Jacob Hummel M.D.

Tulane University Anesthesiology

Anticholinergics

*Objectives

*Know the different mechanisms of action for atropine, scopolamine and glycopyrrolate

*Clinical use of each of these drugs

*Effects on the cardiovascular, respiratory, cerebral, G.I. and other organ systems

*Disclosures

*This is a really short lecture but its brevity does not reflect the value of its content

*Antimuscarinics

*This term is more indicative of what these drugs accomplish as they are primarily blocking the effects of acetylcholine at the muscarinic receptors

*Antimuscarinics

*Primary use is prior or concomitant administration with anticholinesterases

*Crucial in the treatment of bradycardia

*Beneficial in the prevention of PONV

*Antisialogogues

*The Antimuscarinics

*

*Structure and Binding

*Ester linkage essential for effective binding to the acetylcholine receptors, competitively inhibiting the binding of acetylcholine

*Different types of muscarinic receptors: neuronal (M1), cardiac (M2), and glandular (M3)

*Systemic Effects

*CARDIOVASCULAR

*Blockade of the muscarinic receptors in the sinoatrial node results in tachycardia

*Useful for reversing vagal reflexes

*Systemic Effects

*RESPIRATORY

*Inhibit secretions along the respiratory tract

*Relaxes bronchial smooth muscle ->

decreased airway resistance but increased dead space

*Systemic Effects

*CEREBRAL

*Range of effects, stimulation to depression

*Physostigmine reverses these occurrences

*Systemic Effects

*G.I.

*Decreased secretions and salivation

*Decreased peristalsis

*Lower esophageal sphincter pressure reduced

…better view, but more at risk for aspiration

*Systemic Effects

*Other Effects

*Mydriasis

*Urinary retention

*Reduced sweating, rise in body temp

*Atropine

*Potent effects on the heart and lungs

*Most efficacious for treating bradycardia

*Tertiary amine allows it to cross blood-brain barrier

*Derivative is ipratropium bromide and used to treat bronchospasm

*Use cautiously with heart disease, narrow angle glaucoma, BPH and bladder-neck obstruction

Give me the atropine, NOW!

*Scopolamine

*Similar dosing to atropine, 0.01-0.02 mg/kg with adult dose around 0.4 - 0.6 mg

*More potent antisialogogue than atropine

*Greater CNS effects

*Lipid solubility allows for the transdermal patch

*Don’t touch your eyes after you put a patch on someone!

*Glycopyrrolate

*Contains mandelic acid in place of the tropic acid seen in atropine

*Dosing is usually half of the atropine dosing and used for similar effects (bradycardia, antisialogogue, etc.)

*Quaternary structure prevents crossing of the blood-brain barrier

*No ophthalmic activity

*Potent antisialogogue

*Longer duration of action than atropine (2-4 hrs. vs 30 minutes)

*Case Discussion

*An elderly patient is scheduled for enucleation of a blind, painful eye. Scopolamine, 0.4 mg intramuscularly, is administered as premedication. In the preoperative holding area, the patient becomes agitated and disoriented

The only other medication the patient has received is 1% atropine eye drops

*…how do you treat and would you proceed with the case?

*Anticholinergic Poisoning

*Signs and Symptoms

*Agitation, delirium, unconsciousness

*dry mouth, tachycardia, atropine flush, atropine fever, and impaired vision

…antidote is physostigmine as it is the only anticholinesterase to cross the blood-brain barrier

*Proceed with the case?

*Elective Procedure

*Is patient optimally medically managed?

*Do symptoms resolve with intervention?

*Thanks for your attention

*GENERAL HUMMEL FROM ALCATRAZ….OUT!

*References