Cholinoceptor Blockers (Anticholinergics)

Question 1

Class: antimuscarinic (prototype)

MOA: completely blocks all M receptors

Uses: FIRST CHOICE antidote for organophosphate poisoning, mydriatic, cyclopegic, bradycardia, hypersalivation (decrease airway secretion during anesthesia)

SE: tachycardia, mydriasis, cyclopegia, skin flushing, delirium, hallucinations, urinary retention, constipation; NO EFFECT on nicotinic toxicity, notorious for causing hyperthermia; found in Atropa belladona (deadly nightshade, used to dilate and “beautify” the pupils of ancient Egyptian women)

Similar:
HOMATROPINE
CYCLOPENTOLATE
TROPICAMIDE

Answer 1

ATROPINE

Question 2

Class: antimuscarinic

MOA: completely blocks all M receptors, restores NT balance in the basal ganglia

Uses: Parkinson’s disease (reduces tremors)

SE: BOV, dry eyes, constipation, dry mouth, urinary retention

Similar:
BIPERIDEN
TRIHEXYLPHENIDYL

Answer 2

BENZTROPINE

Question 3

Class: antimuscarinic

MOA: blocks M receptors in bronchial smooth muscle, prevents vagal-stimulated bronchoconstriction

Uses: asthma, COPD

SE: dry mouth, cough, nasal dryness; more effective and less toxic than BETA-AGONISTS in patients with COPD and heart disease (doesn’t usually affect heart, less tachycardia, less arrhythmia)

Similar:
TIOTROPIUM

Answer 3

IPRATROPIUM

Question 4

Class: antimuscarinic

MOA: completely blocks all M receptors, antagonizes HISTAMINE and SEROTONIN

Uses: motion sickness, decrease GIT acid secretion

SE: drowsiness, BOV, dry eyes, constipation, dry mouth, urinary retention

Answer 4

SCOPALAMINE

Question 5

Class: antimuscarinic

MOA: completely blocks M3 receptors

Uses: IBS, minor diarrhea, decrease GIT acid secretion

SE: tachycardia, confusion, urinary retention, increased IOP; available in PO and IV forms, RELATIVELY SHORT half-life (6 hours)

Similar:
HYOSCYAMINE
GLYCOPYRROLATE

Answer 5

DICYLOMINE

Question 6

Class: antimuscarinic

MOA: slightly blocks M3 receptors, reduces DETRUSOR msucle tone

Uses: urge incontinence, post-operative spasm

SE: tachycardia, dry mouth, constipation, increased IOP, pruritis (TRANSDERMAL PATCH)

Similar:
DARIFENACIN
SOLIFENACIN
TOLTERADINE
TROSPIUM

Answer 6

OXYBUTYNIN

Question 7

Class: antinicotinic (ganglion blocker)

MOA: completely blocks Nn ACh receptors

Uses: hypertensive emergencies

SE: postural hypotension, dry mouth, BOV, constipation, sexual dysfunction

Similar:
TRIMETHAPHAN
MECAMYLAMINE

Answer 7

HEXAMETHONIUM

Question 8

Class: antinicotinic (neuromuscular blocker), NON-DEPOLARIZING

MOA: completely blocks Nm ACh receptors

Uses: skeletal muscle relaxation in surgery

SE: hypersensitivity reaction

Similar:
PANCURONIUM
ATRACURIUM
VECURONIUM
ROCURONIUM

Answer 8

TUBOCURARINE

Question 9

Class: antinicotinic (neuromuscular blocker), DEPOLARIZING

MOA: completely blocks Nm ACh receptors

Uses: skeletal muscle relaxation in surgery

SE: less hypersensitivity reaction

Answer 9

SUCCINYLCHOLINE

Question 10

3 contraindications to muscarinic blocker use

Answer 10

• infants (hyperthermia due to decreased sweating)
• acute angle-closure glaucoma
• BPH

Question 11

Drug toxicity described as:

• HOT as a hare (fever, hyperthermia)
• DRY as a bone (xerophthalmia, xerostomia, xeroderma, decreased secretions)
• RED as a beet (cutaneous vasodilation, flushing)
• BLIND as a bat (mydriasis or pupil dilatation, cyclopegia or loss of accommodation)
• MAD as a hatter (delirium, confusion, CNS toxicity)

Answer 11

atropine toxicity