BSN Tracker

loperamide

Brand: Imodium

Prototype Drug
Drug Class: antidiarrheal
Drug Family: GI agent
Subclass: peripheral mu opioid receptor agonist
Organ Systems: gastrointestinal

Mechanism of Action

Peripheral mu opioid agonist that does not cross BBB at therapeutic doses; reduces intestinal motility, increases anal sphincter tone, reduces intestinal secretions.

mu opioid receptor (GI, peripheral)

Indications

  • acute diarrhea (non-infectious)
  • chronic diarrhea (IBD, ileostomy)
  • traveler's diarrhea

Contraindications

  • diarrhea caused by invasive organisms (bloody diarrhea)
  • C. difficile diarrhea
  • ulcerative colitis (toxic megacolon risk)
  • children under 2

Adverse Effects

Common

  • constipation
  • dizziness
  • nausea
  • abdominal cramping

Serious

  • toxic megacolon
  • cardiac arrhythmias and death (at supra-therapeutic doses — opioid-like CNS effects)

Pharmacokinetics (ADME)

Absorption ~40% absorbed
Distribution large Vd
Metabolism extensive hepatic CYP2C8, CYP3A4
Excretion fecal
Half-life 10-14 hours
Onset 1-3 hours
Peak 2-4 hours
Duration variable
Protein Binding 97%
Vd large

Drug Interactions

Drug / Agent Mechanism Severity
P-gp inhibitors (quinidine) increases loperamide CNS penetration — risk of CNS opioid effects major
CYP3A4 inhibitors increases loperamide exposure moderate

Nursing Considerations

  1. Maximum dose: 16 mg/day OTC; 8 mg/day per episode (misuse risk at higher doses)
  2. AVOID in bloody diarrhea (may worsen invasive infection by slowing bacterial clearance)
  3. AVOID in C. diff colitis (toxic megacolon risk)
  4. High-dose misuse: FDA warning — cardiac arrhythmias (QT prolongation) at supra-therapeutic doses

Clinical Pearls

  • P-gp normally limits CNS penetration of loperamide; P-gp inhibitors (quinidine) allow CNS entry causing euphoria/CNS effects — abuse potential
  • FDA QT warning: supra-therapeutic doses (misuse) can cause life-threatening arrhythmias and cardiac arrest

Safety Profile

Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Not required
Hepatic Adjustment Required
TDM Not required

Concordance Terms

Cross-referenced clinical concepts — click any term to see all content where it appears.

Acute Diarrhea (non-infectious) Antidiarrheal Chronic Diarrhea (IBD, Ileostomy) Traveler's Diarrhea
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