Toxicology: poisons and their management

27 NEET-PG practice questions on Toxicology: poisons and their management, part of Forensic Medicine. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Easy

   A 35-year-old farmer from Guntur is brought to casualty after drinking an insecticide. He has pinpoint pupils, profuse salivation, bronchorrhoea, a pulse of 48/min and muscle twitching. Atropine is started. What is the end point of atropinisation?

   1. AHeart rate above 140/min
   2. BFully dilated, non-reacting pupils
   3. CReturn of muscle power
   4. DClear chest with dry secretions

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   Answer: D · Clear chest with dry secretions

   Organophosphates inhibit acetylcholinesterase, causing muscarinic and nicotinic excess. Atropine blocks only muscarinic receptors and is titrated, with doubling doses, until the chest is clear on auscultation and secretions are dry, with heart rate above 80/min and systolic BP above 80 mmHg. Pupil size is a poor guide, and atropine does not reverse nicotinic effects such as muscle weakness. Over-atropinisation causes delirium, hyperthermia and tachycardia, which must be avoided.

   • A: Marked tachycardia indicates atropine toxicity, not the target.
   • B: Pupil dilation is a late, unreliable sign and is not the target.
   • C: Atropine does not act on nicotinic receptors, so muscle power does not guide the dose.

2. Question 2 · Medium

   A car driver is stopped by the traffic police in Pune at night and taken for a blood test, which shows an alcohol concentration of 45 mg per 100 mL of blood. He has no other drug in his blood and walks steadily. How does this level stand under the Motor Vehicles Act?

   1. AIt is below the legal limit of 80 mg/100 mL
   2. BOnly a clinical exam can decide the offence
   3. CIt exceeds the legal limit of 30 mg/100 mL
   4. DDriving with alcohol is legal if he walks steadily

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   Answer: C · It exceeds the legal limit of 30 mg/100 mL

   Under the Motor Vehicles Act, driving with more than 30 mg of alcohol per 100 mL of blood, as detected by a breath analyser or a blood test, is an offence, whether or not the driver looks drunk. Lower levels of alcohol already impair reaction time and judgement before obvious signs such as an unsteady gait appear. The figure of 80 mg/100 mL is the limit used in some other countries, not in India. The doctor collects the blood with a non-alcoholic skin antiseptic and adds sodium fluoride.

   • A: 80 mg/100 mL is the limit in some other countries, not India.
   • B: The legal offence is defined by the measured level, not by clinical signs.
   • D: A steady gait does not make driving above the limit legal.

3. Question 3 · Medium

   A 38-year-old farmer from Nashik is receiving polyvalent anti-snake venom infusion for a Russell's viper bite. Fifteen minutes into it he develops generalised urticaria, wheeze and a BP of 80/50 mmHg. What is the next best step?

   1. AStop ASV for good and give neostigmine
   2. BContinue ASV and give oral cetirizine
   3. CStop ASV and give IM adrenaline
   4. DSlow ASV and give IV hydrocortisone

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   Answer: C · Stop ASV and give IM adrenaline

   Urticaria, bronchospasm and hypotension during ASV are anaphylaxis, the most important early reaction to this equine antiserum. The infusion is stopped and intramuscular adrenaline (1 in 1,000) is given at once, with an antihistamine, hydrocortisone and IV fluids as adjuncts. Once he is stable, ASV is restarted slowly under close watch, because the venom still needs to be neutralised. Hydrocortisone acts too slowly to treat the reaction on its own.

   • A: ASV is still needed, and neostigmine has no role in anaphylaxis.
   • B: Continuing ASV with an oral drug risks fatal anaphylaxis.
   • D: Hydrocortisone is slow and is only an adjunct to adrenaline.

4. Question 4 · Easy

   A 10-year-old boy sleeping on the floor of his hut in a village in Bihar during the monsoon is brought to the PHC at dawn with drooping eyelids, slurred speech and difficulty swallowing. There are two faint marks on his hand with no swelling, pain or blistering, and the 20-minute whole blood clotting test is normal. Which snake most likely bit him?

