Drug reference

Loperamide

Peripherally-acting mu-opioid receptor agonist (antidiarrheal) · Antidiarrheal

Also known as Loperamide Hydrochloride, Imodium

START

Rule out infectious/bloody diarrhea (contraindicated). Ensure adequate hydration. Do NOT use as sole therapy in dysentery or C. difficile.

TYPICAL MAX

16mg/day (adults). Do not exceed—high-dose misuse can cause fatal cardiac arrhythmias (QT prolongation, torsades de pointes).

STOP IF

Bloody diarrhea, fever, abdominal distension, constipation >48 hours, signs of C. difficile, symptoms persisting >48 hours.

WATCH

Never use in acute colitis or C. difficile (risk of toxic megacolon). Cardiac toxicity at high doses (>16mg) or in CYP2D6 poor metabolizers. FDA black box warning for serious cardiac events with high doses.

CDSCO approvedOTCJan AushadhiATC A07DA03

Dose laddermg/d

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 1h · Onset within 1 hour
PEAK: 3.5h · Tmax 2.5-5 hours
t½: 11h · t½ ~10.8 hours
DURATION: 12h · 10-14 hours

EXCRETION

Fecal as metabolites (~40%)

route + CYP

INTERACTIONS

12 major

incl. contraindicated

PREGNANCY

Limited data; minimal systemic absorption suggests low risk. Use only if clearly needed—prefer dietary measures and hydration first.

FDA category + note

Top interactionssee all 12 →

C Difficile InfectionContraindicatedDatabaseKimi deep-research + Cla
AbirateroneSevereDatabaseDDInter
AmiodaroneSevereDatabaseDDInter
AmprenavirSevereDatabaseDDInter

Available in India

85 branded formulations and 6 fixed-dose combinations. Look up specific brands in the Drugs workspace.

Jan Aushadhi — generic available at GoI pharmacies

Mechanism

Binds to mu-opioid receptors on myenteric plexus of intestinal wall, inhibiting acetylcholine and prostaglandin release, reducing peristalsis, increasing intestinal transit time, and enhancing water and electrolyte absorption. Poor CNS penetration due to P-gp efflux—minimal opioid CNS effects at therapeutic doses.

Indications

Acute diarrhea (non-infectious, adjunctive)Chronic diarrhea (IBS-D, inflammatory bowel disease—adjunctive)Travelers' diarrhea (adjunctive to antibiotics)Fecal incontinenceIleostomy output reduction

Dosing

Adult: Acute diarrhea: 4mg PO initially, then 2mg after each loose stool; max 16mg/day (OTC) or 8mg/day (some regions). Chronic diarrhea: 4-8mg/day in divided doses; max 16mg/day.
Pediatric: ≥2 years: 0.08-0.24mg/kg/day divided BID-TID (max 2mg/dose, 6mg/day for 2-5 years; max 8mg/day for 6-12 years).
Renal adjustment: No adjustment needed (minimal renal excretion, poor bioavailability).
Hepatic adjustment: Use caution in severe hepatic impairment (reduced first-pass metabolism may increase levels).
Geriatric: No specific adjustment; increased risk of constipation and ileus.
Max dose: 16mg/day (adults); 8mg/day (children 6-12 years); 6mg/day (children 2-5 years)

Pharmacokinetics

Onset

Antidiarrheal effect within 1 hour

Peak effect

Tmax 2.5-5 hours (capsule); 1.6-2.8 hours (liquid)

Duration

10-14 hours per dose

Half-life

~10.8 hours (range 9.1-14.4h); longer with hepatic impairment

Bioavailability

~40% (extensive first-pass metabolism; P-gp efflux from CNS)

Protein binding

~97%

Metabolism

Extensive hepatic via CYP3A4 and CYP2C8 to inactive N-demethylated and hydroxylated metabolites

Excretion

~30-40% fecal (unchanged + metabolites); <2% renal (unchanged)

Contraindications

Acute dysentery (bloody diarrhea with fever—may worsen infection)
Acute colitis (pseudomembranous colitis, C. difficile)
Ileus or intestinal obstruction
Hypersensitivity to loperamide
Abdominal distension without diarrhea in children

Side effects

Common

ConstipationDizzinessNauseaAbdominal cramps / bloatingDry mouth

Serious

Cardiac arrhythmias / QT prolongation / torsades de pointes (overdose/misuse)
Ileus / toxic megacolon (especially in C. difficile or IBD)
CNS depression (overdose—crosses BBB at high doses)
Respiratory depression (overdose)
Severe hypersensitivity

Pregnancy & lactation

Pregnancy

Limited data; minimal systemic absorption suggests low risk. Use only if clearly needed—prefer dietary measures and hydration first.

Lactation

Excreted in breast milk in very small amounts; infant exposure negligible. Compatible with breastfeeding per AAP.

Drug interactions

C Difficile Infection

Contraindicated

Database

Slows gut motility, increasing toxin absorption and risk of toxic megacolon.

ABSOLUTELY contraindicated in C. difficile; treat C. difficile with appropriate antibiotics first.

Source: Kimi deep-research + Cla

Abiraterone

Severe

Database

Drug interaction classified as: metabolism

Source: DDInter

Amiodarone

Severe

Database

Increased plasma concentrations of loperamide, potentially leading to enhanced opioid-like effects and CNS depression.

Monitor for signs of CNS depression. Consider reducing loperamide dose if adverse effects occur. Use with caution.

Source: DDInter

Amprenavir

Severe

Database

Drug interaction classified as: metabolism

Source: DDInter

Atazanavir

Severe

Database

Drug interaction classified as: metabolism.

Source: DDInter

Bepridil

Severe

Database

Drug interaction classified as: absorption

Source: DDInter

Boceprevir

Severe

Database

Drug interaction classified as: metabolism

Source: DDInter

Cimetidine

Severe

Database

Modestly increased plasma concentrations of loperamide, potentially leading to enhanced opioid-like effects and CNS depression, especially at higher loperamide doses.

Monitor for signs of CNS depression. Consider reducing loperamide dose if adverse effects occur. Use with caution.

Source: DDInter

Clarithromycin

Severe

Database

Increased plasma concentrations of loperamide, potentially leading to enhanced opioid-like effects and CNS depression.

Monitor for signs of CNS depression. Consider reducing loperamide dose if adverse effects occur. Use with caution.

Source: DDInter

Clopidogrel

Severe

Database

Drug interaction classified as: metabolism.