A 36-year-old man recovered from an acute cholinergic crisis after organophosphate ingestion, and needed less atropine by day 2. On day 3 he develops weakness of neck flexion, proximal limb muscles and some cranial nerves, with falling tidal volume, but no fasciculations or excess secretions. What is the most likely diagnosis?

OP-induced delayed polyneuropathy

A 70-year-old man taking tamsulosin for benign prostatic hyperplasia is listed for cataract surgery at a district eye camp. What should the ophthalmologist anticipate during the operation?

Intraoperative floppy iris syndrome

Severe intraoperative bradycardia

Autonomic drugs and neuromuscular blockers

23 NEET-PG practice questions on Autonomic drugs and neuromuscular blockers, part of Pharmacology. The first 23 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Easy
A 35-year-old farmer is brought to casualty an hour after drinking a pesticide. He has pinpoint pupils, profuse sweating and salivation, wheeze with copious bronchial secretions, and pulse 48/min. Which drug is given first and titrated until the chest is clear?
1. APralidoxime
2. BAtropine
3. CAdrenaline
4. DPhysostigmine
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Answer: B · Atropine
This is the muscarinic crisis of organophosphate poisoning, caused by acetylcholine build-up after acetylcholinesterase is inhibited. Atropine blocks muscarinic receptors and is given in doubling bolus doses until the chest is clear, heart rate and BP are adequate, and the skin is dry. It does not reverse nicotinic effects such as muscle weakness. Secretions in the airway are the main cause of early death, so atropinisation comes first.
- A: Pralidoxime reactivates the enzyme but acts slowly and does not dry secretions first.
- C: Adrenaline does not block muscarinic receptors or clear secretions.
- D: Physostigmine inhibits cholinesterase and would worsen the crisis.
Question 2 · Easy
A 67-year-old retired teacher with mild asthma, well controlled on an inhaled steroid, is given eye drops for raised intraocular pressure at an eye camp. Within ten days she needs her reliever inhaler several times a day and wakes at night wheezing. Which eye drop is the most likely culprit?
1. ADorzolamide
2. BLatanoprost
3. CTimolol
4. DBrimonidine
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Answer: C · Timolol
Timolol is a non-selective beta blocker, and eye drops drain through the nasolacrimal duct into the nasal mucosa, from where they are absorbed into the circulation without first-pass metabolism. Blocking beta-2 receptors in bronchial smooth muscle can trigger severe bronchospasm in asthmatics, and blocking cardiac beta-1 receptors can cause bradycardia. Topical beta blockers are avoided in asthma, and pressing on the inner canthus after instilling drops reduces systemic absorption. Prostaglandin analogues such as latanoprost are a suitable alternative.
- A: Dorzolamide, a carbonic anhydrase inhibitor, causes stinging and bitter taste, not bronchospasm.
- B: Latanoprost, a prostaglandin analogue, causes iris darkening and lash growth, not bronchospasm.
- D: Brimonidine, an alpha-2 agonist, causes allergy, dry mouth and drowsiness, not bronchospasm.
Question 3 · Medium
A 36-year-old man recovered from an acute cholinergic crisis after organophosphate ingestion, and needed less atropine by day 2. On day 3 he develops weakness of neck flexion, proximal limb muscles and some cranial nerves, with falling tidal volume, but no fasciculations or excess secretions. What is the most likely diagnosis?
1. AAtropine toxicity
2. BRecurrent cholinergic crisis
3. CIntermediate syndrome
4. DOP-induced delayed polyneuropathy
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Answer: C · Intermediate syndrome
Intermediate syndrome appears about 24 to 96 hours after organophosphate poisoning, after the cholinergic crisis has settled. It is weakness of neck flexors, proximal limb muscles, cranial nerve muscles and respiratory muscles, attributed to sustained nicotinic receptor dysfunction at the neuromuscular junction. It responds poorly to atropine, and the key danger is respiratory failure, so breathing must be monitored and ventilation given when needed. It usually resolves in one to three weeks.
- A: Atropine toxicity causes delirium, dry skin and tachycardia, not proximal weakness.
- B: Recurrent cholinergic crisis brings back secretions, miosis and fasciculations.
- D: Delayed polyneuropathy starts after one to three weeks with distal weakness.
Question 4 · Easy
A 7-year-old boy is wheeled into theatre for adenotonsillectomy. The anaesthetist wants an antimuscarinic to dry secretions without causing central effects such as restlessness or delirium. Which drug is best suited?
1. AAtropine
2. BGlycopyrrolate
3. CHyoscine hydrobromide
4. DPhysostigmine
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Answer: B · Glycopyrrolate
Glycopyrrolate is a quaternary ammonium antimuscarinic; it is charged, so it hardly crosses the blood-brain barrier and has few central effects. It reduces salivary and airway secretions and prevents vagal bradycardia during anaesthesia. Atropine and hyoscine are tertiary amines that enter the brain; hyoscine is the most sedating and can cause delirium, especially in children and the elderly. Glycopyrrolate is also given with neostigmine during reversal of neuromuscular block.
- A: Atropine is a tertiary amine and can cause central excitation.
- C: Hyoscine crosses the blood-brain barrier and causes sedation and confusion.
- D: Physostigmine is a cholinesterase inhibitor and would increase secretions.
Question 5 · Medium
A 70-year-old man taking tamsulosin for benign prostatic hyperplasia is listed for cataract surgery at a district eye camp. What should the ophthalmologist anticipate during the operation?
1. ASevere intraoperative bradycardia
2. BMalignant hyperthermia
3. CAcute angle-closure glaucoma
4. DIntraoperative floppy iris syndrome
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Answer: D · Intraoperative floppy iris syndrome
Tamsulosin blocks alpha-1A receptors, including those in the iris dilator muscle. During cataract surgery the iris may billow, prolapse through the incisions and constrict progressively, known as intraoperative floppy iris syndrome. The surgeon should be told beforehand so that pupil-expanding devices or intracameral drugs can be used; stopping tamsulosin shortly before surgery may not prevent it. Postural hypotension is its other common adverse effect.
- A: Tamsulosin does not cause significant bradycardia.
- B: Malignant hyperthermia is triggered by volatile anaesthetics and succinylcholine.
- C: Alpha blockers do not cause angle closure; anticholinergics and adrenergic mydriatics can.
Question 6 · Medium
A 34-year-old woman has episodic headache, sweating and palpitations, BP 190/110 mmHg, and raised plasma free metanephrines. CT shows a 4-cm left adrenal mass, and surgery is planned. How should her BP be controlled before the operation?
1. AThiazide diuretic alone
2. BAlpha blockade first, then a beta blocker
3. CBeta blocker alone
4. DBeta blocker first, then alpha blockade
Answer and explanation in LearnFree account
Question 7 · Medium
A 78-year-old woman with urge incontinence was started on oxybutynin three weeks ago. Her daughter reports new forgetfulness and confusion, and she is constipated. Which drug relaxes the detrusor without antimuscarinic effects?
1. AMirabegron
2. BBethanechol
3. CSolifenacin
4. DTolterodine
Answer and explanation in LearnFree account
Question 8 · Easy
A 28-year-old man stung by bees at a mango farm develops generalised urticaria, stridor and a BP of 76/40 mmHg within minutes. What is the first drug to give, and by which route?
1. AAdrenaline 1:1000 as an intravenous bolus
2. BChlorpheniramine intramuscularly
3. CAdrenaline 1:1000 intramuscularly in the thigh
4. DHydrocortisone intravenously
Answer and explanation in LearnFree account
Question 9 · Medium
A 42-year-old farmer from Vidarbha is admitted after spraying an organophosphate insecticide without protection. He is atropinised, but muscle fasciculations and weakness persist. Pralidoxime is added. Why must the oxime be given as early as possible?
1. AIt blocks muscarinic receptors only early on
2. BIt is metabolised rapidly by the liver
3. CPhosphorylated enzyme ages and cannot be reactivated
4. DIt must reach the brain before atropine
Answer and explanation in LearnFree account
Question 10 · Easy
A 54-year-old man with an acute inferior wall MI has a pulse of 38/min, BP 80/50 mmHg and cold, clammy skin. The ECG shows sinus bradycardia. Which drug is given first?
1. AAtropine
2. BNeostigmine
3. CAdrenaline
4. DIsoprenaline
Answer and explanation in LearnFree account
Question 11 · Hard
A 62-year-old man in the CCU receives an infusion of a catecholamine. Readings before and after: systolic BP 90 to 140 mmHg, diastolic BP 50 to 88 mmHg, heart rate 92 to 74/min. Which drug was most likely infused?
1. ALow-dose adrenaline
2. BIsoprenaline
3. CDobutamine
4. DNoradrenaline
Answer and explanation in LearnFree account
Question 12 · Medium
A 48-year-old man with type 1 diabetes on insulin is started on propranolol for migraine prophylaxis. Which warning sign of hypoglycaemia is least affected by the beta blockade?
1. AFine tremor of the hands
2. BSweating
3. CRapid pulse
4. DPalpitations
Answer and explanation in LearnFree account
