Atropine Sulfate

What is this medication for?

• Preanesthetic (↓secretions), unusually slow heart rate/AV block, organophosphate/carbamate/muscarinic mushroom antidote, bronchoconstrictive disease, hypersialism

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

• Atropine response test (differentiating vagal vs. non-vagal bradyarrhythmias): give 0.04 mg/kg into a vein, wait 15 min, recheck ECG — persistent sinus unusually fast heart rate >140 bpm expected if vagally mediated.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• Dry mouth, dysphagia, constipation, vomiting, thirst (Dose-related, common at high doses)
• Urinary retention/hesitancy (Dose-related)
• Tachycardia (or initial unusually slow heart rate at low doses), high blood pressure/low blood pressure, arrhythmias (Dose-related)
• Mydriasis, cycloplegia, blurred vision (Dose-related)

Worth a phone call to your veterinarian

• Any new symptom that worries you.

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Trouble breathing, collapse, seizures, severe vomiting or diarrhea, facial swelling, or pale gums

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Narrow-angle glaucoma, unusually fast heart rate (thyrotoxicosis/cardiac), stomach/intestinal obstructive disease/ileus, severe ulcerative colitis, obstructive uropathy, myasthenia gravis (unless reversing muscarinic drug effects)
• has or has had: Not effective for unusually slow heart rate in puppies <14 days or kittens <11 days old; caution combining with alpha-2 agonists (dexmedetomidine) — controversial, may worsen high blood pressure/arrhythmias; rabbits often have endogenous atropinesterase — use glycopyrrolate instead

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Alpha-2 agonists (dexmedetomidine, medetomidine)
  • Amitraz
  • Antihistamines, phenothiazines, TCAs, other anticholinergics
  • Metoclopramide
  • Digoxin (slow-dissolving tablets)

Storage and handling

Tightly sealed container, room temperature.

Good to know

• Atropine response test (differentiating vagal vs. non-vagal bradyarrhythmias): give 0.04 mg/kg into a vein, wait 15 min, recheck ECG — persistent sinus unusually fast heart rate >140 bpm expected if vagally mediated.
• In organophosphate/carbamate toxicity, dose to effect (drying of secretions) rather than a fixed dose — repeat as needed since this reflects a large functional antidote reserve.
• Do NOT rely on atropine to reverse unusually slow heart rate in very young neonates — it is reportedly ineffective in puppies <14 days/kittens <11 days.