Anticholinergic Drugs Flashcards
1
Q
Three types of anticholinergic drugs?
A
- Muscarinic blockers
- anticholinergic primarily refers to muscarinic - Ganglionic blockers
- Neuromuscular blockers
- loss of specificity of receptor blocking action with large doses, causes wide range of ADRs
2
Q
Muscarinic blockers definition?
A
- inhibit cholinergic transmission at postganglionic parasympathetic receptors of smooth muscle, cardiac muscle, exocrine glands
- atropine
3
Q
Ganglionic blockers definition?
A
- block ACh cholinergic transmission at autonomic ganglia in both parasympathetic and sympathetic nerves
- nicotinic I sites
- mecamylamine
- trimethaphan
4
Q
Neuromuscular blockers definition?
A
- reduce action of ACh at synapses between nerves and skeletal muscles
- nicotinic II sites
- pancuronium
5
Q
Major pharmocological actions of anticholinergic drugs?
A
- GI
- decreased motility, constipation
- decreased secretions - CV
- tachycardia, blocks vagus nerve
- small doses of atropine can cause bradycardia - Urinary tract
- contration of sphincter muscle
- relaxation of detrusor muscle
- urinary retention - Eye
- relaxes ciliary muscle
- cycloplegia (paralysis of accommodation)
- relaxes sphincter, dilation (mydrasis) - Exocrine glands
- decrease sweating, salivation, mucous formation (nasal) - Smooth muscle
- relaxation of non vascular smooth muscle (bronchioles, intestines, uterus) - CNS
- decreased sensitivity to motion
- disorientation (blocking ACh in brain, cognitive deficit)
- decreased skeletal muscle activity
- possible hallucinations
6
Q
Belladona Alkaloids?
Atropine, Scopolamine
A
- muscarinic blocker
- dilates pupils
- relatively selective blocking action at M receptor sites
- cross BBB and interfere with cognitive function
Mechanism:
- competitive and reversible block of ACh
- large doses block cholinergic transmission
Clinical uses:
- produce mydriasis and cycloplegia for eye exam
- reduce GI motility (don’t take this if you have diarrhea from bacteria, need GI tract to increase to get rid of bacteria)
- relief of nasopharyngeal and bronchial secretions
- motion sickness
- antidote to over dose of cholinergic agents
- relief of symptoms of parkinsonism
- control extrapyramidal disorders resulting from antipsychotic meds
Absorption:
- absorbed rapidly trough GI and eye
- Scopolamine also absorbed through skin behind ear as a transdermal patch
ADR:
- dry mouth
- constipation
- tachycardia
- confusion
- drowsiness
- cycloplegia
Contraindications:
- narrow angle glaucoma
- renal obstruction
- myasthenia gravis
Interactions:
- effects increased by antihistamines, tricyclic antidepressants, antipsychotics, anti anxiety drugs, quinidine, procainamide
- action decreased by antacids
- antimuscarinics may enhance bronchodilators
- may decrease effect of cholinergic drugs
7
Q
Best treatment for Parkinsons?
A
- best is L-Dopa (precursor to Dopamine) but patients become tolerant after 5 years
- first start with anticholinergic drug to reduce symptoms for a few years before L-Dopa treatment
8
Q
Antispasmodic drugs?
A
- tertiary amines
- muscarinic blockers
- good lipid solubility (well absorbed PO)
- wide distribution
- dicyclomine
- irritable bowel syndrome - Oxybutinin
- bladder instability (urine leakage) - Tolterodine
- bladder instability (sold over counter) - Oxyphencyclimine
- peptic ulcer
9
Q
Mydriatic drugs?
A
Effects:
- tertiary amines
- muscarinic blockers
- good lipid solubility
- used to produce dilated pupils for eye exam
- treats uveitis
- Atropine
- duration 6-12 days - Hematorpine
- 1-3 days - Scopolamine
- 3-7 days - Cyclopentolate
- duration 24 hours - Tropicamide
- shortest duration of 6 hours
ADR:
- danger of systemic absorption
- disorientation
- retrograde amnesia
- hallucinations
- cardia arrhythmias (atrial fib, SVT)
- death
10
Q
Antiparkinsonian agents?
