Anticholinergics Flashcards
2 types of anticholinergics
antimuscarinics and ganglionic blockers
action of muscarinic AChR antagonists ( antimuscarinics)
interrupts parasympathetics influence in various tissues
- predominant autonomic tone is parasympathetic ( except: vasculature and sweat glands)
- blocking mAChR-> premits sympathetic influence to become predominant
- effects will be typical of sympathetic activity
how do ganglionic blockers act
antagonising the neuronal nAChRs present on the primary ganglionic cell in all autonomic ganglia ( but arent all antagonists)
- effects are sympathetic-like ( not sweat glands or vasculature) due to blocking all autonomic influence
pharm effects of prototypical anti-muscarinic atropine - on ocular a
ocular-> 1. relaxes iris sphinicter, symp tone predominates on radial muscle
- blocks accommodation -relaxes ciliary muscle-> increases tension on ligaments -> flattens lens
- inhibits lacrimation
pharm effects of prototypical anti-muscarinic atropine - on cardiac
- standard dose increase heart rate and atrioventricular conduction by blocking vagal input
- very low doses may initially decrease hr by first blocking presynaptic receptors
pharm effects of prototypical anti-muscarinic atropine - on respiratory
- bronchial smooth muscle relaxation and dilation
2. inhibit secretions
pharm effects of prototypical anti-muscarinic atropine - on GI
- decreases lower esophageal muscle tone
- relaxes GI tones, prolonging intestinal transit time
- inhibits gastric acid secretions
pharm effects of prototypical anti-muscarinic atropine - on urinary
- relaxes detrusor muscle of the bladder causing urinary retention
pharm effects of prototypical anti-muscarinic atropine - on CNS
1, atropine and scopolamine are tertiary amines
- scopolamine is more sedating than atropine
- atropine-> 1st stimulation followed by sedating effect
- high doses can cause confusion and or hallucinations
other: inhibits sweating and could possibly lead to hyperthermia-> causes cutaneous vasodilation
major clinical uses of atropine
long lasting mydriasis, pharm path to treat amblyopia, cycloplegia , sinus bradycardia and av block, decrease of salivary and respiratory secretions -> prevents airway obstruction
, intestinal spasms and pain , decrease gastric acid secretions, reversal of muscarinic or AChE inhibitor poisoning, prevention of muscarinic side effects in pts receiving AChE inhibitors and neostigmine to reverse nerve block, mixed with diphenoxylate (opioid agonist) its an anti-diarrheal
scopolamine
anti-mus
motion sickness, side effect - drowsiness
tropicamide , cyclopentolate, homatropine
anti-mus
fast but short acting mydriatic agent
may be combined with alpha adrenergic agonist
ipratropium
anti-mus
quaternary amine-> inhalled
bronchodilator
COPD
TIOTROPIUM- similar but longer acting
tolterodine
ant-mus
managment of overactive bladder ( increased freq, nocturia, incontinence)
-fewer side effects_> dry mouth and blurred vision
contraindicated for individuals w/ narrow-angle glaucoma
dicyclomine
anti-mus
releaxes intestinal smooth muscle
IBS-> symptoms
glycopyrrolate
anti-mus
- low doses preferentially inhibit secretions for preop
- prevents excessive generalized sweating
- prevention of muscarinic side effect in pt receiving neostigmine to reverse neuromuscular block
benztropine
relieve extrapyramidal symptoms in parkinson’s or in pt taking antipsychotics
adverse actions of anti-mus
dry mouth , blurred vision (mydriasis and cycloplegia) , hot, flushed skin( anhidrosis and cutaneous vasodilation) constipation difficulty in urinating, tachycardia , CNS effects : confusion, sedation, delirium
“dry as a bone, red as a beet, hot as a hare, blind as a bat, mad as a hatter”
classes of drugs which some members have antimus activity
antihistamines - diphenhydramine
antidepressants - tricyclics - amitriptyline
phenothiazine antipsychotics- chlorpromazine
depolarizing ganglionic blockers
nicotinic agonist
- act by initially activating the ganglionic nACh receptors - followed by receptor blockade resulting from persistent depolarization
- organophosphate cholinesterase inhibitors may cause some degree of depolarizing ganglionic block
nicotine
action, basic pharm effects
- stimulation of autonomic ganglia followed by ganglionic blockade ( dose-dependent)
- stim of adrenal medulla (possible significant secretion of epi)
- stim of CNS: altering response, change in respiration
symptoms of nicotine toxicity
GI-> nausea, vomiting, salivation, diarrhea
cardio-> tachy/brady, hypo/hypertension, arrhythmia
CNS-> lethargy, confusion, seizures, coma
peripheral nervous system-> diaphoresis
muscles-> tremors, fasciculations, weakness, paralysis
endocrine-> increase epi release
non-depolarizing ganglionic blockers
act by blocking nACh receptors in all autonomic ganglia
- reduce the most prominent autonomic tone in each organ
- curare compounds use in the past as NM blockers cause non-depolarizing ganglionic blocks as well
hexamethonium (C6)
antagonist at nAChR at ganglion
- 1st effective antihypertensive (not used anymore)
- poor absorption and autonomic side effects led to discontinuation of its use
mecamylamine
antagonist at nAChR at ganglion
- can be used to improve GI absorption
- recent interest in its use for tourette syndrome
effects of ganglionic blockade on and predom tone
- arterioles
- veins
- heart
- iris
- ciliary muscle
- GI tract
- urinary bladder
- salivary glands
- sweat glands
- arterioles -s-vasodilation and increase peripheral blood flow
- veins -s- dilation, peripheral pooling , decrease return decrease CO
- heart- p- tachy
- iris-p- mydriasis
- ciliary muscle-p-cycloplegia (loss of accomodation)
- GI tract-p-decrease tone and motility, constripation
- urinary bladder- p- urinary retention
- salivary glands -p-xerostomia
- sweat glands -s- anhidrosis ( cholinergic)
atropine
action
selected uses
antagonist at all mAChRs
revere muscarinic or AChE inhibitor poisoning, long lasting pupil dilation and antidiarrheal
scopolamine
action and uses
antagonist to all mAChRs
motion sickness
tropicamide
cyclopentolate
homatropine
antagonist to all mAChRs - hort acting
pupil dilation
Ipratropium
tiotropium
action and uses
antagonist at mAChRs
quaternary amine ; local action
newer alt: tiotropium
COPD
tolterodine
action and uses
antagonist at bladder mAChRs
overactive bladder
dicyclomine
action and uses
antagonist at GI mAChRs
irritable bowel
Glycopyrrolate
action and uses
antagonist at mAChR
secretion, sweating, muscarinic overshoot after cholinesterase inhibition
benztropine
action and uses
lipid soluble mAChR antagonist
extra pyramidal effects of parkinsons
mecamylamine
action and uses
antagonist at nAChR at ganglion
improves GI absorption , tourette syndrome
hexamethonium
action and uses
antagonist at nAChR at ganglion
prevents baroreceptor reflex