   1. ARussell's viper
   2. BSaw-scaled viper
   3. CSpectacled cobra
   4. DCommon krait

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   Answer: D · Common krait

   A bite at night on someone sleeping on the floor, with almost no local signs, followed by ptosis and bulbar weakness and a normal clotting test, is typical of the common krait. Krait venom is mainly neurotoxic and causes little local tissue damage, so the bite is often painless and missed; abdominal pain is also common. Cobra bites are also neurotoxic but usually cause painful local swelling and necrosis. Polyvalent ASV is given, and breathing is watched closely because respiratory paralysis can come on quickly.

   • A: Russell's viper causes painful swelling and a non-clotting blood test.
   • B: Saw-scaled viper causes local swelling and coagulopathy, not paralysis.
   • C: Cobra bites usually cause painful local swelling and necrosis.

5. Question 5 · Hard

   The body of a 35-year-old man is recovered from a canal in Haryana four days after he went missing in summer; it is bloated and decomposed. Toxicology reports a femoral blood alcohol of 80 mg/100 mL, but vitreous humour alcohol is nil. His family insists he never drank. How should the blood result be interpreted?

   1. AVitreous alcohol is lost faster than blood alcohol
   2. BHe was drunk at the time he died
   3. CHe drank shortly before death, before absorption
   4. DAlcohol likely formed after death by microbes

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   Answer: D · Alcohol likely formed after death by microbes

   In a decomposed body, bacteria and yeasts can produce ethanol from glucose and other substrates after death, so a raised blood alcohol may be a post-mortem artefact. Vitreous humour is relatively sterile and protected, and in a person who drank before death the vitreous alcohol would be close to, or a little above, the blood level. A blood alcohol of 80 mg/100 mL with no vitreous alcohol therefore points to post-mortem formation. Urine and vitreous are collected with blood in every suspected alcohol death for this reason.

   • A: Vitreous humour retains alcohol well and resists putrefaction.
   • B: A true ante-mortem level would also appear in the vitreous.
   • C: Alcohol drunk shortly before death would still reach the vitreous and urine to some extent.

6. Question 6 · Hard

   A medical officer in Odisha is preparing a talk on snake bite for PHC staff and reviews four statements: 1. Indian polyvalent ASV covers the spectacled cobra, common krait, Russell's viper and saw-scaled viper. 2. A test dose of ASV should be given first, as it predicts anaphylaxis. 3. Bites of the hump-nosed pit viper are not neutralised by Indian polyvalent ASV. 4. A non-clotting 20WBCT is an indication for ASV. Which statements are correct?

   1. AOnly 1, 3 and 4
   2. BOnly 2, 3 and 4
   3. CAll four: 1, 2, 3 and 4
   4. DOnly 1 and 3

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7. Question 7 · Hard

   A 27-year-old woman is brought to a medical college ICU in Hyderabad on day 3 after an overdose of paracetamol. Despite IV acetylcysteine from day 1, she is now confused and drowsy. After adequate fluid resuscitation, arterial pH is 7.24, INR 5.8, creatinine 2.1 mg/dL and lactate 4.2 mmol/L. What is the most appropriate next step?

   1. AGive vitamin K and observe for 48 hours
   2. BStart haemodialysis to remove paracetamol
   3. CUrgent referral for liver transplantation
   4. DStop acetylcysteine as it has failed

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8. Question 8 · Medium

   A 34-year-old farmer from Nanded who drank an organophosphate insecticide has been fully atropinised: his chest is clear, pulse 108/min, systolic BP above 90 mmHg and pupils no longer pinpoint. However, he still has fasciculations over the chest and thighs and weak neck flexion. Why have these signs persisted?

   1. AHe has developed atropine toxicity
   2. BThe dose of atropine is still too low
   3. CAtropine does not block nicotinic receptors
   4. DThe poison is a pyrethroid, not an organophosphate

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9. Question 9 · Medium

   A 30-year-old man is bitten on the hand by a cobra in Tamil Nadu. An hour later he has bilateral ptosis and difficulty swallowing, with painful swelling of the hand. He has received the first dose of polyvalent ASV. Which adjunct drug is used along with ASV for his paralysis?

