Atropine Sulfate: veterinary dose and monograph

At a glance

Drug class

Veterinary drug

Also known as

Atroject, Atropine SA, Atropine LA, AtroPen

Species with doses

Dogs, Cats, Cattle, Horses, Goats, Sheep, Pigs, Birds, Rabbits, Ferrets, Guinea pigs, Reptiles, Chinchillas, Rats, Hedgehogs, Sugar gliders and Primates

General dose range

0.02–0.04 mg/kg IV as needed — check the species tables for the indication

Routes

SC, IV, IM, IP

Last reviewed

1 October 2026

Indications

• Pre-anaesthetic — reduce respiratory secretions
• Sinus bradycardia, sinoatrial arrest, incomplete AV block
• CPR / CPCR adjunct
• Antidote: organophosphate / carbamate / muscarinic mushroom toxicity
• Hypersialism
• Bronchodilation (rescue dose, equine RAO)

Atropine Sulfate 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

• Pre-anaesthetic: Papich 5e: 0.02–0.04 mg/kg IV, IM or SC (range 0.01–0.06 mg/kg by indication). Plumb’s p.128: 0.02–0.04 mg/kg SC, IM or IV (Morgan); geriatric patients 0.01–0.02 mg/kg; label 0.074 mg/kg. Not for routine use — only when bradycardia or secretions are a concern.
• CPCR / bradycardia: Papich 5e: cardiac arrest 0.04 mg/kg IV; sinus bradycardia 0.005–0.01 mg/kg. Plumb’s p.128 (Plunkett & McMichael): CPCR 0.04 mg/kg IV or IO every 3–5 min to a maximum of 3 doses; intratracheal 0.08–0.1 mg/kg diluted in 5–10 mL sterile water. Atropine response test: 0.04 mg/kg IV (ECG at 15 min) or SC (ECG at 30 min).
• Cholinergic / OP toxicity: Papich 5e: organophosphate/carbamate toxicosis 0.2–0.5 mg/kg as needed IV, IM or SC. Plumb’s p.128 (Firth 2000): 0.2–0.5 mg/kg, ¼ IV and the remainder IM or SC; repeat to effect (dry mucous membranes, reduced secretions — not heart rate alone). Use the 15 mg/mL product for large doses.

Cats

• Pre-anaesthetic: Papich 5e: 0.02–0.04 mg/kg q6–8h IV, IM or SC. Plumb’s p.128: 0.02–0.04 mg/kg SC, IM or IV (Morgan); geriatric 0.01–0.02 mg/kg; CPCR 0.04 mg/kg IV/IO up to 3 doses.
• OP / carbamate toxicity: Plumb’s p.128 (Morgan 1988): 0.2–2 mg/kg — ¼ IV, the remainder SC or IM. Papich 5e: 0.2–0.5 mg/kg as needed IV, IM or SC. Titrate to control of muscarinic signs.

Cattle

• OP toxicity: Plumb’s p.129 (Bailey 1986): 0.5 mg/kg average dose — ¼ IV, the remainder SC or IM; may repeat q3–4h for 1–2 days. Papich 5e (ruminants): 0.1 mg/kg IV then 0.4 mg/kg IM, repeat as needed. FARAD’s 28-day meat / 6-day milk withdrawal applies to doses up to 0.2 mg/kg — at these antidotal doses obtain FARAD advice for a longer withdrawal.

Horses

• Bradyarrhythmia (vagal): Plumb’s p.129: 0.01–0.02 mg/kg IV (Mogg 1999); 0.045 mg/kg parenterally (Hilwig). Atropine strongly inhibits GI motility in horses — watch for ileus/colic. ARCI Class 3.
• Bronchodilator rescue (RAO): Papich 5e: equine asthma/RAO 0.022 mg/kg IV once. Plumb’s p.129: 5 mg IV for a 400–500 kg horse (Beech); 5–7 mg per 450 kg IV as a single rescue dose only (Rush) — duration 0.5–2 h; ileus, CNS toxicity, tachycardia and thickened mucus limit use to one dose.
• OP poisoning: ¼ IV + ¾ SC. Endpoint: mydriasis + absence of salivation. REFERENCE CONFLICT — not resolved: Plumb’s p.129 gives about 1 mg/kg IV to effect (Oehme 1987) or 0.22 mg/kg (¼ IV, rest SC/IM; label), whereas Papich 5e gives 0.02–0.04 mg/kg IM/SC repeated as needed. Titrate from the low end against muscarinic signs; atropine profoundly inhibits equine GI motility (colic/ileus risk).

