Loperamide Stats & Data
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DrugBankDescription
One of the long-acting synthetic antidiarrheals; it is not significantly absorbed from the gut, and has no effect on the adrenergic system or central nervous system, but may antagonize histamine and interfere with acetylcholine release locally.
Mechanism of Action
<i>In vitro</i> and animal studies show that Loperamide acts by slowing intestinal motility and by affecting water and electrolyte movement through the bowel. Loperamide inhibits peristaltic activity by a direct effect on the circular and longitudinal muscles of the intestinal wall. It is a non-selective calcium channel blocker and binds to opioid mu-receptors. Evidence also suggests that at higher concentrations it binds to calmodulin.
Pharmacodynamics
Loperamide is a synthetic anti-diarrheal indicated for the control and symptomatic relief of acute nonspecific diarrhea and of chronic diarrhea associated with inflammatory bowel disease. Loperamide is also indicated for reducing the volume of discharge from ileostomies. In man, Loperamide prolongs the transit time of the intestinal contents. It reduces the daily fecal volume, increases the viscosity and bulk density, and diminishes the loss of fluid and electrolytes. Tolerance to the antidiarrheal effect has not been observed. Loperamide is an opioid receptor agonist and acts on the mu opioid receptors in the myenteric plexus large intestines; it does not affect the central nervous system like other opioids. It works specifically by decreasing the activity of the myenteric plexus which decreases the motility of the circular and longitudinal smooth muscles of the intestinal wall. This increases the amount of time substances stay in the intestine, allowing for more water to be absorbed out of the fecal matter. Loperamide also decreases colonic mass movements and suppresses the gastrocolic reflex.
Absorption
Not significantly absorbed from the gut
Indication
For the control and symptomatic relief of acute nonspecific diarrhea and of chronic diarrhea associated with inflammatory bowel disease or gastroenteritis. Also used for reducing the volume of discharge from ileostomies.
Elimination
Excretion of the unchanged loperamide and its metabolites mainly occurs through the feces.
Measured Affinities
Guide to PHARMACOLOGYMeasured binding and functional data for loperamide, curated by the IUPHAR/BPS Guide to PHARMACOLOGY. Each row cites the paper it came from. Lower concentrations mean tighter binding — a value in the sub-nanomolar range indicates a very potent interaction.
| Target | Action | Measure | Value | Concentration | Species | Source |
|---|---|---|---|---|---|---|
| μ receptor OPRM1 | Agonist | pKi | 9.28 | 0.525 nM | Human | PMID 15454210 |
Reading this. pKi, pEC50 and pIC50 are negative log molar values, so a higher number means a tighter interaction; the concentration column converts them for you. Values from non-human species are laboratory measurements and do not translate directly to human effect. Receptor affinity is not a dose — it describes what a molecule binds, not how much of it is safe to take.
Receptor data from the IUPHAR/BPS Guide to PHARMACOLOGY (v2026.2), licensed CC BY-SA 4.0. Matched to this substance by InChIKey.
Loperamide is an over-the-counter antidiarrheal with mu-opioid agonist activity. Central nervous system opioid effects are not observed after therapeutic oral dosing because of poor bioavailability and minimal central nervous system penetration. When loperamide is taken in large doses or with other drugs that may alter its pharmacokinetic effects, such as p-glycoprotein inhibitors, loperamide produces opioid-like symptoms. These include a sensation of euphoria, miosis, central nervous system depression, and respiratory depression.
Toxicity (DrugBank)
Oral, mouse: LD50 = 105 mg/kg. Symptoms of overdose include constipation, drowsiness, lethargy, and nausea.
Experience Report Analysis
ErowidDemographics
Gender Distribution
Age Distribution
Reports Over Time
Effect Analysis
ErowidEffects aggregated from 16 experience reports (16 single-substance Erowid)
Effect Sentiment Distribution
Confidence Distribution
Each bar is the share of reports mentioning the effect; its whisker, and the band on the rows below, is the 95% interval: where the share could plausibly be with other reports of the same kind.
Too few reports for bars: these effects come from 16 single-substance Erowid reports, and a bar is drawn only from 20 reports or more. With fewer, a percentage cannot tell a common effect from a rare one. Counts are shown instead. Why 20?
Positive Effects 2
Adverse Effects 1
Show 1 neutral or unclassified mention
Also reported in combinations. In the 11 Loperamide reports where another drug was taken too, 2 mention hospital, emergency services or an overdose, 1 a seizure and 0 psychosis (too few reports for percentages). In the 16 single-substance reports: 2, 0 and 0. These are not in the figures above: they cannot be put down to Loperamide alone, and a mention is not always something that happened to the writer.
Dosage Distribution
Dose distribution from experience reports, one dose per report (the first listed). Doses above Q3 + 3×IQR, far above what people typically take, are left out of the median and range and listed under each route: most are real heavy doses or overdoses, not mistakes.
Real-World Dose Distribution
ErowidFrom 33 of 37 recorded dose entries: those that state a weight (mg, g or µg), in routes with at least five of them. Values above Q3 + 3×IQR, far above what people typically take, are left out; they can include real heavy doses and overdoses, not only mistakes.
Oral (n=33)
Form / Preparation
Most common forms and preparations, as a share of the 21 reports that give one; whiskers are 95% intervals
Body-Weight Dosing
Dose per kg of body weight, one dose per report (the first listed), from reports giving a weight of 30–250 kg. Doses above Q3 + 3×IQR, far above what people typically take, are left out of the median and range and listed under each route.
Redose Patterns
Redosing behavior across 21 reports