Autonomic Nervous System (Cholinergic, Anticholinergic, Sympathomimetics, Sympatholytics) MCQs

Pharmacology · 223 free questions with answers & explanations.

1. A patient with organophosphate poisoning is being treated with atropine. The nurse notes that the pupil size has returned to normal but the patient still has profuse bronchial secretions. What is the correct interpretation of this finding?
2. Which of the following explains why indirect-acting sympathomimetics like amphetamine lose their efficacy with repeated dosing (tachyphylaxis)?
3. A 55-year-old man on a non-selective beta-blocker develops hypoglycemia. Which feature of his hypoglycemic episode is MOST likely to be masked by the beta-blocker?
4. Phenoxybenzamine produces irreversible alpha-blockade. The clinical implication of this irreversibility compared to phentolamine is:
5. A patient receiving clonidine for hypertension abruptly stops the medication. Within 18 hours, blood pressure rises to 210/120 mmHg. The mechanism of this rebound hypertension is:
6. A patient with pheochromocytoma crisis is given an alpha-blocker before beta-blocker therapy. If beta-blocker is administered first without prior alpha-blockade, which hemodynamic consequence occurs?
7. Neostigmine reverses non-depolarizing neuromuscular blockade by inhibiting acetylcholinesterase. Which additional mechanism contributes to its neuromuscular reversal that is NOT shared by pyridostigmine?
8. A 45-year-old woman on clonidine for hypertension abruptly stops the drug. Which receptor-level mechanism explains the rebound hypertension?
9. Which statement best describes the pharmacogenomic basis for variable response to metoprolol in different patients?
10. A patient presents with miosis, bradycardia, and excessive secretions after agricultural exposure. Atropine is given in large doses. Which muscarinic receptor subtype on the heart mediates the bradycardia being treated?
11. A patient on pyridostigmine for myasthenia gravis develops a cholinergic crisis after a concurrent prescription of an aminoglycoside. The mechanism by which aminoglycosides worsen neuromuscular blockade is:
12. Pharmacogenomic testing reveals that a patient is a CYP2D6 ultra-rapid metabolizer. Which pharmacodynamic consequence is most relevant when prescribing metoprolol for hypertension in this patient?
13. A 55-year-old man with BPH and hypertension is started on tamsulosin. Unlike prazosin, tamsulosin produces minimal first-dose hypotension. The pharmacological basis for this selectivity is:
14. A patient receiving clonidine for hypertension abruptly stops the drug. The rebound hypertensive crisis that follows is mediated primarily by:
15. Among the following, which beta-blocker possesses intrinsic sympathomimetic activity (ISA) and is therefore LEAST likely to cause resting bradycardia or cold extremities?
16. Nebivolol's vasodilatory action that distinguishes it from other beta-1 selective blockers is mediated through which mechanism?
17. A patient is on an irreversible cholinesterase inhibitor. Which feature of the resulting cholinesterase inhibition is MOST important in determining the duration of toxic effects?
18. Which adrenoceptor subtype mediates the presynaptic inhibition of norepinephrine release from sympathetic nerve terminals, acting as an autoreceptor?
19. A 60-year-old man taking prazosin for benign prostatic hyperplasia develops sudden severe hypotension on standing after his first dose. The mechanism responsible is BEST described as:
20. Pharmacogenomics: A patient with CYP2D6 poor metaboliser status is prescribed metoprolol. The expected clinical consequence is:
21. Nebivolol differs from other beta-1 selective blockers by additionally releasing nitric oxide via stimulation of which receptor pathway?
22. A patient with pheochromocytoma crisis develops severe hypertension and tachycardia after a single dose of propranolol administered without prior alpha-blockade. The worsening hypertension is best explained by:
23. Which of the following muscarinic receptor subtypes is predominantly responsible for the pirenzepine-sensitive inhibition of gastric acid secretion?
24. CYP2D6 poor metabolizer status significantly affects the clinical outcome with which of the following beta-blockers due to accumulation of active parent drug?
25. A 35-year-old woman with angle-closure glaucoma is started on a cholinergic drug to lower intraocular pressure. Which receptor subtype mediates the contraction of the ciliary muscle leading to increased aqueous outflow through the trabecular meshwork?
26. A patient receiving neostigmine for reversal of neuromuscular blockade develops severe bradycardia and excessive salivation. The treating anaesthesiologist administers glycopyrrolate instead of atropine. Which property of glycopyrrolate best explains why it is preferred in this context?