Question 13 · Hard
A 31-year-old man with acute schizophrenia is given a large dose of intramuscular chlorpromazine and becomes hypotensive, BP 72/40 mmHg. The intern plans to give adrenaline. Why could this worsen the hypotension?
1. AChlorpromazine converts adrenaline to isoprenaline
2. BAdrenaline is metabolised faster in the presence of chlorpromazine
3. CAdrenaline releases histamine from mast cells
4. DAlpha blockade leaves its beta-2 vasodilatation unopposed
Answer and explanation in LearnFree account
Question 14 · Medium
A 30-year-old woman with myasthenia gravis on pyridostigmine has been taking extra tablets for increasing weakness. She now has worsening weakness with profuse salivation, sweating, abdominal cramps, diarrhoea, small pupils and fasciculations. What is the most appropriate step?
1. AStart high-dose oral prednisolone alone
2. BDouble the dose of pyridostigmine
3. CGive intravenous neostigmine
4. DStop pyridostigmine and support breathing
Answer and explanation in LearnFree account
Question 15 · Hard
A 32-year-old man with 40% flame burns 12 days ago is taken for skin grafting. Serum potassium is 4.6 mmol/L. The anaesthetist plans rapid sequence induction because he has eaten. Which neuromuscular blocker is most appropriate?
1. ARocuronium
2. BAtracurium
3. CSuccinylcholine
4. DPancuronium
Answer and explanation in LearnFree account
Question 16 · Hard
A 40-year-old farmer is admitted after drinking chlorpyrifos. Consider these statements on his care: 1. Atropine is titrated to a clear chest, HR above 80/min, systolic BP above 80 mmHg and dry axillae 2. Atropine is titrated until the pupils are no longer constricted 3. An oxime is aimed at the nicotinic weakness atropine cannot reverse 4. Succinylcholine is the preferred relaxant if he needs intubation. Which statements are correct?
1. A1 only
2. B3 only
3. C1 and 3 only
4. D1, 3 and 4 only
Answer and explanation in LearnFree account
Question 17 · Medium
A 26-year-old woman is brought in after taking 30 tablets of propranolol 40 mg. She has HR 36/min and BP 70/40 mmHg that do not respond to atropine and IV fluids. Which drug raises cardiac output through a pathway that bypasses beta receptors?
1. AGlucagon
2. BDobutamine
3. CIsoprenaline
4. DPhysostigmine
Answer and explanation in LearnFree account
Question 18 · Medium
A 30-year-old man for emergency appendicectomy is intubated after succinylcholine. Which statements are true of the phase I (depolarising) block it produces? 1. Muscle fasciculations precede paralysis 2. No fade on train-of-four stimulation 3. Neostigmine prolongs rather than reverses it 4. Post-tetanic potentiation is marked
1. A1, 2 and 4 only
2. B1, 2 and 3 only
3. C3 only
4. D1 and 2 only
Answer and explanation in LearnFree account
Question 19 · Medium
A 25-year-old man receives succinylcholine for a 5-minute procedure. He remains apnoeic and needs ventilation for nearly two hours. His sister had a similar episode after an operation. Which test will best characterise his condition?
1. ASerum creatine kinase
2. BDibucaine number
3. CHalothane-caffeine contracture test
4. DAcetylcholine receptor antibody
Answer and explanation in LearnFree account
Question 20 · Medium
A 35-year-old woman undergoing laparoscopic cholecystectomy received rocuronium. At the end of the operation she still has a deep block (no response to train-of-four). Which drug reverses this block by binding the relaxant molecule directly?
1. ANeostigmine
2. BDantrolene
3. CSugammadex
4. DEdrophonium
Answer and explanation in LearnFree account
Question 21 · Hard
A 50-year-old woman received vecuronium for a 3-hour laparotomy. At the end, train-of-four stimulation gives four twitches with a fourth-to-first ratio of 0.5; she is breathing shallowly. What is the most appropriate next step before extubation?
1. AImmediate extubation
2. BNeostigmine with glycopyrrolate
3. CIntravenous dantrolene
4. DNeostigmine alone
Answer and explanation in LearnFree account
Question 22 · Medium
A 22-year-old man is brought to casualty after eating seeds from a roadside plant. He is agitated and hallucinating, with hot, dry, flushed skin, dilated unreactive pupils, pulse 140/min, absent bowel sounds and a distended bladder. Which antidote can reverse both his central and peripheral features?
1. APyridostigmine
2. BPralidoxime
3. CPhysostigmine
4. DNeostigmine
Answer and explanation in LearnFree account
Question 23 · Medium
A 59-year-old man with pneumonia in the ICU has BP 78/42 mmHg (MAP about 54 mmHg) after 30 mL/kg of IV crystalloid, warm peripheries and lactate 4.2 mmol/L. Which vasoactive drug is first-line?
1. ADobutamine
2. BDopamine
3. CNoradrenaline
4. DIsoprenaline
Answer and explanation in LearnFree account

Autonomic drugs and neuromuscular blockers

A 35-year-old farmer is brought to casualty an hour after drinking a pesticide. He has pinpoint pupils, profuse sweating and salivation, wheeze with copious bronchial secretions, and pulse 48/min. Which drug is given first and titrated until the chest is clear?

A 67-year-old retired teacher with mild asthma, well controlled on an inhaled steroid, is given eye drops for raised intraocular pressure at an eye camp. Within ten days she needs her reliever inhaler several times a day and wakes at night wheezing. Which eye drop is the most likely culprit?

A 7-year-old boy is wheeled into theatre for adenotonsillectomy. The anaesthetist wants an antimuscarinic to dry secretions without causing central effects such as restlessness or delirium. Which drug is best suited?

A 70-year-old man taking tamsulosin for benign prostatic hyperplasia is listed for cataract surgery at a district eye camp. What should the ophthalmologist anticipate during the operation?

A 34-year-old woman has episodic headache, sweating and palpitations, BP 190/110 mmHg, and raised plasma free metanephrines. CT shows a 4-cm left adrenal mass, and surgery is planned. How should her BP be controlled before the operation?

A 78-year-old woman with urge incontinence was started on oxybutynin three weeks ago. Her daughter reports new forgetfulness and confusion, and she is constipated. Which drug relaxes the detrusor without antimuscarinic effects?

A 28-year-old man stung by bees at a mango farm develops generalised urticaria, stridor and a BP of 76/40 mmHg within minutes. What is the first drug to give, and by which route?

A 42-year-old farmer from Vidarbha is admitted after spraying an organophosphate insecticide without protection. He is atropinised, but muscle fasciculations and weakness persist. Pralidoxime is added. Why must the oxime be given as early as possible?

A 54-year-old man with an acute inferior wall MI has a pulse of 38/min, BP 80/50 mmHg and cold, clammy skin. The ECG shows sinus bradycardia. Which drug is given first?

A 62-year-old man in the CCU receives an infusion of a catecholamine. Readings before and after: systolic BP 90 to 140 mmHg, diastolic BP 50 to 88 mmHg, heart rate 92 to 74/min. Which drug was most likely infused?

A 48-year-old man with type 1 diabetes on insulin is started on propranolol for migraine prophylaxis. Which warning sign of hypoglycaemia is least affected by the beta blockade?

A 31-year-old man with acute schizophrenia is given a large dose of intramuscular chlorpromazine and becomes hypotensive, BP 72/40 mmHg. The intern plans to give adrenaline. Why could this worsen the hypotension?

A 30-year-old woman with myasthenia gravis on pyridostigmine has been taking extra tablets for increasing weakness. She now has worsening weakness with profuse salivation, sweating, abdominal cramps, diarrhoea, small pupils and fasciculations. What is the most appropriate step?

A 32-year-old man with 40% flame burns 12 days ago is taken for skin grafting. Serum potassium is 4.6 mmol/L. The anaesthetist plans rapid sequence induction because he has eaten. Which neuromuscular blocker is most appropriate?

A 26-year-old woman is brought in after taking 30 tablets of propranolol 40 mg. She has HR 36/min and BP 70/40 mmHg that do not respond to atropine and IV fluids. Which drug raises cardiac output through a pathway that bypasses beta receptors?

A 25-year-old man receives succinylcholine for a 5-minute procedure. He remains apnoeic and needs ventilation for nearly two hours. His sister had a similar episode after an operation. Which test will best characterise his condition?

A 35-year-old woman undergoing laparoscopic cholecystectomy received rocuronium. At the end of the operation she still has a deep block (no response to train-of-four). Which drug reverses this block by binding the relaxant molecule directly?

A 50-year-old woman received vecuronium for a 3-hour laparotomy. At the end, train-of-four stimulation gives four twitches with a fourth-to-first ratio of 0.5; she is breathing shallowly. What is the most appropriate next step before extubation?

A 59-year-old man with pneumonia in the ICU has BP 78/42 mmHg (MAP about 54 mmHg) after 30 mL/kg of IV crystalloid, warm peripheries and lactate 4.2 mmol/L. Which vasoactive drug is first-line?