a recognized contributor to bezoar formation in a stomach that already empties slowly.
• Smaller, more frequent meals (4-5 small meals a day rather than 2-3 large ones) reduce the volume the stomach needs to process at any one time.
• For more severe disease, shift a larger proportion of calories to liquid or blenderized form — liquids empty through a gastric mechanism that is far less dependent on the antral grinding and coordinated motility that gastroparesis disrupts.
• Follow a stepwise nutrition ladder when oral intake alone is not adequate: oral dietary modification first, then enteral nutrition via a jejunal (post-pyloric) feeding route in preference to a purely gastric feeding tube — since gastric feeds still have to transit the same dysfunctional stomach — and parenteral nutrition only when enteral routes genuinely cannot meet nutritional needs.^[1]
• Review the medication list specifically for opioids, anticholinergic drugs, and GLP-1 receptor agonists/tirzepatide that may be causing or worsening symptoms, and pursue deprescribing or substitution in partnership with the prescriber wherever feasible.^[5]
• In diabetic gastroparesis, work with the patient's diabetes care team to optimize glycemic control — this is itself a non-pharmacologic-adjacent intervention with genuine disease-modifying potential given the bidirectional relationship between hyperglycemia and delayed emptying.^[5][1]

Diabetic gastroparesis

The relationship between glycemic control and gastroparesis runs in both directions: chronic hyperglycemia is a cause of diabetic gastroparesis through vagal and enteric neuropathy, and acute hyperglycemia independently slows gastric emptying and can worsen symptoms in the short term, even in a patient whose long-term control is reasonable.^[5][1] Diabetes Canada's own neuropathy guideline suggests optimal glucose control specifically to reduce the future risk of aggravating established gastroparesis, and names GLP-1 receptor agonists and opioids as medications worth withdrawing when they are contributing to the picture.^[5] A practical, widely taught insulin-timing point for erratic diabetic gastroparesis: because food absorption timing becomes unpredictable when gastric emptying is delayed and variable, prandial insulin dosed strictly before the meal can mismatch the eventual absorption of that meal — discuss individualized prandial insulin timing (including dosing after eating, once the amount actually tolerated is known) with the patient's diabetes care team rather than leaving a fixed pre-meal regimen unexamined.

Patients on a GLP-1 receptor agonist or tirzepatide

Review the GLP-1 receptor agonist or tirzepatide itself as a possible cause or aggravating factor before adding a prokinetic on top of it, in partnership with the prescriber.^[6] Symptoms alone cannot reliably confirm or exclude delayed gastric emptying in this population — objective testing is still needed if the diagnosis genuinely needs to be established.^[6] Flag any upcoming endoscopy or procedure requiring sedation, since retained gastric contents are meaningfully more common in GLP-1 users and periprocedural planning (extended fasting, or periprocedural IV erythromycin) may be needed.^[6]

Older adults

Health Canada's own metoclopramide advisory specifically flags the elderly, and especially elderly women, as being at increased risk of tardive dyskinesia — use particular caution, favour the lowest effective dose, and hold to the 12-week ceiling more strictly in this group.^[2] Domperidone's cardiac risk is also specifically elevated in patients over 60; a baseline and on-treatment ECG is worth considering more readily in this group.^[7]

Renal and hepatic impairment

Domperidone is specifically contraindicated in moderate or severe hepatic impairment per Health Canada's advisory, given reduced clearance and consequent higher systemic exposure raising cardiac risk.^[7] Dose-adjust metoclopramide and erythromycin in significant renal impairment; consult a renal dosing reference or pharmacist for the specific adjustment.

Pregnancy

Metoclopramide has a longer and more established history of use in pregnancy, including for hyperemesis gravidarum, than domperidone does; involve obstetrics in any pharmacologic decision for gastroparesis symptoms in pregnancy, and reassess the diagnosis carefully given how much normal gastrointestinal symptomatology overlaps with pregnancy itself.

Post-surgical patients

Vagal-injury-related gastroparesis following fundoplication, vagotomy, or bariatric surgery is best managed in coordination with the original surgical team; nutritional strategy (see Non-Pharmacologic Management) often carries more of the therapeutic weight here than pharmacotherapy, and revisional surgery decisions belong with the surgical/gastroenterology team, not primary pharmacotherapy escalation alone.

• Reassess symptom burden and nutritional status/weight trend at every follow-up — a plan that was adequate at diagnosis may not remain adequate as the disease or a comorbidity progresses.
• For every patient on metoclopramide: screen specifically for early involuntary-movement signs at each visit or refill, and treat reaching the 12-week mark as a scheduled decision point requiring an explicit, documented risk-benefit reassessment — not a default continuation.^[2]
• For every patient on domperidone: reassess cardiac risk factors and the full medication list for new QT-prolonging drugs or potent CYP3A4 inhibitors at each review, and repeat ECG assessment when risk factors change, not only at initiation.^[7]
• In diabetic gastroparesis, track glycemic control trend alongside symptom control, given the bidirectional relationship between the two.^[5][1]
• Reassess for bezoar or obstruction red flags at every visit, particularly in a patient who has not been strictly following the low-fibre dietary guidance.
• For a patient on a GLP-1 receptor agonist or tirzepatide, reassess whether the drug remains necessary at its current dose and whether symptoms have changed with any dose adjustment made by the prescribing team.^[6]