A
- tertiary compounds
- crosses BBB
- muscarinic blockers, anticholinergic
Clinical use:
- used when there is imbalance between ACh and Dopamine, in parkinson’s ACh is higher
- decrease akinesia, tremor, rigidity
- reduce excessive salivation
- extrapyramidal disorder or syndrome from antipsychotics that block Dopamine
- Benztropine
- start small and increase slowly - Trihexyphenidyl
- sustained release form, not used to initiate therapy - Diphenhydramine
- antihistamine with central anticholinergic activity
- less peripheral side effects
- sedative effect for patients with insomnia - Ethopropazine
- high degree of peripheral anticholinergic action
- less effective
ADR:
- constipation
- urinary retention
- tachycardia
11
Q
Quaternary amines?
A
- low degree of lipid solubility
- muscarinic blockers, anticholinergic
- target is GI tract, poor absorption, does not cross BBB, limited distribution
- longer duration of action
Clinical uses:
- small doses inhibits sweating
- next dose causes mydriasis, cycloplegia
- next dose decreases gastric motility, urinary tracts
- next dose decreases gastric acid secretion
- large doses cause delirium
- Clindinium
- Librax = chloradriazepoxide + Clindinium - Glycopyrrolate
- parenteral
- decrease saliva
- reduce secretions of GI and respiratory tracts
- prevent bradycardia - Methantheline
- treats hypertonic neurogenic bladder - Propantheline
- more potent than Methantheline - Ipratropium
- treats asthmas, inhalation - Tiotropium
- treats asthma, bronchodilation duration longer than Iprotropium
- additive with sympathomimetics in patients with severe airflow obstruction
- better in COPD than asthma
- use alternatives for patients not tolerating Beta 2 agonists
12
Q
Ganglionic blocking depolarizing drugs?
A
Depolarizers
-so much stimulation it overwhelms the site and it shuts down, prevents repolarization
- Nicotine (alkaloid)
Effects:
- elevates BP by increasing adrenal medulla to release NE and Epi
- increased HR
- increased GI motility, diarrhea
- CNS stimulation
- increased respiration
- used as smoking deterrent
ADR from extremely large doses:
- reduced BP
- increased HR (tachycardia), irregular
- confusion
- convulsions
- respiratory failure
Treatments: gastric lavage
13
Q
Ganglionic blocking non depolarizing drugs?
A
Nondepolarizers
- decrease depolarization, cell cannot fire
- blocks ACh at post synaptic sites in ganglia ANS
- nonselective blocking action, reduces neurotransmitter
Interference with sympathetic impulse:
- marked vasodilation, orthostatic hypotension
- decreased venous return, decreased CO
Interference with parasympathetic impulse:
- decreased GI motility and secretions
- dry mouth
- urinary retention
- constipation
- cycloplegia and mydriasis
- impotence
- Mecamylamine
- Trimethaphan
14
Q
Mecamylamine?
A
- non depolarizing ganglionic blocker
- secondary amine, good absorption
Effect:
- no depolarization
- prolonged lowering of BP (6-12 hours)
- postural hypotension
Clinical uses:
-management of moderate severe to severe hypertension and uncomplicated malignant hypertension when other drugs have failed
ADR:
- anticholinergic
- lost control of bladder and bowels
Contraindications:
-coronary insufficiency and recent MI
Precautions:
- avoid termination of therapy
- hypertensive rebound
- cerebrovascular accident (CVA)
- withdraw slowly while other antihypertensives are substituted
15
Q
Trimethaphan?
A
- non depolarizing ganglionic blocker
- short duration of action (10-30 mins after IV)
Effect:
- may produce direct relaxant action on vasoconstriction of smooth muscle
- release of histamine
- rapid return of BP within 10 minutes of terminating infusion
Clinical use:
- produce controlled hypotension during surgery (reduce hemorrhage)
- acute control of BP in hypertensive emergencies
- controlling BP in cases of acute dissecting aortic aneurysm