Goats

• OP / carbamate toxicity: Plumb’s p.129: sheep & goats — use the cattle dose, 0.5 mg/kg (¼ IV, remainder SC/IM), may repeat q3–4h for 1–2 days. Papich 5e (ruminants): 0.1 mg/kg IV followed by 0.4 mg/kg IM, repeat as needed. Titrate to mydriasis and dry mucosa. FARAD (doses up to 0.2 mg/kg): 28 d meat / 6 d milk.

Sheep

• OP / carbamate toxicity: Plumb’s p.129: sheep & goats — use the cattle dose, 0.5 mg/kg (¼ IV, remainder SC/IM), may repeat q3–4h for 1–2 days. Papich 5e (ruminants): 0.1 mg/kg IV followed by 0.4 mg/kg IM, repeat as needed. Titrate to mydriasis and dry mucosa.

Pigs

• Pre-anaesthetic: Papich 5e: anaesthesia adjunct 0.02 mg/kg IV or 0.04 mg/kg IM. Plumb’s p.129 (Thurmon & Benson): 0.04 mg/kg IM. FARAD: 28-day meat withdrawal for food animals at doses up to 0.2 mg/kg.
• Organophosphate / cholinesterase-inhibitor poisoning: Papich 5e (Large Animal Dosage, Pigs): 0.1 mg/kg IV FOLLOWED BY 0.4 mg/kg IM; repeat as needed. This antidotal dose is 10x the 0.04 mg/kg anaesthetic-adjunct dose - titrate against muscarinic signs (salivation, bronchorrhoea, bradycardia), not to a fixed number.

Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

• OP toxicity: Plumb’s p.129 (Bailey 1986): 0.5 mg/kg average dose — ¼ IV, the remainder SC or IM; may repeat q3–4h for 1–2 days. Papich 5e (ruminants): 0.1 mg/kg IV then 0.4 mg/kg IM, repeat as needed. FARAD’s 28-day meat / 6-day milk withdrawal applies to doses up to 0.2 mg/kg — at these antidotal doses obtain FARAD advice for a longer withdrawal.

Birds

• OP toxicity: Plumb’s p.129: 0.2 mg/kg IM every 3–4 h as needed, giving ¼ of the dose initially; combine with pralidoxime 10–20 mg/kg IM q8–12h (not in raptors, and never for carbamates). Diagnostic test: 0.02 mg/kg IV in a bradycardic bird — failure to reverse suggests OP toxicity (LaBonde).
• Pre-anaesthetic: Plumb’s p.129 (Clubb 1986): 0.04–0.1 mg/kg IM or SC once. Diagnostic aid for OP poisoning in a bradycardic bird: 0.02 mg/kg IV — if bradycardia does not reverse, suspect OP toxicity (LaBonde 2006).

Rabbits

• Premedication / vagally-mediated bradycardia: Plumb’s 10e p.115 (extra-label): rabbits 0.05–0.25 mg/kg IM or SC for premedication and vagally-mediated bradycardia. Atropine is INEFFECTIVE in ≈50% of rabbits because of serum atropinase, so glycopyrrolate is preferred.
• Organophosphate toxicity: Plumb’s p.129 (Ivey & Morrisey 2000) and Carpenter’s Table 10-4: rabbits 10 mg/kg SC every 20 minutes for organophosphate toxicity — very high doses are needed because of serum atropinase.

Ferrets

• Pre-anaesthetic / bradycardia: Plumb’s p.129 (Williams 2000): ferrets 0.05 mg/kg SC or IM as a premedicant. (The previous 0.06–0.12 mg/kg figure was Plumb’s CATTLE pre-anaesthetic dose.)

