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Questions and Answers
Which of the following is considered a cholinergic agent with a short duration of action?
Which of the following is considered a cholinergic agent with a short duration of action?
Which cholinergic agent has a selective action on M1 and M3 receptors?
Which cholinergic agent has a selective action on M1 and M3 receptors?
What characteristic allows tertiary amines like pilocarpine to cross the blood-brain barrier?
What characteristic allows tertiary amines like pilocarpine to cross the blood-brain barrier?
Which of the following cholinergic agents is classified as a choline ester?
Which of the following cholinergic agents is classified as a choline ester?
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Which cholinergic agent is known for having longer action due to its resistance to hydrolysis?
Which cholinergic agent is known for having longer action due to its resistance to hydrolysis?
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What is the mechanism of action of indirect acting cholinergic agents?
What is the mechanism of action of indirect acting cholinergic agents?
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What type of cholinergic agents does Carbachol belong to?
What type of cholinergic agents does Carbachol belong to?
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What is a common side effect associated with M2 receptor activation by cholinergic agents?
What is a common side effect associated with M2 receptor activation by cholinergic agents?
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Which of the following is a reversible inhibitor of acetylcholinesterase?
Which of the following is a reversible inhibitor of acetylcholinesterase?
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Which cholinergic agent's effects are primarily reflected through both muscarinic and nicotinic receptors?
Which cholinergic agent's effects are primarily reflected through both muscarinic and nicotinic receptors?
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What impact do indirect acting cholinergic agents have on acetylcholine levels in the synaptic cleft?
What impact do indirect acting cholinergic agents have on acetylcholine levels in the synaptic cleft?
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Which of the following conditions would likely be treated using carbamates?
Which of the following conditions would likely be treated using carbamates?
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Which neurotransmitter is primarily affected by indirect acting cholinergic agents?
Which neurotransmitter is primarily affected by indirect acting cholinergic agents?
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Organophosphates, as indirect acting cholinergic agents, result in which type of inhibition of acetylcholinesterase?
Organophosphates, as indirect acting cholinergic agents, result in which type of inhibition of acetylcholinesterase?
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What application do organophosphates typically have outside of medical use?
What application do organophosphates typically have outside of medical use?
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What is a characteristic effect of increased acetylcholine levels due to indirect acting cholinergic agents?
What is a characteristic effect of increased acetylcholine levels due to indirect acting cholinergic agents?
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Which of the following cholinomimetics is classified as a choline ester and is used to treat GI atony?
Which of the following cholinomimetics is classified as a choline ester and is used to treat GI atony?
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What is the primary treatment use of Acetylcholine in eye surgery?
What is the primary treatment use of Acetylcholine in eye surgery?
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Which drug is considered long-acting and is used to treat xerostomia?
Which drug is considered long-acting and is used to treat xerostomia?
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Which of the following cholinomimetics is NOT a choline ester?
Which of the following cholinomimetics is NOT a choline ester?
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What is the duration of action for Carbachol?
What is the duration of action for Carbachol?
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What are the two classes of cholinergic drugs based on their mode of action?
What are the two classes of cholinergic drugs based on their mode of action?
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Which of the following is an example of a direct acting cholinergic agonist?
Which of the following is an example of a direct acting cholinergic agonist?
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Which class of cholinergic drugs includes echothiophate?
Which class of cholinergic drugs includes echothiophate?
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What is the primary mechanism of action of direct acting cholinergic agonists?
What is the primary mechanism of action of direct acting cholinergic agonists?
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Which cholinergic agent is noted for its ability to cross the blood-brain barrier?
Which cholinergic agent is noted for its ability to cross the blood-brain barrier?
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Which of the following is a reversible AChE inhibitor?
Which of the following is a reversible AChE inhibitor?
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What are the pharmacological effects of cholinergic drugs typically associated with?
What are the pharmacological effects of cholinergic drugs typically associated with?
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What distinguishes carbamates from organophosphates?
What distinguishes carbamates from organophosphates?
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What is the primary use of Physostigmine?
What is the primary use of Physostigmine?
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Which of the following statements is correct about Neostigmine and Pyridostigmine?
Which of the following statements is correct about Neostigmine and Pyridostigmine?
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What is a common characteristic of Organophosphates?
What is a common characteristic of Organophosphates?
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Which drug is primarily used as a second-line treatment for glaucoma?
Which drug is primarily used as a second-line treatment for glaucoma?
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Which of the following best describes the lipid solubility of Neostigmine and Pyridostigmine?
Which of the following best describes the lipid solubility of Neostigmine and Pyridostigmine?
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What condition is primarily treated with Rivastigmine?
What condition is primarily treated with Rivastigmine?
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Which one of the following is a repository of reversible cholinesterase inhibitors?
Which one of the following is a repository of reversible cholinesterase inhibitors?
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What is the reason for choosing a drug that does not cross the blood-brain barrier for treating GI and bladder atony?
What is the reason for choosing a drug that does not cross the blood-brain barrier for treating GI and bladder atony?
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Study Notes
Cholinergic Drugs: Classification and Mechanisms
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Cholinergic drugs are classified as either direct-acting (agonists) or indirect-acting (acetylcholinesterase inhibitors).
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Direct-acting cholinergic agonists bind directly to cholinergic receptors, mimicking the effects of acetylcholine. These include choline esters and alkaloids.
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Indirect-acting cholinergic agents inhibit acetylcholinesterase (AChE), the enzyme that breaks down acetylcholine. This leads to increased acetylcholine levels and prolonged cholinergic effects. These include carbamates and organophosphates.
Direct-Acting Cholinergic Agonists
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Choline esters: Acetylcholine, Bethanechol, and Carbachol are examples. Acetylcholine is rapidly hydrolyzed, while Bethanechol and Carbachol are more resistant to hydrolysis, resulting in longer duration of action (30 minutes to 2 hours compared to acetylcholine’s ~30 seconds). They act on both muscarinic and nicotinic receptors and do not cross the blood-brain barrier (BBB).
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Alkaloids: Pilocarpine and Cevimeline are examples. They are more resistant to hydrolysis than choline esters (3-4 hour duration). Pilocarpine acts on M1, M2, and M3 receptors, while Cevimeline is more selective for M1 and M3 receptors, resulting in fewer cardiac side effects. Alkaloids are lipid-soluble and cross the BBB, producing central nervous system (CNS) effects.
Indirect-Acting Cholinergic Agents (Acetylcholinesterase Inhibitors)
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Carbamates (reversible inhibitors): Neostigmine, Physostigmine, Pyridostigmine, Rivastigmine, and Donepezil are examples. Neostigmine and Pyridostigmine are quaternary amines and do not cross the BBB, while Physostigmine, Rivastigmine, and Donepezil are tertiary amines that do cross the BBB.
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Organophosphates (irreversible inhibitors): Echothiophate, Malathion, Parathion, Soman, and Sarin are examples. Organophosphates form very stable bonds with AChE, leading to prolonged effects. Malathion and Parathion are pesticides, while Soman and Sarin are nerve gases.
Pharmacokinetic Properties and Clinical Uses
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Choline esters: Poor lipid solubility prevents BBB crossing; used for conditions like glaucoma, urinary retention, and GI atony. Acetylcholine is the shortest-acting.
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Alkaloids: Good lipid solubility allows BBB crossing; used for glaucoma and xerostomia (dry mouth). Cevimeline is preferred for xerostomia due to lower cardiac side effects.
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Carbamates: Duration of action varies; uses include glaucoma, myasthenia gravis (Neostigmine and Pyridostigmine), and Alzheimer's disease (Rivastigmine and Donepezil). Pyridostigmine has a longer duration of action than Neostigmine.
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Organophosphates: Very long duration of action (2-7 days), used for glaucoma as a second-line treatment. High potential for toxicity.
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Neostigmine and Pyridostigmine differ from other carbamates by not crossing the BBB. This is clinically significant because it prevents CNS side effects.
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Description
Explore the classification and mechanisms of cholinergic drugs in this quiz. Understand the differences between direct-acting agonists and indirect-acting inhibitors, along with examples of each category. Test your knowledge on the pharmacological effects and durations of action of these important medications.
