Anticholinergics is a topic covered in the Washington Manual of Medical Therapeutics.

To view the entire topic, please or purchase a subscription.

The Washington Manual of Medical Therapeutics helps you diagnose and treat hundreds of medical conditions. Consult clinical recommendations from a resource that has been trusted on the wards for 50+ years. Explore these free sample topics:

Washington Manual

-- The first section of this topic is shown below --

General Principles

Anticholinergic effects are primarily due to blockade of muscarinic receptors (i.e., antimuscarinic effects) and, therefore, mainly affect parasympathetic functions.


Anticholinergic poisoning occurs either from intentional ingestion of certain plants or over-the-counter medications (e.g., Jimson weed, diphenhydramine)1 or from accidental overdosing (e.g., medical noncompliance, polypharmaceutical regimens).2


Drugs and medications with anticholinergic effects include the following:

  • Anticholinergics: Atropine, scopolamine, benztropine, glycopyrrolate, ipratropium
  • Antihistamines: Diphenhydramine, promethazine, doxylamine
  • Antipsychotics: Chlorpromazine, clozapine, olanzapine, quetiapine
  • Antidepressants: Amitriptyline, nortriptyline, imipramine, desipramine
  • Antiparkinson drugs: Benztropine, trihexyphenidyl
  • Mydriatics: Cyclopentolate, homatropine, tropicamide
  • Muscle relaxants: Cyclobenzaprine
  • Plants: Belladonna, Jimson weed, Amanita mushrooms


  • Blockade of muscarinic receptors (i.e., parasympathetic autonomic nervous system [ANS], except for the sympathetically innervated sweat glands) leads to the so-called anticholinergic toxidrome.
  • Tachycardia is one of the main symptoms in anticholinergic poisoning. Vagal blockade of cardiac muscarinic receptors leads to unopposed sympathetic stimulation of the myocardium.
  • Some anticholinergic drugs can also cross the blood–brain barrier and interact with muscarinic receptors in the cortex and subcortical regions of the brain causing anticholinergic CNS manifestations.

Associated Conditions

  • Antihistamines and cyclic antidepressants also block sodium channels and cause additional cardiac symptoms such as dysrhythmias and QRS prolongations.
  • Potassium channel blockade may result in QTc prolongation and TdP.

-- To view the remaining sections of this topic, please or purchase a subscription --