Guinea pigs

• Anaesthetic premedication: Plumb's p.1177 (Bennett 2009): rodents — atropine 0.05 mg/kg IP as part of xylazine/ketamine anaesthesia. Note many rodents have some atropinesterase; glycopyrrolate is an alternative.

Reptiles

• Organophosphate toxicity: Plumb’s p.129 (Gauvin 1993): most reptiles 0.1–0.2 mg/kg SC or IM as needed for OP toxicity. Ptyalism in tortoises: 0.05 mg/kg SC or IM once daily. (The earlier 0.01–0.04 mg/kg ‘pre-anaesthetic’ figure is not in Plumb’s.)

Chinchillas

• Anaesthetic premedication: Plumb's p.1177 (Bennett 2009): rodents — atropine 0.05 mg/kg IP with xylazine/ketamine.

Rats

• Anaesthetic premedication: Plumb's p.1177 (Bennett 2009): rodents — atropine 0.05 mg/kg IP with xylazine/ketamine.

Hedgehogs

• Pre-anaesthetic / bradycardia: Carpenter Exotic Animal Formulary 6th ed, Table 8-4 & 8-7 (p.516, 519): hedgehogs 0.01–0.05 mg/kg SC/IM (preanaesthetic anti-sialogogue; 0.05–0.2 mg/kg for bradycardia). Increased salivary viscosity may offset the benefit — weigh use.

Sugar gliders

• Pre-anaesthetic / bradycardia: Carpenter Exotic Animal Formulary 6th ed, Table 7-3 (p.499): sugar gliders 0.01–0.02 mg/kg SC/IM, or 0.02–0.04 mg/kg SC/IM/IV.

Primates

• Pre-anaesthetic / bradycardia (monkeys): Carpenter Exotic Animal Formulary 6th ed, Table 13-7 (p.704): chimpanzees/monkeys/marmosets 0.02–0.04 mg/kg SC/IM/IV; macaques/baboons/marmosets 0.02–0.05 mg/kg (use higher dose in marmosets).

Contraindications

Narrow-angle glaucoma, tachyarrhythmias, thyrotoxicosis, GI obstruction / paralytic ileus, severe ulcerative colitis, obstructive uropathy, myasthenia gravis. Caution in horses (may induce colic) and cattle (rumen stasis lasting days). Not effective in puppies <14 d or kittens <11 d. Use glycopyrrolate (not atropine) in rabbits — many have endogenous atropinesterase.

Species-specific warnings

Horses: AVOID systemic atropine — causes prolonged ileus, colic, even death (esp. foals). Topical ophthalmic for uveitis is acceptable.

Dogs: Standard pre-anaesthetic / emergency drug. Pre-treat alpha-2 / opioid bradycardia at 0.04 mg/kg IM. CPR dose 0.04 mg/kg IV.

Cats: Same indications as dogs but cats are MORE sensitive — use lower end of range (0.02 mg/kg IV pre-anaesthetic).

Cattle: AVOID for bloat — worsens ileus. OP poisoning: same indication as small animals; titrate to drying of secretions.

Birds: Used for OP toxicosis at 0.1–0.2 mg/kg IM. Lower doses (0.02 mg/kg) for pre-anaesthetic in raptors.

Adverse effects

• Xerostomia, dysphagia, constipation, vomiting, thirst
• Urinary retention
• Sinus tachycardia (high dose), bradycardia (very low dose)
• CNS: ataxia, seizures, respiratory depression at toxic doses
• Mydriasis, photophobia, blurred vision
• Cattle: prolonged inappetence and rumen stasis