27. Alpha-2 adrenoceptors on presynaptic noradrenergic nerve terminals serve as autoreceptors. Activation of these receptors by an agonist such as clonidine leads to which of the following primary intracellular consequences?
28. A 58-year-old man with benign prostatic hyperplasia and hypertension is being started on tamsulosin. Unlike prazosin, tamsulosin does not cause first-dose orthostatic hypotension to the same degree. Which best explains the pharmacological basis for this difference?
29. Phenoxybenzamine is used in preoperative management of phaeochromocytoma. Compared to phentolamine, which statement correctly characterises its mechanism of action?
30. A 40-year-old woman taking metoclopramide for gastroparesis develops acute torticollis and oculogyric crisis one hour after the dose. The emergency physician administers a drug that reverses these symptoms within minutes. Which drug was most likely administered?
31. A 58-year-old man with heart failure on carvedilol develops worsening hyperglycemia. The mechanism by which carvedilol impairs glucose homeostasis differs from that of selective beta-1 blockers because carvedilol additionally blocks:
32. Which pharmacogenomic variation is most clinically relevant when prescribing metoprolol in a patient who reports excessive bradycardia at standard doses?
33. The vasodilatory action of clonidine used in hypertensive emergency (IV) is opposite to its usual antihypertensive effect. This paradoxical pressor response is due to stimulation of:
34. Mirabegron, used for overactive bladder, differs mechanistically from antimuscarinics such as oxybutynin because it acts as a:
35. A patient with Horner syndrome from a carotid dissection is given a dilute cocaine eye drop test. Cocaine fails to dilate the affected pupil because it acts by:
36. A patient with refractory vasodilatory shock is unresponsive to norepinephrine. The intensivist adds vasopressin. Which receptor subtype mediates vasopressin-induced vasoconstriction in peripheral vascular smooth muscle?
37. A 45-year-old man with autonomic neuropathy undergoes pharmacogenomic testing that reveals he is an ultrarapid metabolizer of CYP2D6. He is prescribed metoprolol for hypertension. Which consequence is most likely?
38. Phenoxybenzamine is used in pre-operative management of phaeochromocytoma rather than a short-acting alpha-blocker because it:
39. A patient on clonidine for hypertension suddenly stops the drug. Which mechanism best explains the rebound hypertension observed?
40. Which statement best describes the pharmacodynamic basis for using low-dose dopamine as a 'renal-dose' agent, and why this practice is now questioned?
41. A patient with myasthenia gravis on pyridostigmine develops profuse secretions, miosis, and bradycardia after a dose increase. The mechanism responsible for the muscarinic side effects of pyridostigmine but NOT for its therapeutic benefit involves which receptor subtype?
42. A pharmacogenomics study reveals that poor metabolizers of CYP2D6 who receive a standard dose of metoprolol are most likely to experience which adverse effect due to elevated plasma drug levels?
43. During laparoscopic surgery, the surgeon requests a drug to reduce intraoperative bronchospasm triggered by tracheal intubation. The patient has benign prostatic hyperplasia and narrow-angle glaucoma. Which muscarinic antagonist is SAFEST in this setting?
44. Clonidine exerts its antihypertensive effect primarily by acting as an agonist at which receptor subtype, and what is the consequence of abrupt withdrawal?
45. A patient with pheochromocytoma is scheduled for surgery. Alpha-blockade is initiated with phenoxybenzamine. Why is a beta-blocker added ONLY AFTER adequate alpha-blockade is established?
46. A 58-year-old patient on prazosin develops orthostatic hypotension worst with the first dose. The mechanism underlying this 'first-dose phenomenon' is best explained by:
47. Bethanechol is preferred over methacholine for testing bladder detrusor function because:
48. A patient with pheochromocytoma crisis is given phentolamine. During infusion, the heart rate increases markedly. This tachycardia is primarily due to:
49. Clonidine withdrawal syndrome produces a hypertensive crisis because:
50. A patient with neurogenic bladder is treated with mirabegron. The mechanism of action of mirabegron differs from older agents used for overactive bladder in that it:
51. A 62-year-old man with Alzheimer's disease is started on donepezil. The drug inhibits acetylcholinesterase predominantly at which molecular site to prolong ACh action?
