Toxicology - Anticholinergics Flashcards
most common overdose that produces anticholinergic toxic
Antihistamine (particularly diphenhydramine)
oral ingestion, the onset of anticholinergic toxicity
within 1 to 2 hours
Muscarinic receptors
autonomic effector cells that are innervated by postganglionic parasympathetic nerves, on some ganglia, and in the brain, particularly the hippocampus, cortex, and thalamus
Nicotinic receptors
peripheral autonomic ganglia, at neuromuscular junctions, and also in the brain
M1
Target Organ
Autonomic ganglia
Brain
Salivary glands
Stomach
Receptor Action When Stimulated
Decreases activity in autonomic ganglia Increases salivary and gastric acid secretion
M2
Target organ
Heart
Receptor Action When Stimulated
Decreases sinus node rate and slows conduction through the atrioventricular node
Decreases the force of atrial contraction and possibly ventricular contraction
M3
Target Organ
Smooth muscle
Endocrine/exocrine glands
Iris
Receptor Action When Stimulated
Bronchospasm
Mild vasodilation
Increases saliva and gastric acid production
Constricts the pupil
M4
Target Organ
CNS
Receptor Action When Stimulated
Multiple actions
nicotinic receptors
muscle type, found at the neuromuscular junction;
the ganglion type, found in autonomic ganglia;
and two brain types found in the CNS
classic features of the anticholinergic toxidrome
Dry as a bone
- Red as a beet
- Hot as a hare
- Blind as a bat
- Mad as a hatter
- Stuffed as a pipe
Treatment of Anticholinergic Toxicity
GI decontamination
Activated charcoal
May be more effective due to the decreased GI motility
Sedation
Benzodiazepines
Decreases the risk of hyperthermia, rhabdomyolysis, and traumatic injuries
Wide-complex tachyarrhythmias
Sodium bicarbonate
Arrhythmia due to sodium channel blockade; avoid class IA antiarrhythmics (procainamide)
Cholinesterase inhibition
Physostigmine
Use for cases of severe agitation or delirium; avoid when cardiac conduction abnormalities are present (see “Treatment” section)
Physostigmine can be used in cases of severe agitation and delirium from pure anticholinergic toxicity
adult dose of physostigmine is 0.5 to 2 milligrams
0.02 milligram/kg with a maximum dose of 2 milligrams)
decrease in agitation should be apparent within 15 to 20 minutes
continuous cardiac monitoring before and during a tration of physostigmine to assess for potential bradycardia
Patients who remain asymptomatic for more than 6 hours after the first dose of physostigmine will not require repeat physostigmine dosing
Contraindications to physostigmine
asthma,
nonpharmacologically mediated intestinal or bladder obstruction,
cardiac conduction disturbances,
and suspected concomitant sodium channel antagonist poisoning
DISPOSITION AND FOLLOW-UP
Patients with more than mild symptoms, as well as those who have received physostigmine, require hospital observation until symptoms resolve or approximately 12 hours after the last dose of physostigmine
Brain
Muscarinic Effect
Complex interactions Possible improvement in memory
Anti
Complex interactions Impairs memory Produces agitation, delirium, and hallucinations Fever
