Antimuscarinic

Question 1

Atropine

Answer 1

potent drug
causes xerostomia (dry mouth)
blocks muscarinic receptors

Question 2

Dose related effects of atropine

Answer 2

0.5mg - some dryness of mouth, inhibition of sweating
2mg - marked dryness of mouth, rapid HR, dilated pupils
10mg - above symptoms more marked, ataxia, restlessness, excitement, hallucinations, delirium

Question 3

Use of atropine

Answer 3

mydriatics to dilate pupil - eye exam, torn iris, iritis, herpes infection

cyclopentolate 45 min onset; 15hr duration - longer
tropicamide 30 min onset; 4hr duration - shorter

Question 4

Antimuscarinic affects on respiratory tract

Answer 4

decrease accumulation of fluid in lungs by decreasing secretions
blocks excess vagal activity in anesthesia and surgery

Question 5

Antimuscarinic affects on GI

Answer 5

decrease GI activity
antispasmodic effect
use for IBS (mainly in women)

Question 6

Antimuscarinic in urinary incontinence (enuresis)

Answer 6

common in elderly and in children(bed wetting)
MOA: competitive blockers of muscarinic receptors
dryness of mouth and eyes limits compliance

Question 7

Atropine analogs for enuresis

Answer 7

oxybutinin - 7 times stronger than atropine; 20% dry mouth
tolterodine - more tolerable than oxybutinin (specifically for MS receptors in bladder)
solifenacin - reduced xerostomia and constipation; 24hr duration

Question 8

Antimuscarinics for bronchoconstricition

Answer 8

decrease hyperactive vagal reflex
use an ipratropium inhaler or tiotropium (last 24 hours)
both quaternary and not absorbed
no decrease in ciliary activity or drying

Question 9

True or False. Antimuscarinics can be used for bradycardia after MI

Answer 9

True

Question 10

Receptor specificity of antimuscarinics

Answer 10

atropine - non-specific; good for M2 and M3

Pirenzepine - some specificity for M1; treat peptic ulcer

Question 11

CNS effects of tertiary amine antimuscarinics

Answer 11

include atropine, scopolamine, mydriatics, and drugs of enuresis (solifenacin, tolterodine, oxybutinin)
cause restlessness, ataxia, and hallucinations
psychosis in high doses
children and elderly are susceptible

Antidote = physostigmine

Question 12

Synthetic antimuscarinic

Answer 12

quaternary ammonium = methscopolamine - use for IBS, no CNS effect

direct effect on smooth muscle = dicyclomine - use for IBS

Question 13

Precautions of antimuscarinics

Answer 13

“Dry as a bone, blind as a bat, red as a beet, mad as a hatter”

Bad heart
intestinal atony
eye infection 
lung infection 
blurred vision 
glaucoma
prostatic hypertrophy 
block sweating