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Antidiarrheal opioid agonist · For Dogs

Imodium dosage reference for dogs (Loperamide)

This page's standard weight-based reference is 0.15 mg per kg (0.07 mg per lb), with Every 8-12 hours recorded as the reference frequency. Use the calculator to see the arithmetic for your dog's weight, then confirm the indication, product, and actual dose with a veterinarian.

Onset
1-2 hours
Duration
8-12 hours
Class
Antidiarrheal opioid agonist

Weight-based calculator estimate from the references listed on this page. This page has not been independently DVM-reviewed — see our methodology .

This information is for educational purposes only. Always consult your veterinarian before giving medication to your pet. Do not use this calculator for emergencies, overdoses, pregnancy, very young animals, very old animals, pets with liver/kidney disease, or pets taking multiple medications.

Each medication page lists the references recorded for its data. The calculator math and editorial presentation are maintained by PetDosageChart; a page is independently DVM-reviewed only when a named reviewer byline appears. See our methodology and limitations.

Loperamide (often known by brand names such as Imodium and Imodium A-D) is an antidiarrheal opioid agonist commonly used in veterinary medicine for Acute diarrhea, Chronic diarrhea, and Inflammatory bowel disease-related diarrhea. Understanding the correct dosage, administration, and potential side effects of Loperamide is critical for your dog’s safety and well-being.

A typical Loperamide dose for dogs is around 0.15 mg/kg Every 8-12 hours, within a usual range of 0.1-0.2 mg/kg. Available forms include Tablet, Capsule, and Liquid.

Calculator Warning: Use this only as an educational estimate. Your veterinarian may prescribe a different dose based on your pet’s condition, age, weight, other medications, and medical history.

Loperamide Dosage Calculator for Dogs

Enter your dog’s weight below to estimate the Loperamide dose from the 0.15 mg/kg guideline. Your veterinarian may adjust it for your dog’s age, condition, and other medications, so treat the result as an educational starting point, not a prescription.

Dosage Calculator · 01

Enter your dog's weight

Quick Dosage Chart

Typical Loperamide amounts for common dog weights, for quick reference:

Dosage Chart · 02

Imodium weight-based reference chart for dogs

Scroll sideways to see full table

Weight Lower Reference Standard Reference Upper Reference Frequency
5 lbs (2.3 kg) 0.23 mg 0.34 mg 0.46 mg Every 8-12 hours
10 lbs (4.5 kg) 0.45 mg 0.67 mg 0.90 mg Every 8-12 hours
15 lbs (6.8 kg) 0.68 mg 1.0 mg 1.4 mg Every 8-12 hours
20 lbs (9.1 kg) 0.91 mg 1.4 mg 1.8 mg (2mg tablet) Every 8-12 hours
25 lbs (11.3 kg) 1.1 mg 1.7 mg (2mg tablet) 2.3 mg (2mg tablet) Every 8-12 hours
30 lbs (13.6 kg) 1.4 mg 2.0 mg (2mg tablet) 2.7 mg Every 8-12 hours
40 lbs (18.1 kg) 1.8 mg (2mg tablet) 2.7 mg 3.6 mg (2 × 2mg) Every 8-12 hours
50 lbs (22.7 kg) 2.3 mg (2mg tablet) 3.4 mg 4.5 mg Every 8-12 hours
60 lbs (27.2 kg) 2.7 mg 4.1 mg (2 × 2mg) 5.4 mg Every 8-12 hours
70 lbs (31.7 kg) 3.2 mg 4.8 mg 6.3 mg (3 × 2mg) Every 8-12 hours
80 lbs (36.3 kg) 3.6 mg (2 × 2mg) 5.4 mg 7.3 mg Every 8-12 hours
90 lbs (40.8 kg) 4.1 mg (2 × 2mg) 6.1 mg (3 × 2mg) 8.2 mg (4 × 2mg) Every 8-12 hours
100 lbs (45.4 kg) 4.5 mg 6.8 mg 9.1 mg Every 8-12 hours
120 lbs (54.4 kg) 5.4 mg 8.2 mg (4 × 2mg) 10.9 mg Every 8-12 hours
150 lbs (68 kg) 6.8 mg 10.2 mg (5 × 2mg) 13.6 mg (7 × 2mg) Every 8-12 hours

Parenthetical tablet amounts are arithmetic comparisons only. They do not account for scoring, release type, concentration, product labeling, or whether this medication is appropriate for an individual animal.

