Muscarinic and nicotinic blockers Flashcards by Jessica A

Nicotinic receptor agonists. Examples

Nicotine
Acetylcholine
Choline
Epibatidine
Lobeline
Varenicline
Cytisine

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Natural nicotinic agonists (selective)

Nicotine(small doses)
Lobeline

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Synthetic Nicotinic Agonists (selective)

Dimethyl phenyl piperazinium (DMPP)
Tetra methyl ammonium (TMA)

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Excessive amounts of selective nicotinic agonists leads to

Sustained depolarization
Ganglion block

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Non-selective muscarinic agonists

ACh
Pilocarpine
Carbachol
Anti-ChE

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Nicotine is what type of amine and is derived from

Tertiary
Nicotiana tobacum leaves

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Overall effects of GANGLIONIC stimulation on Blood vessels (sympathetic)

Vasoconstriction
Hypertension
Reduced peripheral blood flow

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Effects of Ganglionic stimulation in the heart, GIT, Eye, UT, salivary gland

Same as Parasympathetic
Bradycardia, Increased tone, Miosis, Urination, watery salivation

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Effect of ganglionic stimulation on sweat gland

Increased sweating (sympathetic)

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Nicotine is available as transdermal patches for

Treating nicotine dependence

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Varenicline :

Partial agonist
Reduces craving for and pleasurable effects of cigarettes

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Vesamicol

Inhibits ACh carrier (Vesamicol inhibits acetylcholine uptake in presynaptic vesicles and reduce its release)

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Botulinum

Presynaptic toxin that inhibits exocytosis of ACh from vesicles

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Tubocurarine

Non-Depolarizing blocking agent(at synapse). Competitive antagonist of ACh

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Suxamethonium

Depolarizing blocking agent. Inhibits the Post synaptic ACh receptor

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Neostigmine

Anticholinesterase (inhibits AChE enzyme)

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Hemicholinium

Inhibits the reuptake of choline (inhibits the choline carrier)

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Action on M1 receptor on gastric gland

Histamine release
Acid secretion

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Clinically Selective Anticholinergic Drugs (M1)

Pirenzepine
Telenzepine
Dicyclomine
Trihexyphenidyl

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Function of M2 receptor on atrium

Shortening of APD, reduced contractility

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Function of M2 receptor and on the CNS

tremor, anelgesia

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Clinically selective anticholinergic drugs (M2)

Tripitamine, Methoctramine

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Effects of M3 on visceral smooth muscle

Contraction

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Effects of M3 on vascular endothelium

Release of NO to produce vasodilation

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Clinically Selective Anticholinergic drugs (M3)

Darifenacin Solifenacin Oxybutinin Tolterodine

When activated, M4 receptors inhibit ACh release in the …………….

Striatum

Antagonist drug of M4 receptors

Himbacine

List the natural anti muscarinic drugs

1. Atropine (DL-hyoscyamine) 2. Scopolamine (L-hyoscine)

Synthetic anti muscarinic drugs are divided into

Structural analogues of atropine Structurally non related to atropine

List the tertiary ammonium compounds that are structural analogues of atropine

Homatropine

List the anti muscarinic drugs that are quarternary ammonium compounds

1. Atropine methyl nitrate (Amn) 2. Homatropine methyl bromide (Hmb) 3. Methscopolamine bromide (Mb) 4. Ipratropium 5. Tiotropium

List the Tertiary amines structurally unrelated to atropine (anti muscarinic)

1. Pirenzepine 2. Dicyclomine 3. Cyclopentolate 4. Oxyphancyclimine 5. Tropicamide

List the quarternary amines structurally unrelated to atropine (Synthetic anti muscarinic)