   1. AGlycopyrrolate alone
   2. BNeostigmine with atropine
   3. CPralidoxime
   4. DCalcium gluconate

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10. Question 10 · Medium

    A 35-year-old woman is bitten on the ankle by a snake while cutting grass in a village near Mysuru. Her family wants to tie a tight cloth above the knee, cut the wound and suck out the venom before taking her to the PHC. What is the recommended first aid?

    1. ATie a tight tourniquet above the knee to stop spread
    2. BReassure, immobilise the limb and go to hospital
    3. CApply ice packs over the bite
    4. DIncise and suck the bite wound

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11. Question 11 · Medium

    A 30-year-old man who swallowed a large quantity of methadone syrup stolen from a de-addiction clinic in Imphal wakes up promptly after IV naloxone in casualty. Forty-five minutes later he is drowsy again, with a respiratory rate of 7/min and pinpoint pupils. Why has his condition relapsed?

    1. ANaloxone has precipitated opioid withdrawal
    2. BHe has developed tolerance to naloxone
    3. CMethadone is a partial agonist at mu receptors
    4. DNaloxone acts for less time than methadone

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12. Question 12 · Medium

    A 48-year-old man who drinks a bottle of country liquor daily is admitted for a fractured femur in Kanpur. On the third day he becomes disoriented, sees insects crawling on the walls, has coarse tremor, sweating, temperature 38.4 °C and pulse 128/min. Blood glucose and electrolytes are normal. What is the next best step?

    1. AOral disulfiram to deter drinking
    2. BOral naltrexone to curb craving
    3. CIV haloperidol as the only drug
    4. DIV lorazepam titrated to calm sedation

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13. Question 13 · Medium

    A 32-year-old man treated with metronidazole for amoebic dysentery attends a wedding in Goa and drinks two pegs of whisky. Within half an hour he has flushing, throbbing headache, palpitations, nausea and vomiting, and a BP of 90/60 mmHg. Which compound has accumulated to cause this reaction?

    1. AAcetic acid
    2. BFormic acid
    3. CMethyl alcohol
    4. DAcetaldehyde

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14. Question 14 · Medium

    A 22-year-old woman is receiving IV acetylcysteine in casualty in Bengaluru for paracetamol overdose. Twenty minutes into the first infusion she develops flushing, an itchy urticarial rash and mild wheeze; BP is 118/76 mmHg. What is the next best step?

    1. ASwitch to IV desferrioxamine
    2. BPause it, give an antihistamine, then resume
    3. CStop acetylcysteine for good and use oral charcoal
    4. DContinue at the same rate and observe

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15. Question 15 · Easy

    A 28-year-old man admitted to the orthopaedic ward of a hospital in Amritsar for a fracture becomes restless a day later. He is yawning, has watery eyes, a running nose, goose-flesh, dilated pupils, abdominal cramps and diarrhoea. He admits to smoking heroin daily. What is the most likely diagnosis?

    1. AOpioid withdrawal
    2. BAnticholinergic toxicity
    3. CSerotonin syndrome
    4. DAlcohol withdrawal

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16. Question 16 · Medium

    A 20-year-old man is brought to a district hospital in Haryana 2 hours after swallowing grain-preserving tablets. The medical officer reviews four statements about his care: 1. There is no specific antidote for this poison. 2. Death in the first day is usually from refractory shock and arrhythmias. 3. Gas released from his vomitus can harm staff, so the area should be well ventilated. 4. Pralidoxime should be started early. Which statements are correct?

    1. A1, 2 and 3 only
    2. B1, 3 and 4 only
    3. C2 and 4 only
    4. D2 and 3 only

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17. Question 17 · Easy

    A truck driver is brought by the traffic police in Nagpur after a crash, and the police ask for a blood alcohol level. In addition to an anticoagulant, which preservative should be added to the blood sample?