52. Prazosin causes a first-dose hypotension more pronounced than that of doxazosin at equivalent doses. The pharmacokinetic basis for this differential effect is best explained by:
53. A patient receiving clonidine for hypertension abruptly stops the drug and presents 24 hours later with severe hypertension, palpitations, and diaphoresis. The mechanism of rebound hypertension is primarily:
54. Which β-blocker is preferred in a patient with stable COPD requiring treatment for hypertension and angina, and why?
55. A pharmacogenomics study reveals that a patient carries the CYP2D6*4/*4 genotype (poor metabolizer). This patient is started on metoprolol. The expected pharmacodynamic consequence is:
56. A 58-year-old man with benign prostatic hyperplasia and overactive bladder is prescribed a muscarinic antagonist. Which agent has the highest selectivity for the M3 receptor in the bladder with minimal cognitive adverse effects due to poor CNS penetration?
57. Mirabegron, a beta-3 adrenergic agonist used for overactive bladder, exerts its therapeutic effect primarily by which mechanism?
58. A patient on timolol eye drops for glaucoma develops worsening of bronchospasm. The ophthalmologist switches to betaxolol. The rationale is that betaxolol is which of the following?
59. Which of the following best describes the pharmacogenomic basis for the variable response to debrisoquine and other drugs metabolized by the same hepatic enzyme?
60. A patient with pheochromocytoma is being prepared for surgery. Phenoxybenzamine is preferred over phentolamine for preoperative alpha-blockade. What is the key pharmacological reason?
61. A patient on a non-selective beta-blocker develops paradoxical hypertension after receiving epinephrine for an anaphylactic reaction. Which adrenoceptor subtype interaction best explains this phenomenon?
62. The desensitization of beta-adrenoceptors following prolonged agonist exposure is primarily mediated by which intracellular mechanism?
63. In a patient with pheochromocytoma undergoing preoperative preparation, which pharmacological principle justifies initiating an alpha-blocker BEFORE a beta-blocker?
64. Mirabegron, used for overactive bladder, acts through which mechanism distinct from traditional anticholinergic agents?
65. Ipratropium bromide, unlike atropine, does not cross the blood-brain barrier primarily because it:
66. A patient on prazosin develops tachycardia after the first dose. The mechanism responsible is:
67. Which mechanism best explains why neostigmine is preferred over physostigmine for reversing non-depolarizing neuromuscular blockade?
68. Carvedilol differs from metoprolol in heart failure management principally because carvedilol additionally blocks:
69. A patient with pheochromocytoma crisis is inadvertently given IV propranolol without prior alpha-blockade. The expected outcome is:
70. Methyldopa is used in hypertension in pregnancy. Its active antihypertensive metabolite and primary site of action are:
71. A patient with organophosphate poisoning is treated with atropine. The mechanism by which atropine reverses bradycardia in this setting specifically involves blockade of which receptor subtype at the sinoatrial node?
72. A 68-year-old man develops urinary hesitancy and blurred vision after starting a drug. His prescription includes tamsulosin for BPH and the newly added drug. Which pharmacological property best explains why the new drug causes these anticholinergic side effects while tamsulosin does not?
73. Clonidine withdrawal results in rebound hypertension because of which precise receptor-level mechanism?
74. A patient taking a non-selective beta-blocker develops paradoxical severe hypertension after receiving epinephrine for an anaphylactic reaction. Which mechanism best explains this paradox?
75. Which pharmacogenomic variation most significantly alters the clinical response to metoprolol, and what is the functional consequence of the 'poor metaboliser' phenotype?
76. A patient with myasthenia gravis crisis is inadvertently given excess neostigmine. Which of the following signs would most reliably distinguish cholinergic crisis from myasthenic crisis?
77. Which of the following correctly describes the mechanism by which prazosin causes first-dose syncope?
78. A 60-year-old man being treated with bethanechol for post-operative urinary retention suddenly develops severe abdominal cramping, sweating, and bradycardia. The best immediate treatment is:
79. Phenylephrine, when used as a nasal decongestant spray, acts predominantly on which receptor subtype to produce vasoconstriction?
80. A patient on long-term clonidine for hypertension abruptly discontinues the drug. Two days later, she presents with severe headache, palpitations, and BP 210/130 mmHg. This rebound hypertension is due to:
81. A 45-year-old patient exposed to organophosphate insecticide is brought to casualty with pinpoint pupils, excessive secretions, bradycardia, muscle fasciculations, and seizures. The correct sequence of antidote administration is:
82. Dobutamine is preferred over dopamine in acute decompensated heart failure without hypotension because:
83. A 62-year-old man with benign prostatic hyperplasia and overactive bladder is started on a muscarinic antagonist. The drug chosen has the highest selectivity for the M3 receptor in the bladder with minimal M2-mediated cardiac effects. Which drug best fits this description?