By Weight

Imodium reference by dog weight

Choose a common weight to open its optional reference page. Use the main medication calculator for a different exact weight.

Common-weight pages are convenience views of the same educational reference, not separate medical recommendations.

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How to Give Loperamide to Your Dog

Give loperamide by mouth. Tablets can be given with or without food. If using liquid formulation, measure carefully with a syringe. CRITICAL: Do NOT give to Collies, Australian Shepherds, Shetland Sheepdogs, or any herding breed mix without MDR1 genetic testing — loperamide can cause fatal neurotoxicity in MDR1-mutant dogs. Use only plain loperamide products (no multi-symptom formulas). Limit use to 2-3 days unless directed otherwise by your vet.

It may interact with Other opioids, CNS depressants, Antihistamines, MAO inhibitors, and P-glycoprotein inhibitors (ketoconazole, spinosad).

Side Effects and Safety

Common side effects include Constipation, Bloating, Sedation, and Gas. More serious side effects can occur, such as CNS depression in MDR1-mutant breeds, Severe constipation, Pancreatitis, Toxic megacolon, and Respiratory depression.

Cautions · 12

When Imodium should be used with caution or avoided

Some dogs should not take Imodium, or need a different dose and closer monitoring. Tell your veterinarian about your pet's full health history and every other medication or supplement they take before giving Imodium.

  • MDR1 gene mutation (Collies, Australian Shepherds, Shelties, and related breeds)
  • Infectious diarrhea (bacterial or parasitic)
  • Intestinal obstruction
  • Liver disease

Interactions · 13

Imodium drug interactions

Imodium can interact with other drugs. This list is not complete — always give your veterinarian a full list of your dog's medications and supplements.

Other opioids
CNS depressants
Antihistamines
MAO inhibitors
P-glycoprotein inhibitors (ketoconazole, spinosad)

Calculator Limits · 14

When not to use this calculator

This calculator gives a general educational estimate for a healthy adult dog at a known weight. Do not rely on it in these situations — talk to your veterinarian instead:

  • In an emergency, or after accidental ingestion or a suspected overdose
  • For pregnant or nursing pets
  • For very young or very old dogs
  • For pets with liver disease, kidney disease, or another chronic illness
  • For pets taking several medications at once
  • When you are not sure of your dog's current, accurate weight
  • For combination products that contain additional active ingredients

Overdose · 15

Suspected overdose: what to do

If you think your dog had too much Imodium, or swallowed any medication by accident, act right away. Do not wait for symptoms to appear.

  • Call your veterinarian or the nearest emergency animal hospital.
  • ASPCA Animal Poison Control Center: (888) 426-4435
  • Pet Poison Helpline: (855) 764-7661

A consultation fee may apply to the poison hotlines. Have the medication packaging ready, and note how much your pet may have taken and when. Do not try to make your pet vomit unless a veterinarian tells you to.