    1. ASaturated sodium chloride
    2. BRectified spirit
    3. CSodium fluoride
    4. DFormalin

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18. Question 18 · Medium

    A 40-year-old woman from Guntur was treated for organophosphate poisoning. On day 3 her secretions have dried and she needs little atropine, but she now has weakness of neck flexion and proximal limb muscles, bilateral ptosis and a falling single breath count. What is the most likely diagnosis?

    1. AOrganophosphate-induced delayed neuropathy
    2. BAtropine toxicity
    3. CGuillain-Barre syndrome
    4. DIntermediate syndrome

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19. Question 19 · Easy

    A 45-year-old farmer from Ratnagiri is bitten on the foot by a snake in a paddy field. At the CHC, 3 mL of his venous blood placed in a new, clean, dry glass tube and left undisturbed for 20 minutes is still liquid when the tube is tilted. What does this result indicate?

    1. ANeurotoxic envenomation needing neostigmine
    2. BVenom-induced coagulopathy needing ASV
    3. CA normal test; observe for 24 hours
    4. DA faulty test, as plastic tubes are needed

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20. Question 20 · Medium

    A 17-year-old girl weighing 50 kg is brought to casualty in Chennai one and a half hours after swallowing 25 tablets of paracetamol 500 mg. She is asymptomatic. A paracetamol level sent on arrival comes back at 2 hours after ingestion. How should this level be used?

    1. APlot the 2-hour level on the nomogram now
    2. BIgnore levels and give charcoal only
    3. CRepeat the level at 4 hours and plot it
    4. DDischarge her if the level is low

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21. Question 21 · Medium

    A 42-year-old woman from Tirunelveli recovered from a Russell's viper bite a year ago, during which she had bleeding gums, a non-clotting 20WBCT and acute kidney injury needing dialysis. She now has fatigue, loss of axillary and pubic hair, amenorrhoea and low sodium. What is the most likely cause?

    1. AChronic kidney disease from the AKI
    2. BHypothyroidism from late serum sickness
    3. CAutoimmune primary adrenal failure
    4. DHypopituitarism from pituitary haemorrhage

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22. Question 22 · Hard

    A 32-year-old man from Assam was bitten on the foot at night and brought to a district hospital with ptosis, ophthalmoplegia and weak breathing. There is no swelling at the bite and the 20WBCT is normal. He received polyvalent ASV, and a neostigmine trial after atropine gave no improvement; he is now on a ventilator. Why did neostigmine fail?

    1. AThe toxin blocked ACh receptors irreversibly
    2. BThe toxin damaged nerve terminals releasing ACh
    3. CThe dose of ASV was too low to bind the toxin
    4. DAtropine blocked the action of neostigmine

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23. Question 23 · Medium

    A 30-year-old man is being treated in a district hospital ICU for organophosphate poisoning with an atropine infusion. Six hours later he is agitated and confused, temperature 39.4 °C, pulse 150/min, skin hot and dry, bowel sounds absent and the bladder palpable. His chest is clear. What is the next best step?

    1. ADouble the atropine infusion rate
    2. BStop the atropine and restart at a lower rate
    3. CGive IV haloperidol to control his agitated delirium
    4. DAdd pralidoxime as a bolus

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24. Question 24 · Hard

    A 4-year-old boy in Kochi is given codeine syrup for pain after a tonsillectomy at the recommended dose. On the second night he is found very drowsy, with a respiratory rate of 6/min and pinpoint pupils. His mother had a similar reaction to codeine after a caesarean section. What best explains his toxicity?

    1. APoor CYP2D6 metaboliser status
    2. BSlow acetylator NAT2 status
    3. CPseudocholinesterase deficiency
    4. DUltra-rapid CYP2D6 conversion to morphine

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25. Question 25 · Medium

    A 26-year-old man is admitted with suspected organophosphate poisoning after being found in a field in Haryana. The physician wants a laboratory test that best reflects the degree of enzyme inhibition at the synapses. Which test should be requested?

    1. ASerum amylase
    2. BRed cell acetylcholinesterase activity
    3. CSerum creatine kinase
    4. DPlasma butyrylcholinesterase activity

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