phramacology Cholinergic antagonists
Terms
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- cholinergic antagonists
- block the action of Ach at muscarinic receptors
- tertiary agents
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lipid soluble
penetrates CNS better - quarternary agents
-
positive charge
water soluble
have higher ganglionic blocking to antimuscarinic activity ratio - Atropine
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from belladonna plant
prototype of its class - Scopolamine
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Transderm Scop
L-hyoscine
(tertiary cholinergic antagonist) - Ipratropium
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Atrovent
structually similar to Atropine, but its quat - drug classes with anticholinergic effects
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H1-blockers
phenothiazines
TCA's
carbamazepine (Tegretol) - anticholinergic toxicity symptoms
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1) hot as a hare, hyperthermia
2) blind as a bat (mydriasis & cycloplegia)
3) mad as a hatter (CNS stimulation)
4) dry as a bone (xerostomia) - other anticholinergic Side effects
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tachycardia
constipation
mental confusion
urinary retention -
cholinergic antagonists
tertiary agents -
1) Atropine
2) Scopolamine
3) Benztropine mesylate
4) Trihexyphenidyl
5) Dicyclomine
6) Darifenicin
7) Homatropine
8) Cyclopentolate
9) Tropicamide - L-hyoscyamine
- active form
- d-hyocyamine
- non-active form
- use of Atropine
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1) treat bradycardia
2) pre-op to decrease secretions
3) mydriatic for eye exam
4) counteraction for AchE-I toxicity
** No longer used for Parkinson's** - action of Atropine
- competitive inhibitor at autonomic postgang. cholinergic receptors (muscarinic) even in sympathetic systems at sweat glands
- Atropine at low doses
- paradoxical decrease in HR
- Atropine at higher doses
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restlessness
hallucinations
disorientation - Scopolamine vs Atropine
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Scopolamine: more potent than Atropine on iris, ciliary body, secretions
less potent: at heart, bronchial & GI smooth muscles - Scopolamine at therapeutic doses
- high incidence of CNS depression
- use of Scopolamine
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to prevent motion sickness (most common)
treatment for Parkinsonism - Scopolamine in WW2
- twilight sleep and lowers inhibitions
- Benztropine mesylate
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Cogentin
synthetic muscarinic antagonists (structure similar to Atropine
tertiary agent - use of Benztropine mesylate
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used to treat Parkinsonian syndromes
extrapyramidal symptoms
antihistaminic
local anesthetic effects - Benztropine mesylate blocks?
- blocks CNS muscarinic receptors (M1) and dopamine reuptake
- Trihexyphenidyl
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Artane
synthetic antimuscarinic
tertiary agents - use of Trihexyphenidyl
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for Parkinsonism
blocks dopamine reuptake
direct antispasmodic action on smooth muscles - Dicyclomine
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Bentyl
cholinergic antagonist
tertiary agents (but little CNS activity) - use of Dicyclomine
- antispasmodic in Tx of IBS
- Darifenicin
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competitive agent
more potent at M3 receptors - use of Darifenicin
- used to tx overactive bladder and urgency
- Darifenicin bind to?
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alpha-1-acid glycoprotein
98% plasma protein bound - major eliminate route of Darifenicin?
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P-450 metabolism (CYP2D6 & CYP 3A4)
**caution in hepatic insufficiency or with P-450 inhibitors** - mojor SE of Darifenicin
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dry mouth
dry eyes
constipation
UTI's - Homatropine
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Isopto Homatropine
cholinergic antagonist
tertiary agent - use of Homatropine
- opthalmic to produce mydriasis and cycloplegia for Dx
- contraindication of Homatropine
- pt with glaucoma or sensitivity to anticholinergics
- Cyclopentolate
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Cyclogyl
cholinergic antagonist
tertiary agent - use of Cyclopentolate
- ophthalmic to produce mydriasis and cycloplegia for dx
- Tropicamide
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Mydriacyl
cholinergic antagonist
tertiary agent - use of Tropicamide
- opthalmic to produce mydriasis and cycloplegia for dx
- contraindication of Tropicamide
- pt with glaucoma or a sensitivity to anticholinergics
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Homatropine
Cyclopentolate
Tropicamide - may cause temporary stinging/burning on application, and increase IOP
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cholinergic antagonists
quaternary agents -
1) Glycopyrrolate
2) Ipratropium
3) Propantheline - Glycopyrrolate
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Robinal
quaternary agent
cholinergic antagonist - use of Glycopyrrolate
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GI antispasmotic
tx of bronchospasm
pre-op med to decrease salivary, GI, & pulmonary secretions
to decrease risk of acid aspiration during sx - use of Glycopyrrolate during sx
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to block the effect of vagal stimulation
to block the muscarinic stimulation seen when anticholinesterase are used as reversal agents - Glycopyrrolate, any CNS effects?
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No CNS effects
should not be used to tx OP toxicity - use of Ipratropium
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bronchodialator for COPD
for acute asthma attacks
rinorrhea - Proantheline
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Pro-Banthine
quat
older drug, used infrequently now - use of Proantheline
- duodenal ulcers and IBS
- absorption of Proantheline
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absorption incomplete (10-25%) and variable
food further decreases absorption