Loperamide: veterinary dose and monograph

At a glance

Drug class

Gastrointestinal

Also known as

Imodium, Eldoper, Roko

Species with doses

Dogs, Cats, Rabbits and Small mammals

General dose range

0.1–0.2 mg/kg PO q8–12h (short term) — check the species tables for the indication

Routes

PO

Last reviewed

1 October 2026

Indications

• Acute, non-infectious / secretory diarrhoea in dogs (short-term symptomatic control)
• Reduction of faecal volume/frequency where appropriate (e.g. some chronic enteropathies, adjunct)

Loperamide dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Acute non-infectious diarrhoea (short term): Papich 5e: 0.12 mg/kg PO q8–12h. Plumb’s p.740: 0.08 mg/kg PO q8h (DeNovo; Washabau); 0.1–0.2 mg/kg PO q8–12h (Willard); 0.1 mg/kg q8h for no more than 5 days (Hall & Simpson). Avoid in MDR1 (ABCB1) breeds — neurotoxicity — and in suspected infectious diarrhoea.

Cats

• Diarrhoea (short term, caution): Papich 5e and Plumb’s p.740 (Willard 2003): 0.08–0.16 mg/kg PO q12h; suspension 0.04–0.06 mg/kg q12h (Tams). Opioid antidiarrhoeals are controversial in cats — may cause excitement.

Rabbits

• Diarrhoea: Plumb’s p.740 (Ivey & Morrisey 2000): 0.1 mg/kg in 1 mL water PO q8h for 3 days, then once daily for 2 days.

Small mammals

• Diarrhoea: Plumb’s p.740 (Adamcak & Otten 2000): mice, rats, gerbils, hamsters, guinea pigs, chinchillas 0.1 mg/kg in 1 mL water PO q8h for 3 days, then once daily for 2 days.

Contraindications

MDR1-mutant herding breeds (Collies, Aussies, etc. — opioid CNS toxicity). Infectious/toxin-mediated diarrhoea (slowing motility traps pathogens/toxins — can worsen). Cats (opioid excitation/sensitivity — generally avoid). Suspected GI obstruction. Very young/debilitated animals. Known opioid hypersensitivity.

Species-specific warnings

Dogs: Contraindicated in MDR1 (ABCB1-1Δ) breeds — Collies, Australian Shepherds, etc. — where it causes opioid CNS toxicity at normal doses. Consider MDR1 testing in herding breeds.

Cats: Generally avoid in cats (opioid excitation/sensitivity); use cat-appropriate management of diarrhoea instead.

Adverse effects

• Constipation, bloating, sedation
• CNS/opioid toxicity in MDR1 breeds (sedation, ataxia, respiratory depression) at normal doses
• Excitation in cats
• Worsening of infectious diarrhoea (toxin/pathogen retention)

Drug interactions

• P-glycoprotein inhibitors (ketoconazole, ciclosporin, etc.): increased CNS penetration/toxicity
• Other CNS depressants/opioids: additive central effects (especially if CNS exposure occurs)
• No major other interactions at gut-local doses

Pregnancy and lactation

Limited data; generally avoided unless clearly needed and short-term.

Monitoring

• Diarrhoea response (short-term only — reassess if not resolving / if infectious cause suspected)
• CNS signs (especially in any herding breed — but ideally just avoid in MDR1 breeds)
• Constipation with continued use

Toxicity and overdose

In normal dogs, overdose causes constipation, sedation and (at high doses) opioid CNS/respiratory depression. In MDR1-deficient dogs, even standard doses can cause profound opioid neurotoxicity (sedation, ataxia, drooling, respiratory depression). Cats are prone to opioid excitation. Slowing motility in infectious diarrhoea can worsen the disease.

Management: Antidote: NALOXONE reverses the opioid effects (may need repeating). Supportive care, monitor respiration; decontaminate large recent ingestions. In MDR1 dogs, anticipate prolonged effects and provide supportive care/ventilatory support as needed.

Clinical pearls

• A short-term symptomatic antidiarrhoeal for NON-infectious canine diarrhoea — it slows the gut locally
• NEVER in MDR1/herding breeds (Collies, Aussies) — standard doses cause opioid neurotoxicity; naloxone is the antidote
• Avoid in infectious/toxin diarrhoea (you trap the pathogen/toxin) and in cats
• Use briefly and address the underlying cause; constipation signals you've given enough

Mechanism of action

A peripherally selective mu-opioid agonist that acts on opioid receptors in the intestinal myenteric plexus, slowing propulsive motility, increasing transit time, and reducing intestinal secretion — the antidiarrhoeal effect. Normally it does not reach the CNS because P-glycoprotein (the ABCB1 gene product) pumps it back out of the blood–brain barrier; MDR1-deficient dogs lack this protection, so the drug accumulates centrally and causes opioid neurotoxicity.

Formulations and products

• 2 mg capsule/tablet
• Oral solution 0.2 mg/mL (1 mg/5 mL)
• Imodium — 2 mg capsule, Capsule (human-label)
• Eldoper / Roko — 2 mg tablet/capsule, Tablet / capsule (human-label)

Storage

Capsules/solution: 15–30 °C, dry, protect from light.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other gastrointestinal drugs

• Cisapride
• Famotidine
• Hyoscine Butylbromide (N-Butylscopolammonium)
• Lactulose
• Metoclopramide
• Metronidazole
• Mineral Oil (Liquid Paraffin)
• Mirtazapine

Frequently asked questions