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Loperamide HCl

1. Generic & Brand Names

  • Generic: Loperamide HCl

  • Brands: Imodium® (global), Diamode®, Loperacap®

  • Combinations: Imodium® Plus (with simethicone)

  • Formulations:

    • Capsules/Tablets (2mg)

    • Liquid (1mg/5mL, 1mg/7.5mL)

    • Chewable tablets

  • OTC Availability: Yes (restricted in some countries)

2. Drug Class & Mechanism

  • Class: Opioid Receptor Agonist (peripherally acting)

  • Mechanism:

    • Binds μ-opioid receptors in the intestinal wall → ↓ peristalsis, ↑ transit time

    • ↑ Anal sphincter tone → reduces urgency/frequency

    • No CNS effects at standard doses (doesn't cross BBB)

3. FDA-Approved Uses

IndicationDetails
Acute DiarrheaAdults & children ≥6 years
Chronic DiarrheaIBS-D, IBD maintenance (off-label)
Traveler's DiarrheaFirst-line with antibiotics

4. Dosing Regimens

GroupInitial DoseMaintenanceMax Daily
Adults4 mg (2 tabs)2 mg after each loose stool8 mg/day*
Children 9-11 yrs2 mg1 mg after each loose stool6 mg/day
Children 6-8 yrs2 mg1 mg after each loose stool4 mg/day

* FDA Limit: 8 mg/24h OTC; 16 mg/24h Rx (with restrictions)
Never use in children <6 years (respiratory depression risk)

5. Black Box Warning (FDA 2019)

  • Cardiac Risks:

    • QT prolongation → Torsades de Pointes

    • Fatal arrhythmias reported with doses >16 mg/day

  • Abuse Potential:

    • Used to achieve opioid "high" (requires 50-100+ mg)

    • Causes euphoria when combined with CYP inhibitors

6. Side Effects

Common (≥5%)Serious (Require Discontinuation)
ConstipationToxic Megacolon (IBD patients)
DizzinessParalytic Ileus
NauseaQT Prolongation → Cardiac Arrest
Abdominal painHypersensitivity Reactions

7. Absolute Contraindications

  • Bloody diarrhea (may worsen C. diff/invasive pathogens)

  • Fever >101.3°F (38.5°C)

  • Ulcerative colitis/C. diff infection

  • Concomitant QT-prolonging drugs (amiodarone, macrolides)

8. Critical Drug Interactions

MedicationRisk
CYP3A4 Inhibitors↑ Loperamide levels 3-4x → ↑ toxicity (e.g., ritonavir, grapefruit)
CYP2C8 InhibitorsGemfibrozil → ↑ levels 2-3x
Opioids↑ CNS depression

9. Abuse-Deterrent Formulations

  • Imodium® Advanced (EU): Added naloxone (blocks opioid receptors if crushed/injected)

  • US Restrictions:

    • Blister packaging (max 12 capsules per pack)

    • Behind-counter sales in some states

10. When to Seek Medical Help

Stop loperamide and consult MD immediately if:

  • Diarrhea >48 hours

  • Blood/mucus in stool

  • Fever or severe abdominal pain

  • Dizziness/fainting (cardiac warning)

Clinical Alternatives

ScenarioSafer Alternatives
Mild DiarrheaBismuth subsalicylate (Pepto-Bismol®)
IBS-DEluxadoline, Rifaximin
C. diffVancomycin, Fidaxomicin

Patient Counseling

  1. "Never exceed maximum dose – 8 mg/day OTC."

  2. "Discontinue if no improvement in 24h – may indicate infection."

  3. "Avoid with grapefruit juice – increases toxicity risk."

  4. "Seek ER for:

    • Fast/irregular heartbeat

    • Severe constipation/abdominal swelling

    • Bloody stools"

⚠️ Red Flag: Combining loperamide with ketoconazole or ritonavir has caused fatal arrhythmias at therapeutic doses.

Prescribing Status: OTC with purchase limits; Rx for chronic conditions (max 16 mg/day with ECG monitoring).
Global Status: Restricted to Rx-only in France, Japan, and parts of the Middle East.

Sources: FDA Drug Safety Communication (2019), EMA Review (2018), Clin Gastroenterol Hepatol.

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