84. Ephedrine acts on adrenergic receptors primarily by which mechanism that distinguishes it from adrenaline?
85. A patient on a non-selective beta-blocker experiences a hypertensive crisis after receiving adrenaline. The mechanism is best explained by:
86. Which alpha-1 blocker is most selective for alpha-1A receptors in the prostate and bladder neck, making it preferred in BPH with minimal effect on blood pressure?
87. A 60-year-old man with Alzheimer's disease is prescribed rivastigmine. The drug inhibits acetylcholinesterase and butyrylcholinesterase. Which property best explains the PREFERENTIAL central action of rivastigmine compared to neostigmine?
88. Hemicholinium-3 (HC-3) blocks cholinergic transmission. What is its exact site and mechanism of action?
89. A patient on clonidine for hypertension abruptly stops the drug. The rebound hypertension that follows is primarily due to:
90. Which of the following beta-blockers undergoes extensive first-pass metabolism, has the shortest half-life, and is used as an IV agent to control perioperative supraventricular tachycardia?
91. A 45-year-old with pheochromocytoma is scheduled for surgery. Prior to giving propranolol for tachycardia, an alpha-blocker must be given first because propranolol alone would cause:
92. A 65-year-old man is started on tamsulosin for benign prostatic hyperplasia. Which receptor subtype does tamsulosin preferentially block to achieve its therapeutic effect with minimal cardiovascular side effects?
93. The mydriasis produced by tropicamide during a routine ophthalmic examination is primarily due to blockade of which receptor on the iris sphincter pupillae?
94. A patient presents with bradycardia, bronchospasm, miosis, urinary incontinence, and excessive lacrimation after agricultural work. Which enzyme's inhibition most directly explains the urinary incontinence in this cholinergic toxidrome?
95. Dobutamine is used in cardiogenic shock to increase cardiac output. Its predominant mechanism of benefit is activation of which receptor?
96. A 30-year-old woman with paroxysmal supraventricular tachycardia is given adenosine IV. The drug terminates the arrhythmia by which mechanism?
97. A researcher studies the effect of a drug that selectively blocks presynaptic α2-adrenoreceptors at noradrenergic terminals. Which of the following best describes the expected physiological consequence?
98. Which muscarinic receptor subtype mediates the pirenzepine-sensitive inhibition of gastric acid secretion, and what is its primary G-protein coupling?
99. A 45-year-old man receives phenoxybenzamine before adrenalectomy for pheochromocytoma. Unlike phentolamine, phenoxybenzamine is preferred because it:
100. Methacholine challenge test is used in bronchial hyperresponsiveness assessment. The mechanism by which methacholine induces bronchoconstriction is best described as:
101. Dobutamine is chosen over dopamine in cardiogenic shock without significant hypotension because dobutamine:
102. A patient with open-angle glaucoma is prescribed a drug that reduces intraocular pressure by increasing aqueous humor outflow through the trabecular meshwork AND directly decreasing aqueous production. Which receptor mechanism accounts for BOTH these actions simultaneously?
103. Prazosin is used in a patient with benign prostatic hyperplasia. Unlike doxazosin, prazosin requires more frequent dosing because it lacks which pharmacokinetic property?
104. A patient undergoing pheochromocytoma resection develops severe hypertension after tumor manipulation. The anesthesiologist administers phentolamine IV. What is the most important reason that a beta-blocker should NOT be administered first in this setting?
105. A 45-year-old woman on clonidine for hypertension abruptly stops the medication. She develops severe hypertension, tachycardia, and diaphoresis 18 hours later. The mechanism responsible is:
106. Neostigmine administered post-operatively to reverse neuromuscular blockade is always co-administered with atropine. The specific muscarinic effect that makes this co-administration MOST critical for patient safety is:
107. A patient with diabetes takes metoclopramide for gastroparesis. After 3 months of daily use, she develops involuntary repetitive jaw movements and tongue protrusion. The mechanism of this adverse effect is:
108. Dobutamine is used in acute decompensated heart failure. Unlike dopamine, dobutamine does NOT increase renal blood flow significantly because:
109. A patient with primary open-angle glaucoma is started on a miotic agent that acts by inhibiting acetylcholinesterase irreversibly. This drug also carries a risk of causing a paradoxical increase in intraocular pressure. Which of the following best describes this mechanism?
