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240 SEcTIoN II Pharmacology ` PHARMACOLOGY—AUTONOMIC dRUGS Pharmacology ` PHARMACOLOGY—AUTONOMIC dRUGS
Cholinomimetic Watch for exacerbation of COPD, asthma, and peptic ulcers in susceptible patients.
agents
dRUG ACTION APPLICATIONS
Direct agonists
Bethanechol Activates bladder smooth muscle; resistant to Urinary retention.
AChE. No nicotinic activity. “Bethany, call
me to activate your bladder.”
Carbachol Carbon copy of acetylcholine (but resistant to Constricts pupil and relieves intraocular
AChE). pressure in open-angle glaucoma.
Methacholine Stimulates muscarinic receptors in airway when Challenge test for diagnosis of asthma.
inhaled.
Pilocarpine Contracts ciliary muscle of eye (open-angle Potent stimulator of sweat, tears, and saliva
glaucoma), pupillary sphincter (closed-angle Open-angle and closed-angle glaucoma,
glaucoma); resistant to AChE, can cross blood- xerostomia (Sjögren syndrome).
brain barrier (tertiary amine). “You cry, drool,
and sweat on your ‘pilow.’ ”
Indirect agonists (anticholinesterases)
Donepezil, ACh. 1st line for Alzheimer disease (Dona Riva
rivastigmine, dances at the gala).
galantamine
Edrophonium ACh. Historically used to diagnose myasthenia gravis;
replaced by anti-AChR Ab (anti-acetylcholine
receptor antibody) test.
Neostigmine ACh. Postoperative and neurogenic ileus and
Neo CNS = No CNS penetration (quaternary urinary retention, myasthenia gravis,
amine). reversal of neuromuscular junction blockade
(postoperative).
Physostigmine ACh. Phreely (freely) crosses blood-brain Antidote for anticholinergic toxicity;
barrier CNS (tertiary amine). physostigmine “phyxes” atropine overdose.
Pyridostigmine ACh; muscle strength. Used with Myasthenia gravis (long acting); does not
glycopyrrolate, hyoscyamine, or propantheline penetrate CNS (quaternary amine).
to control pyridostigmine side effects.
Pyridostigmine gets rid of myasthenia gravis.
Anticholinesterase Often due to organophosphates (eg, parathion) that irreversibly inhibit AChE. Organophosphates
poisoning commonly used as insecticides; poisoning usually seen in farmers.
Muscarinic effects Diarrhea, Urination, Miosis, Bronchospasm, DUMBBELSS.
Bradycardia, Emesis, Lacrimation, Sweating, Reversed by atropine, a competitive inhibitor.
Salivation. Atropine can cross BBB to relieve CNS
symptoms.
Nicotinic effects Neuromuscular blockade (mechanism similar to Reversed by pralidoxime, regenerates AChE via
succinylcholine). dephosphorylation if given early.
Pralidoxime (quaternary amine) does not readily
cross BBB.
CNS effects Respiratory depression, lethargy, seizures, coma.
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