Antimuscarinics Flashcards
what does atropine block
muscarinic
dose related effects of atropine: .5mg
some dryness of mouth, inhibition of sweating
dose related effects of atropine: 2mg
marked dryness of mouth, rapid HR, dilated pupils
dose related effects of atropine: 10mg
above symptoms more marked, ataxia, restlessness, excitement, hallucinations, delerium
uses of atropine type-drugs
- Mydriatics to dilate pupil
- eye-exam, inspection
- torn iris, iritis
- herpes infection to break synechiae
- onset duration cyclopentolate
- tropicamide
Antimuscarinics to decrease respiratory secretions
- preanesthetic mediation
- decrease accumulation of fluid in lungs
- block excess vagal activity in anesthesia and surgery
antimuscarinics to decrease GI activity
IBS most common side effect
“antispasmodic” effect
-irritable bowel syndrome “IBS”
-common problem especially in women (3X more common)
-spastic constipation or diarrhea
-Treat: may contain small amounts of artopine or scopolamine and a mild sedative
acetylocholine relaxes
blood vessels
antimuscarinics in urinary incontinence (enuresis)
- 30% of 4 year olds have bed wetting
- increasingly common in elderly and also occurs in children
- drugs are competitive blockers of muscarinic receptors
- drugs effective but dryness of mouth and eyes limits tolerability and compliance
Atropine Analogs for Enuresis
Oxybutinin
Tolterodine
Solifenacin
Oxybutinin
- 7 times stronger than atropine as antispasmodic but only 20% of dry mouth problem
- skin patch even more tolerable
- no effects on GI tract
Tolterodine
more tolerable than oxybutinin
Solifenacin
reduced xerostomia, constipation
- duration 24 hour
- has specificity for M3 receptors (bladder), not much effect on M2, so no effects really on the heart
Antimuscarinics for bronchoconstriction
- decreases hyperactive vagal reflex
- ipratropium inhaler-> quaternary
- tiotropium-> lasts 24 hours
- both quaternary, not absorbed
- no decrease ciliary activity; little drying
antimuscarinics for bradycardia after MI
- sinus bradycardia can occur during acute infection
- use cautiously to restore cardiac output
receptor specificity of antimuscarinics: Atropine
- relatively non-specific
- good for M2 and M3, but less effective on M1
receptor specificity of antimuscarinics: Pirenzepine
-some specificity for M1
CNS effect of teritary amine antimuscarinics
atropine scopolamine mydriatics drugs for enuresis antidote, physostigmine
effects of CNS teritary amine antimuscarinic
restlessness, ataxia, hallucinations, psychosis in high doses
-children and elderly especially susceptable
synthetic antimuscarinics
Some are quaternary ammonium: methscopolamine
-no CNS side effects
Some have direct effect on smooth muscle
-Dicyclomine
what are the precautions for using antimuscarinics
- Bad heart, vagal activity less in infants and old age
- intestinal atony (constipation, make it worse)
- eye infection
- blurred vision
- glaucoma
- prostatic hypertrophy
- block sweating
“dry as a bone, blind as a bat, red as a beet, mad as a hatter”
best selling antimuscarnic drug on the market
Solifenacin
antimuscarinic for bradycardia after an MI?
atropine
2mg of atropine does
in a young man increases heart rate 35-40 beats/min
-must be careful in someone who has a bad heart