When to Call the Vet

If your dog experiences any of the following, contact your veterinarian or an emergency clinic immediately:

Frequently Asked Questions

Frequently Asked · 07

Questions about this medication

Why is loperamide dangerous for Collies and related breeds?
Dogs with the MDR1 (ABCB1) gene mutation lack functional P-glycoprotein at the blood-brain barrier. Loperamide, which normally stays out of the brain, can cross into the CNS in these dogs, causing severe neurological toxicity including sedation, disorientation, tremors, and potentially death. Affected breeds include Collies, Australian Shepherds, Shetland Sheepdogs, and mixes of these breeds.
Can I give my dog Imodium from the pharmacy?
Plain loperamide (Imodium A-D) tablets or liquid may be used, but NEVER use Imodium Multi-Symptom Relief as it contains simethicone or other ingredients. Always confirm the product contains only loperamide. Consult your vet before giving any over-the-counter medication.
How long should I give loperamide to my dog?
Loperamide should typically be used for only 2-3 days for acute diarrhea. If diarrhea persists beyond this, veterinary evaluation is needed to determine the underlying cause. Prolonged use without diagnosis can mask serious conditions.
Should I test my dog for the MDR1 mutation before giving loperamide?
Yes, if your dog is a herding breed or mixed breed of unknown heritage, MDR1 genetic testing is strongly recommended before administering loperamide. Testing is available through veterinary genetics labs and can be done with a simple cheek swab.
When should I NOT give loperamide for diarrhea?
Do not give loperamide if your dog has bloody diarrhea, fever, vomiting, suspected infection, or has ingested toxins. In these cases, diarrhea may be the body's way of expelling harmful agents, and stopping it can worsen the condition. Always see a vet for diarrhea lasting more than 24-48 hours.

Use This Guide Safely · 08

What weight alone cannot tell you

The calculator performs one narrow job: it multiplies your dog's weight by the lower, standard, and upper mg/kg values recorded for Imodium. It cannot decide whether this drug, indication, formulation, or schedule is appropriate for an individual animal.

Context in this medication record

Commonly listed uses
Acute diarrhea, Chronic diarrhea, Inflammatory bowel disease-related diarrhea
Recorded forms
Tablet, Capsule, Liquid
Reference timing
Every 8-12 hours; onset 1-2 hours; duration 8-12 hours

Individual checks a calculator cannot perform

  • Confirm the diagnosis and the reason this medication is being considered.
  • Match the exact product, concentration, route, and whether a tablet may be split.
  • Account for age, pregnancy, organ function, genetics, allergies, and prior reactions.
  • Review every prescription, over-the-counter product, and supplement your pet takes.

Recorded cautions

MDR1 gene mutation (Collies, Australian Shepherds, Shelties, and related breeds); Infectious diarrhea (bacterial or parasitic); Intestinal obstruction; Liver disease.

Recorded interactions

Other opioids; CNS depressants; Antihistamines; MAO inhibitors; P-glycoprotein inhibitors (ketoconazole, spinosad).

These lists reproduce the structured record used by this page and may not be exhaustive. Show your veterinarian the product label and your dog's complete medication list before acting on a number.

Related · 08

Related medications for dogs

Sources · 09

Sources & references

The structured medication record behind this page names the references below. The links open the publisher or official resource; they do not turn this page into a prescription for an individual animal.

Source names are shown at the record level; passage-level page and label citations are still being added. Read our methodology and limitations.

Transparency · 11

How this page was made

This page's structured medication record includes Plumb's Veterinary Drug Handbook among its source names. PetDosageChart applies the record's mg/kg values to the entered weight and presents the arithmetic result. A source record is not the same as an individualized prescription or an independent clinical review.

Sources cited
  • Plumb's Veterinary Drug Handbook
  • Merck Veterinary Manual
Calculator formula
Doses scale linearly from a standard basis of 0.15 mg per kg (0.07 mg per lb) of body weight, given Every 8-12 hours. The calculator multiplies that basis by your dog's weight and shows an arithmetic comparison with recorded tablet sizes. That comparison does not determine whether a tablet is scored, splittable, or appropriate for your pet.
Editorial owner
Prepared and maintained by the PetDosageChart editorial team, a software-led publisher and not a veterinary practice.
DVM review status
Not independently DVM-reviewed. A named reviewer and review date appear here only after a confirmed review.

More on our methodology and editorial process — how we source, calculate, and review dogs dosage data.

Safety · 10

More resources