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Questions and Answers
Which of the following is a reason Ach is not used clinically?
Which of the following is a reason Ach is not used clinically?
What condition is NOT treated by the use of carbamylcholine?
What condition is NOT treated by the use of carbamylcholine?
Which of the following adverse effects is associated with muscarinic receptor stimulation?
Which of the following adverse effects is associated with muscarinic receptor stimulation?
What is a distinguishing feature of pilocarpine compared to other muscarinic agents?
What is a distinguishing feature of pilocarpine compared to other muscarinic agents?
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Which reversible anticholinesterase has the shortest duration of action?
Which reversible anticholinesterase has the shortest duration of action?
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Which action differs between physostigmine and neostigmine?
Which action differs between physostigmine and neostigmine?
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What is an important use for neostigmine?
What is an important use for neostigmine?
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Which condition is effectively managed using methacholine?
Which condition is effectively managed using methacholine?
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Which irreversible anticholinesterase has a duration of action lasting days to weeks?
Which irreversible anticholinesterase has a duration of action lasting days to weeks?
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What is NOT a common adverse effect of cholinomimetics?
What is NOT a common adverse effect of cholinomimetics?
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What is a clinical use of muscarinic agents like carbachol or bethanechol?
What is a clinical use of muscarinic agents like carbachol or bethanechol?
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Which adverse effect is predominantly associated with the action of M3 muscarinic receptors?
Which adverse effect is predominantly associated with the action of M3 muscarinic receptors?
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What differentiates neostigmine from physostigmine?
What differentiates neostigmine from physostigmine?
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In the context of cholinomimetics, which condition is effectively treated with pilocarpine?
In the context of cholinomimetics, which condition is effectively treated with pilocarpine?
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Which of the following substances is classified as an irreversible anticholinesterase?
Which of the following substances is classified as an irreversible anticholinesterase?
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What is a significant therapeutic use for methacholine?
What is a significant therapeutic use for methacholine?
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Which characteristic does not apply to the effects of pilocarpine?
Which characteristic does not apply to the effects of pilocarpine?
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Which of the following statements about reversible anticholinesterases is true?
Which of the following statements about reversible anticholinesterases is true?
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Which statement is correct regarding the duration of action for short-acting anticholinesterases?
Which statement is correct regarding the duration of action for short-acting anticholinesterases?
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Which of these cholinergic agents is known to stimulate nicotinic receptors directly?
Which of these cholinergic agents is known to stimulate nicotinic receptors directly?
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Study Notes
Ach - Clinical Uses
- Ach is not commonly used clinically due to its short duration of action and lack of selectivity
- Bethanacol and carbachol are used to treat postoperative urinary retention and paralytic ileus in the absence of mechanical obstruction
- Carbachol and bethanechol used as eye drops for the treatment of glaucoma
- Methacholine is indicated for treatment of peripheral vascular diseases as a vasodilator
- Methacholine is also used to relieve attacks of paroxysmal atrial tachycardia
Adverse Effects of Parasympathomimetics
- Adverse effects include nausea, vomiting, diarrhea, sweating, salivation, colic, involuntary urination and defecation, bronchial constriction, and decreased blood pressure (due to M3 receptors)
- Bradycardia is an adverse effect related to the stimulation of M2 receptors
Pilocarpine - Naturally Occurring Alkaloid
- Pilocarpine is muscarinic acting and does not have nicotinic effects
- Specific action on the eye, but no eye lid twitches (no nicotinic action)
- Pilocarpine increases salivary and sweat secretions
- Uses include treatment of glaucoma and promoting hair growth
Indirect Acting Cholinergic Drugs:
- Indirect acting cholinergic drugs work by inhibiting cholinesterase
Reversible Anticholinesterase
- Short-acting anticholinesterase: duration of action 5-10 minutes, e.g., Edrophonium.
- Medium-duration anticholinesterase: duration of action 2-6 hours, e.g., physostigmine, neostigmine, donepezil.
Irreversible Anticholinesterase
- Irreversible anticholinesterase (organophosphates): duration of action days-weeks, e.g., di-isopropyl-fluorophosphate (DFP).
Differences Between Physostigmine and Neostigmine:
- Physostigmine is a natural alkaloid, while neostigmine is synthetic
- Physostigmine has good oral absorption, while neostigmine has poor oral absorption
- Physostigmine has CNS action, while neostigmine does not have CNS action
- Physostigmine has no direct action on muscular nicotinic receptors, whereas neostigmine has prominent effect on skeletal muscle
- Physostigmine has prominent effect on autonomic effectors, while neostigmine has less effect on autonomic effectors
- Physostigmine's important use is as a miotic, while neostigmine is used primarily in the treatment of Myasthenia Gravis
- The duration of action in eyes is 6-24 hours for physostigmine, while the systemic duration is 4-6 hours
- Neostigmine has a duration of action of 3-4 hours
Ach (Acetylcholine)
- Not used clinically due to short duration of action and lack of selectivity.
Parasympathomimetics
- Used for relief of postoperative retention of urine and paralytic ileus in the absence of mechanical obstruction
- Examples: Bethanechol, Carbachol
Glaucoma
- Carbachol and Bethanechol are used as eye drops for glaucoma.
Vasodilator
- Methacholine is used as a vasodilator in the treatment of peripheral vascular diseases
Paroxysmal Atrial Tachycardia
- Methacholine used to relieve attacks of paroxysmal atrial tachycardia
Adverse Effects
- Nausea, vomiting, diarrhea
- Sweating, salivation, colic, involuntary urination and defecation
- Bronchial constriction, decreased blood pressure (M3)
- Bradycardia (M2)
Naturally Occurring Alkaloids (Pilocarpine)
- Muscarinic action, no nicotine action
- Increased salivary and sweat secretions
- Specific action on eye but no eyelid twitches due to no nicotinic action
- Used for glaucoma and promoting hair growth
Indirect Acting Cholinergic
- Reversible anticholinesterase:
- Short-acting: Edrophonium (duration 5-10 minutes)
- Medium-duration: Physostigmine, Neostigmine, Donepezil (duration 2-6 hours)
- Irreversible anticholinesterase (organophosphates): DI-isopropyl-fluorophosphate (DFP) (duration days to weeks)
Differences between Physostigmine and Neostigmine
- Source: Physostigmine is a natural alkaloid, while Neostigmine is synthetic.
- Oral absorption: Physostigmine has good oral absorption while Neostigmine has poor oral absorption.
- CNS action: Physostigmine has CNS action whereas Neostigmine does not.
- Direct action on muscular nicotinic receptors: Physostigmine has no direct action on muscular nicotinic receptors, Neostigmine does.
- Prominent effect on: Physostigmine's prominent effect is on autonomic effectors; Neostigmine's prominent effect is on skeletal muscle.
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Important use: Physostigmine is importantly used for treating myosis (contraction of pupil) and Neostigmine's important use is for myasthenia gravis.
-Duration of action:
- Physostigmine duration of action varies depending on the route of administration. Systemic duration of action is 4-6 hours; in eye, it's 6-24 hours.
- Neostigmine has a systemic duration of action of 3-4 hours, and is not used in the eye.
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Description
Explore the clinical applications of acetylcholine and its derivatives, including bethanechol and carbachol, in treating various conditions. This quiz also covers the adverse effects of parasympathomimetics and the specific actions of pilocarpine. Test your knowledge on the uses and impacts of these pharmacological agents.
