Skip to main content


Generic name: physostigmine [ FYE-so-STIG-meen ]
Brand name: Antilirium
Dosage form: injectable solution (1 mg/mL)
Drug class: Antidotes

Medically reviewed by on Mar 31, 2022. Written by Cerner Multum.

What is physostigmine?

Physostigmine affects chemicals in the body that control the signals sent from the nervous system to the muscles to activate muscle movement.

Physostigmine is used to reverse the effects of certain drugs or substances that interfere with this nerve-muscle communication. Such substances include atropine, scopolamine, belladonna, antihistamines, some antidepressants, and other anticholinergic (AN tye KOE lin ER jik) drugs.

Physostigmine may also be used for purposes not listed in this medication guide.


In an emergency situation it may not be possible to tell your caregivers about your health conditions. Make sure any doctor caring for you afterward knows you have received physostigmine.

Before taking this medicine

You should not be treated with physostigmine if you are allergic to it, or if you have:

  • asthma;

  • diabetes;

  • bladder obstruction or other urination problems;

  • a blockage in your digestive tract (stomach or intestines);

  • heart disease; or

  • gangrene (damaged skin and muscle tissue caused by infection or lack of blood supply).

If possible before you receive physostigmine, tell your doctor if:

In an emergency situation it may not be possible to tell your caregivers if you are pregnant or breast-feeding. Make sure any doctor caring for your pregnancy or your baby knows you have received this medicine.

How is physostigmine given?

Physostigmine is injected into a muscle or into a vein through an IV. A healthcare provider will give you this injection.

When injected into a vein, physostigmine must be given slowly.

Your breathing, blood pressure, oxygen levels, and other vital signs will be watched closely while you are receiving physostigmine.

You may need repeat doses of physostigmine, depending on how your body responds to it. Your doctor will determine how long to treat you with physostigmine.

What happens if I miss a dose?

Because you will receive physostigmine in a clinical setting, you are not likely to miss a dose.

What happens if I overdose?

Since physostigmine is given by a healthcare professional in a medical setting, an overdose is unlikely to occur.

What should I avoid after receiving physostigmine?

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

Physostigmine side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Tell your caregivers right away if you have:

  • increased urination or bowel movements;

  • stomach cramps;

  • severe or worsening nausea or vomiting;

  • increased sweating;

  • blurred vision; or

  • excessive saliva in your mouth.

Common side effects of physostigmine may include:

  • nausea, vomiting;

  • increased salivation; or

  • slow heartbeats.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Physostigmine dosing information

Usual Adult Dose for Anticholinergic Syndrome:

Post anesthesia care:

Initial dose: 0.5 to 1 mg, IM or slow IV, at no more than 1 mg/minute
-May repeat dose at 10 to 30 minute intervals if desired response is not obtained

Overdose of drugs that cause anticholinergic syndrome:

2 mg, IM or slow IV, at no more than 1 mg/minute
-May repeat dose if life threatening signs (e.g. arrhythmia, convulsions, coma) occur

Usual Pediatric Dose for Anticholinergic Syndrome:

0.02 mg/kg, IM or slow IV, at no more than 0.5 mg/minute
-May repeat dose at 5 to 10 minute intervals if toxic effects persist (and no cholinergic effects) until a therapeutic effect is obtained.
Maximum dose: 2 mg

What other drugs will affect physostigmine?

Other drugs may interact with physostigmine, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.

Further information

  • Your doctor can provide more information about physostigmine.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.