110. A 30-year-old woman undergoes elective surgery. During reversal of neuromuscular blockade, neostigmine is administered but she develops severe bradycardia requiring atropine. Which receptor subtype mediates the cardiac slowing produced by neostigmine in this scenario?
111. A pharmaceutical company develops a selective alpha-2A adrenoceptor agonist for treating ADHD. The drug reduces norepinephrine release from presynaptic terminals in the prefrontal cortex. Which drug among the following shares this predominant mechanism and is currently approved for ADHD?
112. A 55-year-old man with pheochromocytoma is prepared for surgery. Phenoxybenzamine is started 10-14 days preoperatively. The drug produces a non-competitive, irreversible alpha-adrenergic blockade. What is the clinical consequence of this irreversibility during surgical tumour manipulation?
113. A patient on clonidine for hypertension suddenly stops the drug. He presents with severe rebound hypertension, agitation, and sweating. The mechanism of this rebound is best explained by:
114. A pharmacologist studies a drug that activates presynaptic alpha-2 adrenoceptors at sympathetic nerve terminals in the heart. The expected net effect of this drug would be:
115. Which of the following best explains why indirect sympathomimetics like amphetamine lose efficacy with repeated dosing (tachyphylaxis)?
116. A patient with angle-closure glaucoma is prescribed a drug for urinary incontinence. Which muscarinic receptor subtype-selective drug would be SAFEST with least concern for raising intraocular pressure?
117. A research compound selectively blocks ganglionic nicotinic receptors (Nn subtype) but not neuromuscular nicotinic receptors (Nm subtype). The expected clinical effect would primarily be:
118. Phenoxybenzamine differs from phentolamine in its mechanism of alpha-adrenoceptor blockade primarily because phenoxybenzamine:
119. A patient receiving a beta-blocker (propranolol) for hypertension is given epinephrine for anaphylaxis. An unexpected dangerous effect in this scenario would be:
120. Which drug would be MOST appropriate for rapid reversal of the hypotension caused by a phentolamine overdose?
121. A patient on long-term treatment with a selective M3 muscarinic antagonist for overactive bladder develops blurred near vision. The most likely mechanism responsible for this ocular side effect is:
122. Prazosin differs from phenoxybenzamine in that prazosin:
123. A 60-year-old man taking a non-selective beta-blocker for hypertension is given a subcutaneous dose of adrenaline for anaphylaxis. Which of the following haemodynamic consequences is most likely?
124. Which statement best describes the mechanism by which neostigmine produces its therapeutic effect in myasthenia gravis?
125. A 25-year-old farmer presents with miosis, salivation, lacrimation, bradycardia, and muscle fasciculations after accidental pesticide exposure. Which antidote should be administered FIRST to reverse the immediate life-threatening features?
126. A patient with pheochromocytoma crisis is given phentolamine intravenously. Within minutes, the blood pressure drops sharply but is accompanied by tachycardia. Which receptor mechanism best explains the tachycardia seen after phentolamine administration?
127. Hemicholinium-3 produces a cholinergic blockade that resembles, but is mechanistically distinct from, botulinum toxin. What is the precise site of action of hemicholinium-3?
128. A 60-year-old man on clonidine for hypertension abruptly stops the drug. He presents with severe rebound hypertension and sweating. The mechanism of clonidine's antihypertensive action and the rebound involves which receptor?
129. Which of the following correctly pairs a sympathomimetic drug with its primary mechanism of action that is NOT direct receptor stimulation?
130. A clinical researcher tests a new drug that causes marked miosis, lacrimation, and salivation, but produces no skeletal muscle fasciculations. This pattern most likely indicates the drug is a selective:
131. A patient on a ganglionic blocker for hypertensive emergency is unable to urinate. Which receptor subtype, when blocked at the parasympathetic ganglion, is primarily responsible for this effect?
132. Prazosin administered to a patient with BPH causes postural hypotension. Which mechanism best explains the hypotension, distinct from its therapeutic effect on the bladder outlet?
133. A 60-year-old man is administered a drug that causes sweating, salivation, and miosis but NO bradycardia, and the effects are NOT reversed by atropine. The most likely mechanism is:
134. A patient with pheochromocytoma undergoing surgery develops a hypertensive crisis. The anesthesiologist administers phentolamine. The CORRECT statement about phentolamine's pharmacology is:
135. A patient is started on clonidine for hypertension. The drug is abruptly stopped after 4 weeks. Which life-threatening adverse effect is MOST likely to occur?