Drug interactions

• Alpha-2 agonists (xylazine, detomidine, dexmedetomidine): atropine PRE-TREATMENT recommended to blunt vagal bradycardia
• Phenothiazines (acepromazine): additive anticholinergic effects
• Tricyclic antidepressants (amitriptyline): additive anticholinergic toxicity (mydriasis, ileus, tachycardia)
• Cisapride / metoclopramide: atropine antagonises prokinetic effect
• Beta-blockers (propranolol, atenolol): atropine may partly counter beta-blocker bradycardia
• Glycopyrrolate: similar pharmacology — do NOT combine routinely (additive)
• Other organophosphates (e.g. accidental cypermethrin / pyrethrin combos): atropine is the antidote — pralidoxime (2-PAM) is the cholinesterase reactivator

Pregnancy and lactation

Generally safe at single peri-operative doses. Crosses placenta — fetal tachycardia possible. Excreted in milk; can suppress milk let-down. Use cautiously in late pregnancy at sustained doses. FDA Category C.

Monitoring

• Heart rate, ECG (arrhythmias on continuous monitor in critical patients)
• GI motility — auscultate gut sounds, especially horses and foals
• Urinary output — risk of retention
• Pupillary response — mydriasis confirms effect, persists 24–48 h
• Body temperature — hyperthermia risk in overdose or hot environments
• For OP poisoning: monitor pupil size and bronchial secretions as titration end-points (NOT heart rate alone)

Toxicity and overdose

Therapeutic-dose effects: tachycardia, mydriasis, dry mouth, ileus, urinary retention. Overdose: severe tachyarrhythmias, CNS excitement (restlessness, seizures), hyperthermia ("blind as a bat, dry as a bone, red as a beet, hot as a hare, mad as a hatter"). Horses and cats are more sensitive than dogs — ileus can be prolonged and dangerous. Foals: prolonged ileus, colic, death.

Management: No specific antidote. Discontinue. Supportive: IV fluids, diazepam 0.5 mg/kg IV for excitement / seizures, beta-blocker (esmolol, propranolol) for severe tachyarrhythmia, active cooling for hyperthermia. Physostigmine (cholinesterase inhibitor) reverses CNS effects — 0.02 mg/kg slow IV — but rarely needed and can cause cholinergic crisis. Activated charcoal if recent oral overdose.

Clinical pearls

• Pre-anaesthetic for opioid + alpha-2 protocols: 0.04 mg/kg IM 10–15 min before — blunts bradycardia
• CPR / asystole: 0.04 mg/kg IV/IO/IT — first-line for bradyarrhythmia-driven cardiac arrest
• Organophosphate / carbamate toxicosis: 0.2–0.5 mg/kg IV (small animals) — titrate to drying of secretions (NOT heart rate). PRALIDOXIME (2-PAM) is the cholinesterase reactivator — give within 24–36 h of exposure.
• Horses: AVOID systemic use — prolonged ileus / colic. Topical ophthalmic atropine OK for uveitis.
• Foals: AVOID — fatal ileus reported even at low doses.
• Cattle bloat: NOT first-line — orogastric tube / trocar are preferred; atropine can worsen ileus.
• For ophthalmic uveitis: 1% atropine drops q6h until pupil dilated, then q24h — cycloplegia relieves ciliary spasm pain
• Bradycardia with hypotension under anaesthesia: 0.02 mg/kg IV (lower than CPR dose) — increases HR without overshoot tachycardia

Mechanism of action

Competitive muscarinic acetylcholine receptor antagonist (tertiary amine). Blocks parasympathetic stimulation of cardiac (vagal), salivary, lacrimal, gastric, bronchial, and pupillary smooth muscle. Cardiac: increased SA node firing (positive chronotropy), increased AV conduction. GI / urinary: reduced motility, urinary retention. Bronchial: bronchodilation, decreased secretions. Pupil: mydriasis, cycloplegia. Crosses blood-brain barrier (CNS effects). The classic anti-AChE / organophosphate poisoning antidote.

Formulations and products

• Atropine SA 0.54 mg/mL (small animal)
• Atropine LA 15 mg/mL (organophosphate antidote)

Storage

Injectable: 15–25 °C, protect from light. Multidose vial: discard 28 days after broaching. Ophthalmic solution: 15–25 °C. Auto-injectors (AtroPen): 15–25 °C, protect from light and freezing.

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.

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Frequently asked questions