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Link to 2.1.11.4.1 Anticholinergics Teaching Resources
Link to Problems for Discussion
Anticholinergic Toxidrome
Introduction
Anticholinergic toxicity, to varying degrees, is seen relatively frequently in toxicology patients. The main clinical challenge is the safe management of the delirium which occurs due to ventra anticholinergic effects.
The mainstay of treatment is supportive care, whilst time is allowed for the toxicity to resolve; however, patients frequently require sedation and antidotal therapy with physostigmine/rivastigmine for both their own and staff safety.
Anticholinergic drugs
Ther are many drugs and natural substances that have anticholinergic effects.
Pure anticholinergic agents include:
- Atropine
- Benzatropine
- Hyoscine
Drugs with anticholinergic effects include:
- Antihistamines
- Tri-cyclic antidepressants
- Antipsychotics e.g. quetiapine, olanzapine
Plants with anticholinergic effects include:
- Brugmansia species
- Atropa belladonnna
- Datura stamonium
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Mechanism of Toxic Effects
Agents causing antichoinergic toxicity, do so by blocking the muscarinic acetylcholine receptors in the autonomic and central nervous system. This is a competative blockade, which becomes important when understanding the role of acetylcholinesterase inshinotrs in its treatment.
It is the blockade at the central muscarinic-1 (M1) receptors that are most important in driving the delirium.
Synape showing role of acetylcholine, the acetylcholine receptor and acetylcholinesterase
Clinical Presentaion
The anticholinergic toxidrome consists of both central and peripheral effects. It is common for the peripheral effects to abate before the central effects, meaning htat later in the course of the toxidrome, patients may present with delirium as the main or sole effect.
Most anticholinergic toxicity seen in clinical practive, results from ingestion of agents with multiple receptor effects (as apposed to pure anticholinergics) this may also lead to clouding of the classic toxidrome - a common example being miosis in a patient suffering from an anticholinergice delirium secondary to olanzapine or quetipaine, due to their alpha blocking effects.
- Peripheral effects include - dry skin/mouth, mydriasis, tachycardia, urinary retention, ileus, raised temperature (more connomly seen in children).
- Central effects include - confusion, picking movements, agitation, aggression, delirium, sedation, hallucination (mainly visula), seizure (less frequently)