136. A pharmacologist studies a drug that activates M2 muscarinic receptors in the sinoatrial node. Which intracellular mechanism directly mediates the negative chronotropy produced by this drug?
137. A patient with open-angle glaucoma is started on a topical drug that reduces intraocular pressure by enhancing uveoscleral outflow AND constricting the pupil. Which drug is responsible?
138. Prazosin causes first-dose hypotension primarily because it selectively blocks which adrenoceptor subtype at post-synaptic vascular smooth muscle while sparing the presynaptic autoreceptor that limits noradrenaline release?
139. Which beta-blocker is preferred in a patient with COPD who requires treatment for angina because it has the highest cardioselectivity (beta-1 selectivity) among the following options?
140. A patient receives a drug that produces mydriasis without cycloplegia and is used to facilitate ophthalmic examination. Which receptor selectivity best explains this pharmacological profile?
141. Clonidine produces sedation and reduces blood pressure primarily by acting on which receptor subtype and through which second messenger pathway?
142. Which muscarinic receptor subtype predominantly mediates the relaxation of the detrusor muscle of the urinary bladder, making it the target of drugs used in overactive bladder?
143. A patient on a non-selective β-blocker (propranolol) develops bronchospasm. The bronchoconstriction is due to blockade of which receptor subtype and the resulting decrease in which intracellular messenger?
144. Prazosin differs from phenoxybenzamine in that prazosin is a:
145. Neostigmine reverses neuromuscular blockade by non-depolarizing agents. Its primary mechanism is:
146. A 60-year-old man presents with anhidrosis, urinary retention, dry mouth, and mydriasis after eating wild berries. This toxidrome is best treated with:
147. A patient with organophosphate poisoning is treated with atropine. Which muscarinic receptor subtype mediates the cardiac effects that atropine reverses in this setting?
148. A 65-year-old man on prazosin for BPH develops postural hypotension. The mechanism is best explained by blockade of which receptor subtype at vascular smooth muscle?
149. Which of the following correctly describes the mechanism by which indirect-acting sympathomimetics like amphetamine increase norepinephrine at the synapse?
150. A patient receives a ganglionic blocker. Which of the following effects would NOT be expected?
151. Clonidine lowers blood pressure primarily by acting on which receptor population?
152. A patient with open-angle glaucoma requires miotic therapy. The drug that acts by inhibiting acetylcholinesterase irreversibly and is used as a long-acting miotic in this setting is:
153. Prazosin differs from phentolamine in that prazosin:
154. A patient on clonidine for hypertension suddenly stops the drug. The mechanism of the ensuing rebound hypertension is:
155. Neostigmine is preferred over physostigmine for reversal of non-depolarizing neuromuscular blockade because neostigmine:
156. Which of the following sympathomimetics is used in the management of neurogenic orthostatic hypotension because it releases noradrenaline from sympathetic nerve terminals?
157. A 55-year-old man with benign prostatic hyperplasia and hypertension is started on a drug that selectively blocks alpha-1A adrenoceptors in the bladder neck and prostate smooth muscle with minimal effect on vascular tone. Which drug best fits this description?
158. During a surgical procedure, a patient inadvertently receives an overdose of a non-depolarising neuromuscular blocker. Which combination is the most appropriate reversal agent?
159. A patient on clonidine for hypertension abruptly stops the drug and develops severe rebound hypertension, sweating, and palpitations within 18 hours. What is the primary mechanism underlying this rebound phenomenon?
160. A 28-year-old woman with myasthenia gravis requires a muscle relaxant for a brief surgical procedure. Which agent is the SAFEST choice given her condition?
161. A young man presents with profuse sweating, miosis, bradycardia, excessive salivation, and muscle fasciculations after working in an agricultural field. Which drug should be administered FIRST?
162. A 58-year-old man with paroxysmal supraventricular tachycardia requires urgent pharmacological cardioversion. The physician administers a drug that acts by stimulating cardiac M2 receptors, slowing AV nodal conduction. This drug most likely also causes which of the following peripheral effects?
163. Phenylephrine administered intravenously to a normotensive subject causes a rise in blood pressure followed by bradycardia. The bradycardia is best explained by:
164. A patient with pheochromocytoma is being prepared for surgical removal of the tumor. Which of the following drugs would be MOST appropriate to control the hypertensive crisis before and during surgery?
165. Dobutamine is preferred over dopamine in a patient with acute heart failure and low cardiac output primarily because dobutamine:
166. Isoprenaline (isoproterenol) is used as a temporary bridge in complete heart block pending pacemaker insertion. Which of the following adverse effects is most likely with this drug in this setting?
167. Ephedrine differs from adrenaline (epinephrine) in all of the following respects EXCEPT:
168. Amphetamine produces its sympathomimetic effects primarily by:
169. A patient on a monoamine oxidase inhibitor (MAOI) for depression ingests tyramine-rich aged cheese and develops a hypertensive crisis. The mechanism is best described as:
170. Prazosin, used in the treatment of benign prostatic hyperplasia, relieves urinary outflow obstruction through which mechanism?
171. A 70-year-old man with BPH is started on tamsulosin. Compared to prazosin, tamsulosin is preferred because it:
172. Propranolol is contraindicated in a patient with vasospastic (Prinzmetal) angina because:
173. Esmolol is the preferred beta-blocker for controlling heart rate during intraoperative tachycardia because:
174. Labetalol is unique among beta-blockers used for hypertensive emergencies because it:
175. Nebivolol, a third-generation beta-blocker, lowers blood pressure through an additional mechanism not shared by propranolol. This additional mechanism is:
176. Timolol eye drops are used in open-angle glaucoma. The mechanism of IOP reduction is:
177. Carvedilol is preferred over metoprolol in patients with heart failure with reduced ejection fraction (HFrEF) in part because carvedilol additionally:
178. A patient with narrow-angle glaucoma is mistakenly prescribed pilocarpine. Which of the following best describes the expected effect on the pupil and intraocular pressure?
179. Bethanechol is preferred over pilocarpine for treating postoperative urinary retention because:
180. A patient with myasthenia gravis who is also asthmatic requires an anticholinesterase. Neostigmine is preferred over physostigmine in this context because:
181. Edrophonium is used for the Tensilon test in suspected myasthenia gravis. Compared to neostigmine, edrophonium has all of the following characteristics EXCEPT:
182. Donepezil is used in Alzheimer's disease. Its primary mechanism of action is:
183. Atropine is used to reverse bradycardia during general anesthesia. Which of the following effects would atropine NOT be expected to produce?
184. Glycopyrrolate is preferred over atropine for premedication in anesthesia to reduce secretions because:
185. A patient with COPD is prescribed an inhaled anticholinergic bronchodilator. Ipratropium is preferred over systemic atropine because ipratropium:
186. A 55-year-old woman with overactive bladder (OAB) is prescribed oxybutynin. The most common reason patients discontinue oxybutynin therapy is:
187. Hyoscine (scopolamine) is used for motion sickness prophylaxis applied as a transdermal patch. The antiemetic effect is mediated by:
188. Hexamethonium, a ganglion blocker, produces which of the following by its action at parasympathetic ganglia supplying the gut?
189. A patient undergoing endotracheal intubation is given succinylcholine. Shortly after administration, the anesthesiologist notes fasciculations followed by complete paralysis. A patient with pseudocholinesterase deficiency would be expected to:
190. Rocuronium-induced neuromuscular blockade can be rapidly and completely reversed by sugammadex through which mechanism?
191. Entacapone, a COMT inhibitor used in Parkinson's disease as an adjunct to levodopa, exerts its therapeutic benefit by:
192. A patient on long-term prazosin therapy for benign prostatic hyperplasia develops symptomatic hypotension after taking his first dose of tamsulosin prescribed by a new physician. The mechanism underlying this exaggerated hypotensive response is:
193. Neostigmine reverses non-depolarizing neuromuscular blockade more reliably when a TOF (train-of-four) count of at least 2 twitches is present. The principal reason neostigmine CANNOT reverse a dense succinylcholine block is:
194. A 65-year-old with heart failure on carvedilol develops worsening bronchospasm. Switching to metoprolol succinate reduces bronchospasm. The property of metoprolol that accounts for this differential effect is:
195. A patient receives a high intravenous dose of epinephrine. Which hemodynamic sequence best describes the complete cardiovascular response?
196. A patient with pheochromocytoma is prepared for surgery. Why is it essential to establish adequate alpha-adrenergic blockade with phenoxybenzamine BEFORE adding a beta-blocker?
197. A patient with pheochromocytoma requires surgical resection. During anesthetic induction, the patient develops hypertensive crisis. The resident proposes immediate IV labetalol. The attending surgeon objects. What is the pharmacological basis for this objection?
198. A pharmacology researcher studies the effects of a drug that selectively binds to presynaptic alpha-2 adrenoceptors on sympathetic nerve terminals. When given to a patient with hypertension, which hemodynamic profile is expected?
199. Organophosphate poisoning causes excessive acetylcholine accumulation at synapses. A toxicology resident notes that pralidoxime (2-PAM) must be given within a specific time window. What is the sub-molecular basis for this time limitation?
200. Phenylephrine is used as a nasal decongestant. When applied topically, which receptor subtype does it primarily activate and what is the molecular consequence in vascular smooth muscle cells?
201. A patient with overflow urinary incontinence due to an acontractile detrusor after spinal cord injury is started on bethanechol. The treating physician chooses bethanechol over methacholine specifically because of one pharmacokinetic property. What is this property?
202. A patient with organophosphate poisoning is treated with atropine plus pralidoxime. The primary biochemical reason pralidoxime must be given within 24–48 hours of poisoning is:
203. Clonidine produces antihypertensive action mainly by stimulating α2A-adrenoceptors in the rostral ventrolateral medulla (RVLM). When clonidine is abruptly withdrawn, which receptor-level mechanism underlies the rebound hypertension?
204. A 60-year-old patient with pheochromocytoma is undergoing preoperative preparation. Which sequence of adrenergic blockade is mandatory and why?
205. Nebivolol differs from other β1-selective blockers in its additional vasodilatory mechanism. This is due to:
206. A 35-year-old man with known myasthenia gravis is prescribed bethanechol for neurogenic bladder. What is the mechanistic basis by which bethanechol is preferred over other cholinomimetics in this setting?
207. A patient with pheochromocytoma is prepared for surgery. Alpha-blockade is initiated with phenoxybenzamine. Which of the following best describes its pharmacological mechanism?
208. Prazosin causes a characteristic 'first-dose hypotension' unlike tamsulosin. The pharmacological basis for this difference is:
209. A researcher is studying the effects of clonidine at presynaptic alpha-2 receptors on a sympathetic nerve terminal. Activation of these receptors will:
210. Which of the following correctly distinguishes the pharmacokinetics of atropine from glycopyrrolate?
211. A patient on bethanechol for neurogenic bladder develops excessive muscarinic effects. Which receptor subtypes does bethanechol predominantly stimulate?
212. A patient with organophosphate poisoning is treated with atropine and pralidoxime. Which statement best explains why pralidoxime must be given within 24–48 hours of exposure?
213. A 60-year-old man with Parkinson's disease is started on a drug that selectively blocks muscarinic M1 receptors in the striatum with minimal peripheral effects. Which drug best fits this profile?
214. Phenoxybenzamine differs from phentolamine in that it:
215. A drug produces bradycardia that is blocked by atropine, vasodilation that persists after atropine, and stimulation of nicotinic ganglionic receptors. Which receptor profile matches this drug?
216. Labetalol is used in hypertensive emergencies in pregnancy primarily because it:
217. A 72-year-old man with BPH is prescribed tamsulosin for urinary outflow obstruction. Tamsulosin's selectivity for alpha-1A receptors (over alpha-1B) explains why it causes less orthostatic hypotension. Where are alpha-1A receptors predominantly located?
218. A patient presents with classic features of organophosphate poisoning: miosis, bradycardia, bronchospasm, increased secretions and muscle fasciculations. The drug that treats both nicotinic (muscle) and muscarinic effects in severe OP poisoning is:
219. Dobutamine is used in cardiogenic shock for its positive inotropic effect. Its mechanism differs from dopamine. Dobutamine's primary haemodynamic action results from activation of which receptor?
220. Guanethidine is an adrenergic neuron blocker that was formerly used for hypertension. It enters noradrenergic nerve terminals via which mechanism?
221. A patient with severe organophosphate poisoning presents with SLUDGE features and is treated with atropine and pralidoxime (2-PAM). Pralidoxime is most effective when given within:
222. A 45-year-old with Raynaud's phenomenon is given a drug that selectively blocks alpha-1A and alpha-1B adrenoceptors without blocking alpha-2 receptors. Which advantage does this selectivity confer compared with a non-selective alpha-blocker?
223. Tyramine in aged cheese can cause a hypertensive crisis in a patient on a non-selective MAO inhibitor (MAOI). The mechanism is: