Cholinergic Antagonists
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Questions and Answers

Which drug produces mydriasis for 24 hours?

  • Benztropine
  • Trihexyphenidyl
  • Cyclopentolate (correct)
  • Tropicamide

    • What is the primary action of antimuscarinic agents like oxybutynin in the bladder?

  • Reducing bladder capacity
  • Enhancing the frequency of bladder contractions
  • Competitively blocking M3 receptors (correct)
  • Increasing intravesical pressure

    • Which antimuscarinic agent is relatively more selective for M3 muscarinic receptors?

  • Oxybutynin
  • Tolterodine
  • Darifenacin (correct)
  • Fesoterodine

    • What are benztropine and trihexyphenidyl primarily used for?

    <p>Adjuncts with other antiparkinson agents</p> Signup and view all the answers

    Which type of receptor do antimuscarinic agents mainly block to cause adverse effects?

    <p>M3 receptors</p> Signup and view all the answers

    What is the mechanism of action of antimuscarinic agents like darifenacin and solifenacin in the bladder?

    <p>Selective antagonism of M3 receptors</p> Signup and view all the answers

    Which antimuscarinic agent is thought to undergo ester hydrolysis?

    <p>Trospium</p> Signup and view all the answers

    Which antimuscarinic agent is a preferred choice in treating overactive bladder in patients with dementia due to its minimal CNS effects?

    <p>Trospium</p> Signup and view all the answers

    Which formulation of oxybutynin has a lower incidence of adverse effects compared to the immediate-release form?

    <p>Transdermal patch</p> Signup and view all the answers

    Which cytochrome P450 enzyme is primarily responsible for the hepatic metabolism of antimuscarinic agents?

    <p>CYP 3A4</p> Signup and view all the answers

    Which antimuscarinic agent is available in an extended-release formulation allowing for once-daily dosing?

    <p>Tolterodine</p> Signup and view all the answers

    Which antimuscarinic agent is contraindicated in patients with angle-closure glaucoma?

    <p>Trospium</p> Signup and view all the answers

    What is the primary effect of atropine on the eye?

    <p>Dilation of the pupil</p> Signup and view all the answers

    Why is atropine not effective for the treatment of ulcers?

    <p>It reduces hydrochloric acid production</p> Signup and view all the answers

    What is the most potent antispasmodic property of atropine and scopolamine?

    <p>Reduced gastric motility</p> Signup and view all the answers

    In patients with angle-closure glaucoma, what dangerous effect can atropine cause in the eye?

    <p>Increased intraocular pressure</p> Signup and view all the answers

    Which neuroeffector organs exhibit the greatest inhibitory effects to atropine?

    <p>Salivary and sweat glands</p> Signup and view all the answers

    What is the mechanism of action of nondepolarizing (competitive) neuromuscular blocking agents at low doses?

    <p>Overcome by administration of cholinesterase inhibitors</p> Signup and view all the answers

    At low doses, what is the predominant effect of atropine on the heart?

    <p>Decrease in heart rate</p> Signup and view all the answers

    What happens to the ability of cholinesterase inhibitors to reverse the actions of nondepolarizing blockers at high doses?

    <p>Weakened</p> Signup and view all the answers

    How do nondepolarizing blockers affect the muscle's response to direct electrical stimulation at high doses?

    <p>Completely block response</p> Signup and view all the answers

    What is the primary action of cholinesterase inhibitors like neostigmine in the context of neuromuscular blockade?

    <p>Increase ACh concentration at the NMJ</p> Signup and view all the answers

    What is the specific effect of nondepolarizing blockers at high doses on neuromuscular transmission?

    <p>Reduce transmission strength</p> Signup and view all the answers

    What is a key difference in the muscle's response to electrical stimulation between low and high doses of nondepolarizing agents?

    <p>Muscle does not respond at all to direct stimulation at high doses</p> Signup and view all the answers

    What is the mechanism of action of depolarizing neuromuscular blocking agents like succinylcholine?

    <p>Depolarizes the plasma membrane by acting like ACh</p> Signup and view all the answers

    Why does succinylcholine persist for a longer time compared to ACh at the neuromuscular junction?

    <p>It is resistant to degradation by plasma cholinesterase</p> Signup and view all the answers

    What is unique about succinylcholine among muscle relaxants?

    <p>It is resistant to plasma cholinesterase degradation</p> Signup and view all the answers

    How does succinylcholine differ from acetylcholine in terms of degradation?

    <p>Succinylcholine remains attached longer at the receptor sites</p> Signup and view all the answers

    How do genetic variants affecting plasma cholinesterase levels impact neuromuscular paralysis?

    <p>They can prolong the duration of neuromuscular paralysis</p> Signup and view all the answers

    What role does succinylcholine play at the neuromuscular junction?

    <p>It depolarizes the muscle cell by attaching to nicotinic receptors</p> Signup and view all the answers

    What is the main reason for the brief duration of action of succinylcholine?

    <p>Hydrolysis by plasma cholinesterase</p> Signup and view all the answers

    Why should succinylcholine be used cautiously or avoided in patients with electrolyte imbalances who are receiving digoxin or diuretics?

    <p>It may increase potassium release</p> Signup and view all the answers

    Which adverse effect is most concerning in burn patients or those with massive tissue damage when administered succinylcholine?

    <p>Hyperkalemia</p> Signup and view all the answers

    What is the potential consequence of succinylcholine administration in patients deficient in plasma cholinesterase?

    <p>Prolonged apnea</p> Signup and view all the answers

    Why should succinylcholine be used cautiously in patients with renal failure?

    <p>Potential for hyperkalemia</p> Signup and view all the answers

    What is the primary cause of apnea following succinylcholine administration in patients with electrolyte imbalances?

    <p>Potassium release</p> Signup and view all the answers

    Which process contributes significantly to the rapid disappearance of drug effects upon discontinuation of succinylcholine?

    <p>Redistribution in the body</p> Signup and view all the answers

    Which muscle group is typically paralyzed first when neuromuscular blocking agents are administered?

    <p>Fingers</p> Signup and view all the answers

    What is the organ-independent elimination pathway for cisatracurium mentioned in the text?

    <p>Hofmann elimination</p> Signup and view all the answers

    How do nondepolarizing neuromuscular blocking agents mainly terminate their drug action?

    <p>Quaternary amines in bulky ring structures</p> Signup and view all the answers

    What is the primary pharmacokinetic characteristic of neuromuscular blocking agents that prevents their absorption from the gut?

    <p>Quaternary amines</p> Signup and view all the answers

    Which neuromuscular blocking agent is excreted unchanged in urine according to the text?

    <p>Pancuronium</p> Signup and view all the answers

    What is the main effect of neuromuscular blocking agents on intercostal muscles?

    <p>Paralysis</p> Signup and view all the answers

    Sugammadex acts as a selective relaxant-binding agent for which two specific neuromuscular blocking drugs?

    <p><strong>Rocuronium and cisatracurium</strong></p> Signup and view all the answers

    What is the role of plasma cholinesterase in metabolizing which neuromuscular blocking agent?

    <p>Succinylcholine</p> Signup and view all the answers

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