ABA Pharmacology Fundamentals 3 — Questions and Answers
Question 1: Neostigmine reverses neuromuscular blockade primarily by:
- Directly competing with rocuronium at the ACh receptor
- Inhibiting acetylcholinesterase, increasing ACh at the neuromuscular junction (Correct answer)
- Chelating rocuronium molecules in plasma
- Stimulating acetylcholine release from motor neurons
Correct answer: Inhibiting acetylcholinesterase, increasing ACh at the neuromuscular junction
Neostigmine inhibits acetylcholinesterase, preventing ACh breakdown and increasing its concentration to compete with nondepolarizing NMBAs.
Question 2: Dexmedetomidine produces its sedative and analgesic effects primarily through:
- Agonism at mu-opioid receptors
- Antagonism at NMDA receptors
- Agonism at central alpha-2 adrenergic receptors in the locus coeruleus (Correct answer)
- Potentiation of GABA-A receptor activity
Correct answer: Agonism at central alpha-2 adrenergic receptors in the locus coeruleus
Dexmedetomidine acts on alpha-2 receptors in the locus coeruleus to reduce noradrenergic output, producing sedation and analgesia without respiratory depression.
Question 3: Which statement about ketamine is correct regarding its cardiovascular effects?
- It directly depresses myocardial contractility and reduces heart rate
- It causes vasodilation by blocking calcium channels
- It indirectly stimulates the cardiovascular system by increasing sympathetic tone (Correct answer)
- It reduces systemic vascular resistance without affecting heart rate
Correct answer: It indirectly stimulates the cardiovascular system by increasing sympathetic tone
Ketamine stimulates the sympathetic nervous system, increasing catecholamine release, which raises heart rate, blood pressure, and cardiac output.
Question 4: A patient develops prolonged neuromuscular blockade after succinylcholine. The most likely cause is:
- Upregulation of ACh receptors
- Pseudocholinesterase deficiency (Correct answer)
- Malignant hyperthermia susceptibility
- Hypermagnesemia
Correct answer: Pseudocholinesterase deficiency
Pseudocholinesterase (plasma cholinesterase) is responsible for metabolizing succinylcholine; deficiency or atypical enzyme variants dramatically prolong its duration.
Question 5: Propofol's antiemetic properties are thought to be due to:
- Antagonism at serotonin 5-HT3 receptors
- Inhibition of dopamine release in the chemoreceptor trigger zone (Correct answer)
- Reduction of serotonin in the area postrema via GABA-A modulation
- Direct antihistamine effect
Correct answer: Inhibition of dopamine release in the chemoreceptor trigger zone
Propofol inhibits dopaminergic transmission in the chemoreceptor trigger zone, contributing to its antiemetic properties.
Question 6: The Hofmann elimination pathway is clinically relevant for which neuromuscular blocking agent?
- Rocuronium
- Vecuronium
- Cisatracurium (Correct answer)
- Pancuronium
Correct answer: Cisatracurium
Cisatracurium undergoes Hofmann elimination (spontaneous pH- and temperature-dependent degradation) independent of organ function, making it useful in hepatic and renal failure.
Question 7: Which factor most increases the risk of local anesthetic systemic toxicity (LAST)?
- Using a low-pKa local anesthetic
- Inadvertent intravascular injection (Correct answer)
- High protein binding of the agent
- Performing the block at low tissue pH
Correct answer: Inadvertent intravascular injection
Inadvertent intravascular injection rapidly delivers a large dose directly to the systemic circulation, bypassing tissue uptake and causing LAST.
ABA Pharmacology Fundamentals 3
Neostigmine reverses neuromuscular blockade primarily by: