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Pharmacology Test 1 Material > Cholinergics > Flashcards

Cholinergics Flashcards

1
Q

Where are Cholinergic receptors found?

A
  • Nicotinic (N1/Nm) found on Skeletal Muscle
  • Nicotinic (N2/Nn) found on post-ganglionic neurons of the ANS (both sympathetic and parasympathetic)
  • Muscarinic (M1-M3) found on parasympathetic end organs
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2
Q

Are Nicotinic receptors G-coupled protein receptors or Ligand-gated receptors? Describe the appropriate receptor type.

A

Nicotinic Ligand-gated receptors: Bind 2 ACh molecules causing Na+ channel to open and causing Excitatory Postsynaptic Potential (EPP) to be evoked and Action Potential generated when threshold reached

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3
Q

Are Muscarinic receptors G-coupled protein receptors or Ligand-gated receptors? Describe the appropriate receptor type.

A

Muscarinic G-coupled protein receptors
M1 and M3 receptors are Gq receptors: leads to release of Ca2+ and Contraction of smooth muscle/glands
M2 receptor is a Gi receptor (inhibitory): inhibition of cAMP leads to decreased heart function

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4
Q

What is the rate limiting factor in ACh synthesis?

A

Choline uptake

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5
Q

What enzyme catalyzes the synthesis of ACh?

A

Choline Acetyltransferase (ChAT)

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6
Q

What enzyme inactivates ACh in the synaptic cleft?

A

Cholinesterase (ChE): Acetylcholinestase and Plasma Cholinesterase (aka Pseudocholinesterse)

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7
Q

What class of drugs are seen below?
Bethanechol
Methacholine
Carbachol

A

Cholinergic Agonists: Directly stimulates the PNS

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8
Q

Bethanechol

1) Receptor targeted?
2) Susceptible to Cholinesterase?
3) Use?

A

1) Muscarinic Selective
2) NO=Longer Half-life
3) Post-op ileus, Congenital megacolon, Urinary retention

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9
Q

Methacholine

1) Receptor targeted?
2) Susceptible to Cholinesterase?

A

1) Muscarinic Selective

2) YES=Shorter Half-life

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10
Q

Carbachol

1) Receptor targeted?
2) Susceptible to Cholinesterase?
3) Use?

A

1) Non-selective, activates Muscarinic and Nicotinic
2) NO=Longer Half-life
3) Glaucoma

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11
Q 
What class of drugs are seen below?
Muscarine
Pilocarpine
Nicotine
Varenicline
A

Natural Alkaloid Cholinergic Agonists: Directly stimulate the PNS

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12
Q 
Which of the following are muscarinic selective? Which are nicotinic selective?
Muscarine
Pilocarpine
Nicotine
Varenicline
A

Muscarine, Pilocarpine=Muscarinic Selective

Nicotine, Varenicline=Nicotinic Selective

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13
Q

Pilocarpine

1) Uses
2) Mechanism of Action

A

1) Dry Mouth, Acute cases of Glaucoma

2) Cholinergic Agonist- Muscarinic receptor selective to stimulate the PNS

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14
Q

Does Nicotine stimulate the Sympathetic or Parasympathetic Nervous System?

A

Stimulates BOTH via Nn receptors on the postganglionic neurons

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15
Q

Varenicline

1) Uses
2) Mechanism of Action

A

1) Quit Smoking

2) Cholinergic Agonist- Nicotinic receptor selective

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16
Q

Describe the signs/symptoms of Cholinergic Toxicity

A

N/V/D, Urinary Urgency, Salivation, Sweating, Skin vasodilation (Flushing), Bronchial constriction

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17
Q

In what patients would Cholinergic Agonists be contraindicated?

A

Asthma, Coronary Insufficiency, Peptic Ulcer Disease, Hyperthyroidism

18
Q

Where is Acetylcholinesterase primarily located?

A

Neuromuscular junctions

19
Q

Where is Plasma cholinesterase primarily located?

A

Plasma and Liver

20
Q

Name the Competitive Cholinesterase Inhibitors.

What is their Mechanism of Action?

A

-Edrophonium (VERY short acting)
-Neostigmine
-Pyridostigmine
-Physostigmine
MOA: binds REVERSIBLY to the active site on Cholinesterase to indirectly stimulate the PNS (SHORT/Moderate-acting)

21
Q

What are some common uses of Cholinesterase INhibitors?

A

Myasthenia Gravis, Ileus, Glaucoma

Neostigmine used for neuromuscular blockade reversal

22
Q

Name the Non-Competitive Cholinesterase Inhibitors.

What is their Mechanism of Action?

A

-Organophosphates: Diisopropylfluorophosphate (DFP), Echothiophate
-Insecticides: Carbaryl, Malathion, Parathion
-Nerve Gases: Sarin, Soman
MOA: IRREVERSIBLY phosphorylates the active site on Cholinesterase causing “aging” and indirectly stimulating the PNS (LONG-acting)

23
Q

Organophosphate Intoxication can lead to ______ ___.

A

Cholinergic Crisis

  • Think ‘SLUD’-Salivation, Lacrimation, Urination, Defication
  • Also causes Bradycardia, Bronchoconstriction, Miosis
24
Q

What therapy is used for Organophosphate Intoxication?

A

1st: Atropine (Muscarinic Antagonist)- competitively binds Muscarinic receptors
2nd: Pralidoxime [aka 2-PAM] (AChE Re-activator)- MUST be given before AChE “aging” occurs

25
Q

What is the Mechanism of Action of Cholinergic Antagonists?

A

MOA: Competitively bind Muscarinic receptors blocking ACh from binding to Muscarinic receptors
*Therefore inhibiting the PNS (leads to Sympathetic symptoms/actions)

26
Q

How are these drugs related? What is their Use?
Atropine
Homotropine
Tropicamide

A
  • Cholinergic Antagonists
  • Eyes: Mydriasis (Pupil Dilation), Cycloplegia (Far Vision)- Used for Eye Exams, Eye Inflammation
  • Think about Sympathetic (Flight/Fight) Functions*
  • ALL are tertiary amines=able to cross the BBB*
27
Q

How are these drugs related? What is their Use?
Glycopyrrolate
Ipratropium
Tiotropium

A
  • Cholinergic Antagonists
  • Lungs: Decreased Secretions, Bronchodilation- Used to lessen bronchial secretions and laryngospasm before inhalant anesthetics
28
Q

How are these drugs related? What is their Use?
Atropine
Glycopyrrolate

A
  • Cholinergic Antagonists
  • Heart: Block Vagal Response, Prevent Bradycardia
  • GI: Decrease Smooth Muscle motility and GI secretions- Used for Peptic Ulcer Disease, Diarrhea d/t diverticulitis
  • Atropine NO longer used for GI d/t CNS effects w/high doses*
29
Q 
How are these drugs related? What is their Use?
Darifenacin
Oxybutynin
Tolterodine
Solifenacin
A
  • Cholinergic Antagonists
  • GU: Relaxes Smooth Muscle of the Bladder- Used for Bladder Spasms, Mild Inflammation, Neurologic condition
  • M3 receptor Selective
30
Q

How are these drugs related? What is their Use?
Trihexyphenidyl
Scopalamine
Methscopalamine

A
  • Cholinergic Antagonists
  • CNS: Anti-Parkinsonism, Anti-Motion Sickness
  • Trihexyphenidyl (Parkinson’s) and Scopalamine (Motion Sickness)=Tertiary amines= Crosses BBB(CNS effects)
  • Methscopalamine is Quanternary=NO crossing BBB
31
Q

What are the Central side effects of Cholinergic Antagonists?

A

Hallucinations, Amnesia, Sedation, Excitement

  • Only occur in tertiary amine agents*
  • THINK of Sympathetic effects*
32
Q

What are the Peripheral side effects of Cholinergic Antagonists?

A

Excessive Mydriasis (Pupil dilation), Cycloplegia (Far vision), Photophobia, Dry eyes, Dry mouth (Xerostomia), Tachycardia, Red Skin (aka “atropine fever” d/t reduced sweating)

33
Q

True/False

Ganglionic Nicotinic Agonists stimulate the Sympathetic Nervous System.

A

FALSE, Ganglionic Nicotinic Agonists stimulate both Sympathetic and Parasympathetic Nervous System.

  • The organ system determines which ANS division (Sympathetic or Parasympathetic) will give the predominate actions/functions.
  • For example, the heart is predominately controlled by the SNS, therefore the actions/functions produced by the drug will be sympathetic in nature. (Except HR, that is controlled by PNS/Vagal Nerve)
34
Q

Name one Ganglionic Nicotinic Agonist

A

Nicotine: binds to Nn receptors at ALL ganglionic sites (PNS and SNS), even the adrenal medulla
*Has MANY side effects

35
Q

Describe the Symptoms of Nicotine Toxicity

A

Nausea, excessive Salivation, Abdominal Pain, Diarrhea, Cold Sweats, HTN, Dizziness
Possible seizures, respiratory arrest (d/t muscle paralysis), and cardiac arrhythmias

36
Q

Name one Ganglionic Nicotinic Antagonist

A

Mecamylamine: non-depolarizing competitive antagonists that bind irreversibly to Nn receptors at ALL ganglionic sites
Uses: HTN emergencies, Severe PVD
**NOT 1st choice therapy d/t MANY side effects
*The organ system determines which ANS division (Sympathetic or Parasympathetic) will be blocked and give the predominate actions/functions of that division

37
Q

Transmission of action potentials at the neuromuscular junction can be facilitated/improved by ________ ____.

A

Acetylcholinesterase Inhibitors (like Neostigmine)

38
Q

True/False
Denervation of skeletal muscle results in muscle atrophy, while denervated smooth muscle does not result in muscle atrophy.

A

TRUE

39
Q

Describe the Mechanism of Action of Non-Depolarizing Neuromuscular Antagonists.

A

Competes w/ACh for binding to Nm receptors, blocks Na+ channel opening inhibiting depolarization of the muscle cell

  • Starts with motor weakness until total paralysis occurs
  • AChE inhibitors will allow ACh to compete off the non-depolarizing agent
40
Q

Name 4 Non-Depolarizing Neuromuscular Antagonists

A

CURare
CisatraCURium
MivaCURium
RoCURonium*Vagal blockade, be careful of tachycardia
**ALL are contraindicated in Myasthenia gravis

41
Q

Succinylcholine

1) Mechanism of Action
2) Use
3) Metabolizing Agent
4) Contraindications

A

1) Depolarizing Neuromuscular Antagonist- act non-competitively at Nm receptors, opening Na+ channels, depolarization occurs (Phase 1), membrane unable to repolarize initially but w/prolonged exposure membrane repolarizes (Phase 2) but is now resistant to depolarization d/t desensitization
2) Muscle Relaxant, Adjunct for Anesthesia
3) Rapid hydrolysis by Plasma Cholinesterase
4) Plasma Cholinesterase gene mutations (causes prolonged action), Conditions of high K+ (depolarization of skeletal muscle releases LOTS of K+ and risk for cardiac arrest)

Pharmacology Test 1 Material (9 decks)

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