Physostigmine
Also known as: Antilirium, Anticholium
This medication is strictly for use in a clinical setting. * **Direct Supervision:** It must be administered in a veterinary hospital where direct veterinary supervision and emergency monitoring are available. * **Not for Home Use:** Due to the risk of severe and potentially life-threatening side effects, this drug is never dispensed for owners to administer at home.
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
Veterinary professional? See the full dosing-by-species reference on VetSheet →
What it is used for
- For reversal of tall larkspur (Delphinium barbeya) poisoning
- Provocative test in diagnosing cataplexy or narcolepsy
- Provocative test in diagnosing cataplexy or narcolepsy
- To temporarily reverse the CNS effects of ivermectin toxicosis in support of the diagnosis
- To temporarily reverse the CNS effects of ivermectin toxicosis in support of the diagnosis
- Provocative test for narcolepsy/cataplexy
How it is given
Possible side effects
- Miosis
- Bronchial constriction
- Hypersalivation
- Muscle weakness
- Sweating (in species with sweat glands)
- Seizures
- Bradycardia
- Tachycardia
- Asystole
- Nausea
- Vomiting
- Diarrhea
- Depolarizing neuromuscular block
- Pulmonary edema
- Respiratory paralysis
Cautions & contraindications
- Prior hypersensitivity reactions to physostigmine or sulfites
- Bronchoconstrictive disease (asthma)
- Gangrene
- Diabetes mellitus
- Cardiovascular disease
- Mechanical obstruction of the GI or urinary tract
- Any vagotonic state
- Concurrent use of choline esters or depolarizing neuromuscular blocking agents
- > **WARNING:** Toxic effects from this drug can be serious and life-threatening. Must be administered with direct patient supervision. * **Cholinergic Crisis Risk:** Increased risk when used in the absence of anticholinergic toxicity or to treat tricyclic/tetracyclic antidepressant overdoses. * **Administration Rate:** Rapid IV administration increases the potential for bradycardia, hypersalivation, or seizures. Must be given slowly. * **Antidote Availability:** Atropine must be readily available when administering physostigmine. * **Neonatal Toxicity:** The injection contains benzyl alcohol, which may be toxic to neonatal animals. * **Pregnancy:** Weigh potential risks versus benefits. Teratogenic effects have been observed in mice.
Drug interactions
- Choline esters (bethanechol, carbachol, methacholine): May cause additive adverse cholinergic effects.
- Organophosphates: May cause additive adverse cholinergic effects.
- Succinylcholine: High doses of physostigmine may cause muscle fasciculations or depolarization block, which may be additive to the effects of succinylcholine-like neuromuscular blockers.
Frequently asked questions
What is Physostigmine used for in pets?
This medication is strictly for use in a clinical setting. • Direct Supervision: It must be administered in a veterinary hospital where direct veterinary supervision and emergency monitoring are available. • Not for Home Use: Due to the risk of severe and potentially life-threatening side effects, this drug is never dispensed for owners to administer at home.
Is Physostigmine safe for my pet?
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
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