1. Methantheline 2. Propantheline 3. Isopropamide 4. Glycopyrrolate

List the nonselective muscarinic receptor antagonists

1. Atropine 2. Scopolamine 3. Homatropine

List the selective muscarinic receptor M1 antagonists

1. Pirenzepine 2. Telenzepine 3. Trihexyphenidyl

List the Selective Muscarinic M2 antagonists

Methoctramine

List the selective muscarinic M3 antagonists

1. Hexahydrosiladefenidol (HHSiD) 2. 4-DAMP

Selective muscarinic M4 receptor antagonists

Himbacine

What is Hyoscine derived from

Datura stramonium - THORN APPLE

Classify Homatropine

Semisynthetic Mydriatic

List the Semisynthetic antiasthmatics

Iprotropium Tiotropium bromide

List the semisynthetic GI spasmolytics

Hyoscine butyl bromide

List the synthetic mydriatics

Tropicamide Cyclopentolate

List Synthetic Quartenary GI spasmolytics

1. Oxyphenonium 2. Clidinium 3. Pipenzolate 4. Isopropamide 5. Glycopyrrolate

Classify Dicyclomine

Synthetic Tertiary GI plasmolytic

List the Synthetic Tertiary Antiulcer drugs

Pirenzepine Telenzepine *(M1-blockers)*

List the Synthetic Tertiary Vasicoselective drugs

Flavoxate Oxybutynin Tolteridine

List the Synthetic Tertiary Antiparkinsonians (central M-cholinolytics)

1. Benztropine 2. Biperiden 3. Trihexyphenidyl (benzhexol)

Salivary, Lacrimal, Bronchial and sweat glands are inhibited by very *high/low* doses of atropine

Low

In low doses, atropine causes (heart rate)

Bradycardia

Regarding the eye, Atropine causes

Mydriasis and Cycloplegia (dilatation and paralysis of accommodation)

Low doses of atropine in the CNS can cause

Mild restlessness

Higher does of atropine in the CNS can cause

Agitation and Disorientation

Central effects of atropine could be opposed by

Anticholinesterase drugs e.g Physostigmine

Low doses of Hyoscine in the CNS cause

Mild sedation

Hyoscine is useful as an Antiemetic and in motion sickness T/F

How do atropine-like drugs affect the extrapyramidal system?

By Reducing involuntary movement and rigidity in Parkinson’s disease

Atropine produces a much of anaesthetic action on the cornea T/F

How is atropine eliminated

50% eliminated in the liver. The rest excreted unchanged

Hyoscine is more completely metabolized but does not cross the BBB. T/F

F. Hyoscine crosses the BBB

Half life of Atropine

Approximately 4 hours

Effects of anti muscarinic anatagonists on the heart

Bradycardia at low doses then Tachycardia

Symptoms of anticholinergic toxicity

Hot as a hare Dry as a bone Red as a beet Blind as a bat Mad as a hatter

Management of anticholinergic toxicity

1. Cold sponges/Ice baths 2. Physical restraints 3. Chemical restraints(Benzodiazepines) 4. Gastric lavage (if ingested) 5. Physostigmine (1-3)mg

Physostigmine arrests both central and peripheral effects. T/F

Neostigmine affects only central effects. T/F

F. Neostigmine is ineffective for central effects

Clinical uses of Anticholinergics

1. As antisecretory 2. As antispasmodic 3. Bronchial asthma, COPD 4. As mydriatic and cycloplegic 5. As cardiac vagolytic 6. For central action (Parkinsonism, Motion Sickness, Sedation and Amnesia) 7. Antidote (Anti ChE, early mushroom poisoning)

…………,,,,, is used to produce sedation and amnesia in labour and maniacal states

Hyoscine

Atropine *delays/stimulates* gastric emptying and absorption of other drugs

Delays

…….. interferes with absorption of anticholinergics

Antacids

Other drugs that have anticholinergic properties

Antihistamines Tricyclic antidepressants Phenothiazines Disopyramide Pethidine

Antinicotinic drugs are divided as

Ganglion blockers Neuromuscular blockers

Examples of ganglion blockers

Hexamethonium Trimetaphan Mecamylamine (MTH GANG)

Examples of neuromuscular blockers

Suxamethonium Decamethonium Tubocurarine Atracurium

All ganglion blockers of interest are

Synthetic amines

List the Competitive ganglion blockers

Hexamethonium Mecamylamine Trimethaphan

List the Non-competitive ganglion blockers

Nicotine (large doses) Acetylcholinesterases (large doses)

Effect of Ganglion blockade on the heart

Tachycardia

Trimethaphan is occasionally used in

Treatment of hypertensive emergencies

Effects of ganglion blockade

Depression, vasodilation, hypotension, Decreased VR, tachycardia, Decreased tone and motility

Action of NM blockers

Block NM transmission at the NMJ, causing paralysis of the affected skeletal muscles

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Muscarinic and nicotinic blockers Flashcards

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