Motilin
Also known as: MLN, motilin peptide, human motilin, gastrointestinal motility peptide, 22-amino-acid motilin
Endogenous gastrointestinal peptide hormone — 22-amino-acid polypeptide; migrating motor complex (MMC) regulator; motilin receptor (MLNR/GPR38) ligand
What it is
Motilin is a gut hormone that anyone with delayed gastric emptying (gastroparesis), chronic nausea, or feeding difficulties in hospital care may encounter. Researchers study it because it controls the stomach's powerful fasting contractions and signals hunger to the brain. It is also the natural target of erythromycin-based prokinetic drugs.
The scientific side
motilin is a 22-amino-acid peptide hormone produced by endocrine M-cells in the mucosa of the upper small intestine, primarily the duodenum and jejunum. It is the primary endogenous ligand for the motilin receptor (MLNR, also called GPR38), a G protein-coupled receptor expressed in gastrointestinal smooth muscle, enteric neurons, and selected brain regions. During fasting, plasma motilin levels cycle with the interdigestive migrating motor complex (MMC), rising approximately every 90–120 minutes to trigger forceful phase III gastric contractions that sweep undigested material distally — historically called the 'gastrointestinal housekeeper.' These contractions are absent in rodents, whose motilin and MLNR genes are pseudogenes, limiting rodent-based research. Human studies demonstrate that motilin-induced phase III contractions of the gastric antrum coincide with subjective hunger peaks. Elevated motilin in obese patients is paradoxically associated with blunted hunger responses due to a shift in phase III origin from antrum to duodenum; Roux-en-Y gastric bypass surgery normalizes this by reducing elevated plasma motilin and restoring hunger signaling. Motilin receptor agonists such as erythromycin and the selective non-macrolide camicinal (GSK962040) replicate these prokinetic effects pharmacologically. Camicinal at 150 mg induced gastric phase III contractions within 34 minutes versus 18 hours with placebo in healthy volunteers, and a single 125 mg dose reduced gastric half-emptying time by 65% in type 1 diabetic patients with gastroparesis (PMIDs: 28782145, 26924243). Beyond the gut, motilin receptors in the basolateral amygdala on GABAergic interneurons mediate depolarization, facilitated inhibitory transmission, and reduced anxiety-like behavior in preclinical models — a CNS role relevant to gut-brain axis disorders. Elevated circulating motilin in diabetic individuals after acute pancreatitis correlates with glycemic dysregulation and gastroparetic symptoms, positioning it as a disease biomarker. The concept of 'biased agonism' at the motilin receptor — different agonists preferentially activating distinct intracellular pathways — is proposed for developing next-generation prokinetics that avoid tachyphylaxis.
Class: Endogenous gastrointestinal peptide hormone — 22-amino-acid polypeptide; migrating motor complex (MMC) regulator; motilin receptor (MLNR/GPR38) ligand
Administration & storage
- Administration
- Intravenous infusion of erythromycin (40–250 mg in saline) — used in research and clinical pre-endoscopy protocols as a motilin receptor agonist surrogateIntravenous infusion of synthetic motilin peptide — used in controlled research settings onlynot clinically availableEnteral/nasogastric administration of camicinal 50 mg — used in ICU feed intolerance studies
- Storage
- Synthetic motilin peptide for research: store lyophilized powder at -20°C protected from light and moisture; reconstituted solutions should be used immediately or aliquoted and stored at -80°C. Erythromycin IV preparations: store per manufacturer specifications, typically at room temperature protected from light. Camicinal is investigational and not commercially available.
- Cautions
- Erythromycin (primary clinical motilin receptor agonist): risk of QTc prolongation — do not use in patients with long QT syndrome, hypokalemia, hypomagnesemia, or concurrent QT-prolonging medications. ECG monitoring required in at-risk patients.,Antibiotic selection pressure: clinical use of erythromycin as a prokinetic carries the risk of promoting macrolide-resistant bacterial strains; this risk must be weighed against prokinetic benefit, particularly in repeated dosing or ICU settings.,Tachyphylaxis: erythromycin loses prokinetic efficacy with repeated dosing due to motilin receptor downregulation; this is a well-documented limitation and a primary driver for developing next-generation motilin agonists such as camicinal.,No approved motilin peptide product: motilin itself is not an approved drug — individuals seeking motilin-based effects should be aware that only erythromycin (off-label) has substantial human trial data, and investigational selective agonists are not approved for clinical use.,Drug interactions: erythromycin is a potent CYP3A4 inhibitor — significant pharmacokinetic interactions exist with statins (rhabdomyolysis risk), anticoagulants, immunosuppressants, and numerous other medications.
Legal & regulatory status
Motilin itself is not FDA-approved as a drug. Its pharmacology is clinically exploited through motilin receptor agonists: erythromycin (FDA-approved antibiotic used off-label as a prokinetic via motilin receptor…
Motilin is not listed on the WADA Prohibited List (2024). It is an endogenous peptide hormone that does not appear on any current anti-doping prohibited substances schedule. Motilin receptor agonists such as…
Motilin as a peptide entity is not approved by Health Canada as a therapeutic drug. Erythromycin is approved in Canada for its antibiotic indications; its prokinetic off-label use via motilin receptor agonism is…
What it's studied for
- Gastroparesis — delayed gastric emptying in type 1 diabetes mellitus Phase II RCT
- Feed intolerance in critically ill mechanically ventilated patients Human RCT
- Pre-endoscopy gastric emptying in acute upper gastrointestinal haemorrhage Mixed
- Hunger and food intake regulation — motilin as an orexigenic gut-brain signal Human RCT
- Motilin-induced gastric motility and MMC characterization — Phase I pharmacodynamics of novel motilin agonists Human RCT
- Obesity and post-bariatric surgery — motilin as a hunger biomarker and surgical target Human observational
- Diabetic post-pancreatitis gastrointestinal motility dysfunction — motilin as a biomarker Human observational
- Anxiety and CNS gut-brain axis — preclinical anxiolytic effects of motilin receptor activation Animal studies only
- Systemic sclerosis (scleroderma) gastrointestinal dysmotility — motilin modulation by neuromodulation Human observational
Safety signals
- QTc interval prolongation (erythromycin as motilin agonist)
- Tachyphylaxis (loss of prokinetic efficacy with repeated dosing)
- Gastrointestinal adverse effects (nausea, cramping, diarrhea) with motilin receptor agonists
- CYP3A4-mediated drug interactions (erythromycin)
- Antibiotic resistance promotion with erythromycin as prokinetic
- Dysregulated hunger signaling and feeding behavior — elevated endogenous motilin in pathological states
- Species-dependent pharmacology and absence of rodent motilin system limiting translational research
All studies (8)
Frequently asked
Can I take a motilin supplement or injection to help my gastroparesis?
Motilin is not available as an approved supplement or injectable drug. The most studied clinical approach to activating motilin receptors is intravenous erythromycin (an antibiotic that acts as a motilin receptor agonist), which is used off-label by clinicians in hospital settings. Investigational selective motilin agonists like camicinal showed promise in Phase 2 trials but are not commercially available. Any approach to gastroparesis treatment should be managed by a gastroenterologist. Self-administering unprescribed research chemicals that claim to target motilin receptors carries significant safety risks.
Does erythromycin work long-term as a prokinetic for gastroparesis?
Erythromycin is effective short-term for triggering gastric contractions via motilin receptor agonism, but it loses efficacy with repeated dosing due to motilin receptor desensitization (tachyphylaxis). This is a well-documented limitation. It is generally used for acute settings (such as pre-endoscopy gastric emptying) rather than chronic gastroparesis management. Speak with your gastroenterologist about alternative options and the risks of prolonged antibiotic use.
Is motilin related to hunger? Can it help with appetite or weight loss?
Motilin plays a genuine role in signaling hunger during fasting — its peak release triggers gastric contractions that the brain interprets as hunger. Human studies show that activating motilin receptors increases food intake and hedonic appetite. This makes it unlikely to be useful as a weight loss tool; in fact, in obesity, motilin levels are already elevated. The motilin system is an area of active research for understanding hunger regulation rather than a therapeutic target for appetite suppression.
What is the motilin receptor and are any drugs specifically targeting it approved?
The motilin receptor (MLNR, also called GPR38) is a G protein-coupled receptor found in gastrointestinal smooth muscle, enteric nerves, and select brain regions. It is activated by the endogenous hormone motilin and by the macrolide antibiotic erythromycin. Several selective non-antibiotic motilin receptor agonists (camicinal/GSK962040, DS-3801b) have completed Phase 1–2 clinical trials with promising results but have not yet received regulatory approval. As of now, no drug is specifically FDA-approved for motilin receptor agonism as a labeled indication.
Why can't researchers study motilin in rats and mice?
Both the motilin gene and the motilin receptor gene are non-functional pseudogenes in rodents including rats and mice, meaning these species have no active motilin system. This is a major barrier to preclinical research: standard rodent models cannot be used to study motilin's physiological roles or to test motilin receptor agonists. Researchers use alternative species (house musk shrews, dogs, transgenic mice expressing the human motilin receptor) to investigate motilin biology. This species gap is one reason why translating motilin receptor drug research from bench to clinical trials has been challenging.