1. Dietary modification alone insufficient: review adherence to the small-particle, low-fat, low-fibre, small-frequent-meal pattern before assuming it has failed outright.^[1]
2. Persistent symptoms despite adequate dietary trial: review and address reversible contributors first — opioids, anticholinergic drugs, GLP-1 receptor agonists/tirzepatide, and, in diabetic gastroparesis, suboptimal glycemic control — before adding a prokinetic on top of an unaddressed cause.^[5][6]
3. Still symptomatic: add a single prokinetic — metoclopramide (lowest effective dose, 12-week ceiling, documented counseling) or, where available, domperidone (maximum 30 mg/day, cardiac risk assessed) — rather than starting both simultaneously.^[1][2][7]
4. Inadequate response or intolerance to the first prokinetic: consider a short, defined course of erythromycin for acute symptom control, recognizing tachyphylaxis will limit its usefulness beyond a few weeks, rather than escalating the dose of an already-maximized agent.^[1]
5. Genuinely refractory to medical therapy after the above steps: refer for evaluation for pyloromyotomy (including G-POEM) or gastric electrical stimulation rather than reaching for central neuromodulators, ghrelin agonists, haloperidol, or intrapyloric botulinum toxin — none of which current evidence supports.^[1]
6. Nutritional decline (weight loss, dehydration) at any point in this ladder: escalate nutritional support proactively — enteral (preferably jejunal) before parenteral — rather than waiting for malnutrition to become clinically obvious.^[1]
7. Any new finding suggesting mechanical obstruction was missed, or a suspected bezoar: stop and re-investigate before continuing empiric gastroparesis management on the existing diagnosis.^[1]

• Diagnosing or treating gastroparesis without having genuinely excluded mechanical obstruction first.^[1]
• Performing gastric emptying scintigraphy while blood glucose is acutely elevated, producing a falsely delayed result that reflects the moment's hyperglycemia rather than true underlying disease.^[1][8]
• Continuing metoclopramide past 12 weeks by default, without a documented, deliberate risk-benefit reassessment.^[2]
• Missing early tardive dyskinesia signs because they were never specifically screened for at follow-up or at refill.^[2]
• Prescribing domperidone without checking baseline cardiac risk factors or QT-prolonging co-medications, or exceeding the 30 mg/day maximum.^[7]
• Assuming a patient or prescriber outside Canada can access domperidone the same way — in the US it requires an individual FDA IND expanded-access application, not a routine prescription.^[9]
• Continuing erythromycin as fixed, chronic maintenance therapy and expecting sustained benefit despite the well-documented tachyphylaxis.^[1]
• Reaching for central neuromodulators, ghrelin agonists, haloperidol, or intrapyloric botulinum toxin as routine gastroparesis therapy, despite current evidence specifically not supporting any of them.^[1]
• Missing a GLP-1 receptor agonist or tirzepatide as a contributing or unmasking cause of new gastroparesis-type symptoms.^[6][5]
• Relying on symptoms alone to diagnose or exclude delayed gastric emptying in a patient taking a GLP-1 receptor agonist.^[6]
• Treating retained gastric food seen incidentally at endoscopy as automatically diagnostic of gastroparesis without considering confounding medications or risk factors.^[1]

How to use this table: Doses are adult doses and require patient-specific confirmation (renal/hepatic function, weight, allergy history). Pediatric dosing is weight-based per the current product monograph unless stated. Drug pricing is intentionally omitted. Select any drug name to open its complete Pharmasist Drug Database page.

The Only Approved Prokinetic — Metoclopramide

Health Canada: avoid use beyond 12 weeks unless the benefit is judged to outweigh the tardive dyskinesia risk. Counsel every patient on early movement-disorder signs before the first dose and screen for them at every visit or refill.

Domperidone — Canada-Specific Access and Cardiac Safety

Approved and prescribable in Canada; not FDA-approved in the US, where access requires an individual Investigational New Drug expanded-access application to the FDA. Maximum 30 mg/day per Health Canada's 2015 advisory.

Erythromycin — Short-Term Motilin-Agonist Prokinetic

Genuinely effective at accelerating gastric emptying, but oral tachyphylaxis develops within days to a few weeks via motilin-receptor down-regulation — not for chronic maintenance use.

Antiemetics for Symptom Control — Do Not Improve Gastric Emptying

Suggested for symptom relief, but current evidence is explicit that none of these agents improves gastric emptying itself — frame them to the patient as symptomatic, not disease-modifying, therapy.

Other Prokinetics Used Off-Label

Not specifically approved for gastroparesis in Canada or the US; used off-label based on low-quality trial evidence when first-line options are inadequate or not tolerated.

Not Recommended for Gastroparesis Despite Plausible Mechanisms

Each carries a biologically plausible rationale that has not held up in controlled evidence — avoid reaching for any of these simply because a patient remains symptomatic on first-line therapy.

Medications That Cause or Worsen Delayed Gastric Emptying — Review for Deprescribing or Substitution

None of these are contraindicated outright, but each is worth a specific second look whenever gastroparesis symptoms are new, worsening, or hard to control.