Diphenoxylate + Atropine

By Krista Williams, BSc, DVM, CCRP

What is diphenoxylate + atropine?

Diphenoxylate + atropine (brand name: Lomotil®) is an opioid combination medication used to treat diarrhea or coughing in dogs and diarrhea in cats. Its use in cats is not generally recommended.

Its use in dogs and cats is “off label” or “extra label”. Many drugs are commonly prescribed for off-label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.

How is diphenoxylate + atropine given?

  • Give diphenoxylate + atropine by mouth in the form of a tablet or liquid. 
  • It may be given with or without food; however, if vomiting occurs when dosed on an empty stomach, give future doses with food.
  • Measure liquid forms carefully.

This medication takes effect quickly, in about 1 to 2 hours, and your pet’s clinical signs should improve after that.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember; however, if it is close to time for the next dose, skip the dose you missed, give it at the next scheduled time, and return to the regular dosing schedule.

Are there any potential side effects?

The most common side effects include constipation, bloating, and sleepiness.

Rare, SERIOUS ADVERSE REACTIONS associated with this drug may occur without warning including:

  • pancreatitis
  • vomiting
  • worsening diarrhea
  • appetite loss
  • extreme lethargy
  • jaundice: yellowing of skin, eyes, gums
  • hyperexcitability in cats
  • overdose may cause fever, high heart rate (tachycardia)

This short-acting medication should stop working within 24 hours.

Are there any risk factors for this medication?

Diphenoxylate + atropine SHOULD NOT BE USED in pets:

  • that are allergic to either of the medications in the combination product
  • with diarrhea due to a toxin or an infection (i.e., parvovirus)
  • with liver failure
  • with obstructive jaundice
  • with intestinal obstruction

This combination should be USED WITH CAUTION in:

  • pets that are older or debilitated
  • pets that have Addison’s disease (hypoadrenocorticism), hypothyroidism, liver disease, or severe kidney failure
  • pets with respiratory disease
  • pets with central nervous system depression such as those with head injury or hepatic encephalopathy
  • pets with acute abdominal conditions
  • cats

Are there any drug interactions I should be aware of?

Certain medications should be used with caution when given with diphenoxylate + atropine, including:

  • any medication that causes sedation, including phenobarbital, cannabidiol (CBD), and acepromazine
  • antihistamines
  • amantadine
  • MAO inhibitors like selegiline (Anipryl®), amitraz (Preventic®, Mitaban®)
  • promotility medications (metoclopramide, cisapride)
  • amitriptyline (Elavil®) and clomipramine (Clomicalm®)

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is any monitoring needed with this medication?

  • You and your veterinarian should monitor your pet to be sure that the medication is working.
  • Monitor your pet for any adverse effects and report any concerns to your veterinarian.

How do I store diphenoxylate + atropine?

Store this medication at room temperature between 68°F and 77°F (20°C and 25°C) and protect it from light.

Diphenoxylate + atropine is a controlled substance, which means that it has been designated by the Drug Enforcement Administration (DEA) as having a potential for diversion to people other than the patient prescribed. Use of a controlled substance in any person or animal other than that for which it is prescribed is illegal. Therefore, this medication should be stored in a locked cabinet or safe that cannot be easily moved, with access limited to only those that need to administer the medication. Monitor the amount of medication remaining to ensure the expected amount is present.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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