Diphenoxylate-atropine (Lomotil): what it treats, how to take it, side effects
Last updated September 3, 2026.
Diphenoxylate-atropine, sold as Lomotil, is a prescription medicine that slows the gut to control diarrhea. Each tablet pairs 2.5 mg of diphenoxylate, an opioid-related gut-slowing agent, with a small amount of atropine added to discourage taking more than prescribed.
What does it treat?
It is used alongside fluid and electrolyte replacement to manage diarrhea in patients 13 and older. It reduces the number and urgency of bowel movements; it does not treat the cause. Diarrhea from certain infections, including C. difficile, should not be slowed down at all, which is why the diagnosis matters before the drug.
How do you take it?
The usual adult starting dose is 2 tablets (5 mg diphenoxylate) four times a day, with a maximum of 20 mg of diphenoxylate per day. Once the diarrhea is controlled, the dose is reduced, often to as little as 2 tablets a day. Acute diarrhea usually improves within 48 hours; if it has not, or if it worsens, or if it is not clearly better within 10 days, stop the drug and call your doctor. Keep fluids up while you take it. For a missed dose, take it when remembered unless the next dose is near, and never double up.
Side effects to know
- Common: drowsiness, dizziness, dry mouth, nausea, and abdominal discomfort.
- Serious: slowed or difficult breathing, severe bloating or worsening belly pain, confusion, fast heartbeat, and signs of dehydration. In overdose, breathing can slow dangerously and may be delayed for many hours after the dose.
Who should not take it?
It is not for children under 6, and accidental swallowing by a small child can cause life-threatening breathing problems, so store it locked away. It should not be used for diarrhea from C. difficile or toxin-producing bacteria, or by people with obstructive jaundice or severe liver disease. Diphenoxylate can be habit-forming at high doses; the atropine exists to make overuse unpleasant. MAO inhibitors and other sedating drugs interact with it, and pregnancy requires a doctor's judgment.
When is it an emergency?
Call 911 for slow, shallow, or stopped breathing, unresponsiveness, or extreme sleepiness after taking this medicine, especially in a child. Severe abdominal swelling with vomiting, or signs of severe dehydration such as fainting or no urination, also mean emergency care. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Why is atropine in Lomotil?
The atropine dose is too small to treat anything. It is there on purpose to discourage overuse: taken in excess, atropine causes unpleasant effects like a racing heart, dry mouth, and blurred vision, which deters taking more diphenoxylate than prescribed.
Is Lomotil habit-forming?
It can be. Diphenoxylate is chemically related to opioid pain medicines, and at higher than prescribed doses it can produce dependence, which is why it is a federally controlled substance. At normal doses for short courses, that risk is low, but do not take more, more often, or longer than directed.
How fast does Lomotil work?
The label notes that clinical improvement in acute diarrhea is usually seen within 48 hours. If you have had no improvement by then, or things get worse at any point, stop taking it and call your doctor rather than pushing through.
Can I get Lomotil prescribed online?
Diphenoxylate-atropine is a controlled substance, so a first prescription is not something an online visit can typically start. What telehealth can do is evaluate your diarrhea, recommend fluids and non-controlled treatments, and route you to in-person care when a controlled medicine or an exam is warranted.
Can I drink alcohol while taking Lomotil?
No. Alcohol adds to the drowsiness and dizziness this medicine causes and increases the risk of dangerous sedation. Skip alcohol until you are done with the course and feeling normal.
Is Lomotil safe for kids?
It is contraindicated under age 6 and not recommended for young children generally, because breathing problems from even a small accidental dose can be severe and delayed. It is approved only for patients 13 and older, and it must be stored where children cannot reach it.