Poisoning, antidotes and adverse drug reactions

23 Gulf Prometric Pharmacist (DHA, DOH, MOH, SCFHS, QCHP) practice questions on Poisoning, antidotes and adverse drug reactions, part of Clinical Pharmacy and Therapeutics. 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.

1. Question 1 · Medium

   A patient presents with a high anion gap metabolic acidosis, visual disturbance and a history of drinking windscreen washer fluid. Which antidote is appropriate?

   1. ANaloxone
   2. BAcetylcysteine
   3. CFomepizole
   4. DAtropine

   Show answerHide answer

   Answer: C · Fomepizole

   Windscreen washer fluid contains methanol, which alcohol dehydrogenase converts to formic acid, causing acidosis and optic nerve toxicity. Fomepizole inhibits alcohol dehydrogenase and blocks the toxic metabolite formation, and haemodialysis is used in severe cases.

   • A: Naloxone reverses opioids.
   • B: Acetylcysteine is for paracetamol.
   • D: Atropine treats cholinergic poisoning.

   Remember this

   Fomepizole inhibits alcohol dehydrogenase in methanol and ethylene glycol poisoning.

2. Question 2 · Medium

   A patient has bradycardia and hypotension after propranolol overdose, unresponsive to atropine. Which treatment is recommended next?

   1. AVerapamil
   2. BGlucagon
   3. CFlumazenil
   4. DDigoxin

   Show answerHide answer

   Answer: B · Glucagon

   Glucagon raises cyclic AMP through glucagon receptors, bypassing the blocked beta receptors, and increases heart rate and contractility. High-dose insulin euglycaemia therapy is another option. Calcium channel blockers would worsen the problem.

   • A: Verapamil would cause further bradycardia.
   • C: Flumazenil acts on benzodiazepine receptors.
   • D: Digoxin is also bradycardic in toxic settings and is not an antidote.

   Remember this

   Glucagon is the first-line antidote for beta-blocker overdose with bradycardia and hypotension.

3. Question 3 · Medium

   Which statement about activated charcoal in a lithium overdose is correct?

   1. ACharcoal binds lithium only after a gastric lavage procedure
   2. BCharcoal should be given with sorbitol only
   3. CCharcoal is the treatment of choice
   4. DCharcoal binds lithium poorly and is not recommended

   Show answerHide answer

   Answer: D · Charcoal binds lithium poorly and is not recommended

   Lithium is a small ion that is not adsorbed well to charcoal. Management is with intravenous saline, monitoring of levels, and haemodialysis for severe toxicity. Charcoal is likewise ineffective for iron and alcohols.

   • A: Gastric lavage does not alter adsorption.
   • B: Sorbitol does not make charcoal bind lithium.
   • C: Charcoal is not the treatment of choice.

   Remember this

   Activated charcoal does not bind lithium, iron or alcohols.

4. Question 4 · Medium

   A patient of Han Chinese ancestry with chronic kidney disease is about to start allopurinol for gout. Which pre-treatment test is advised?

   1. AHLA-B*57:01 genotype
   2. BHLA-B*58:01 genotype
   3. CHLA-B*15:02 genotype
   4. DGlucose-6-phosphate dehydrogenase activity

   Show answerHide answer

   Answer: B · HLA-B*58:01 genotype

   HLA-B*58:01 is strongly associated with severe allopurinol hypersensitivity, including Stevens-Johnson syndrome, and the risk is higher with renal impairment and in people of Han Chinese, Thai or Korean ancestry. Testing before starting is advised in these groups.

   • A: HLA-B*57:01 is linked to abacavir.
   • C: HLA-B*15:02 is linked to carbamazepine.
   • D: G6PD testing guides rasburicase and dapsone use, not allopurinol.

   Remember this

   Test for HLA-B*58:01 before allopurinol in high-risk ancestries.

5. Question 5 · Easy

   Which antidote reverses the anticoagulant effect of warfarin?

   1. ATranexamic acid
   2. BIdarucizumab
   3. CProtamine sulfate
   4. DVitamin K

   Show answerHide answer

   Answer: D · Vitamin K

   Warfarin blocks vitamin K epoxide reductase, so the clotting factors II, VII, IX and X are made in a non-functional form. Vitamin K restores their synthesis over several hours. Prothrombin complex concentrate is added when bleeding is serious.

   • A: Tranexamic acid is an antifibrinolytic, not an anticoagulant antidote.
   • B: Idarucizumab reverses dabigatran.
   • C: Protamine reverses heparin.

   Remember this

   Vitamin K is the antidote to warfarin; PCC is added for major bleeding.

6. Question 6 · Hard

   A patient has taken a large amount of verapamil and has hypotension and bradycardia that have not responded to fluids and atropine. Which treatment should be started next?

   1. AIntravenous digoxin to improve myocardial contractility
   2. BOral activated charcoal as the only treatment
   3. CIntravenous calcium with high-dose insulin and glucose
   4. DIntravenous propranolol to control the heart rhythm

   Answer and explanation in LearnFree account

7. Question 7 · Hard

   A patient taking apixaban has a life-threatening gastrointestinal haemorrhage. Which reversal approach is appropriate?

   1. AProtamine sulfate in a dose matched to apixaban
   2. BAndexanet alfa, or 4-factor PCC if it is unavailable
   3. COral vitamin K alone given for three days
   4. DIdarucizumab, the specific antidote for factor Xa inhibitors

   Answer and explanation in LearnFree account

8. Question 8 · Medium

   A patient arrives 10 hours after a single large paracetamol overdose. A plasma level is not yet available. What is the best action?

   1. AObserve for liver signs before any treatment
   2. BWait for the 4-hour level before deciding whether to treat at all
   3. CStart acetylcysteine at once without waiting for the level
   4. DGive activated charcoal and discharge

   Answer and explanation in LearnFree account

9. Question 9 · Easy

   What is the main purpose of post-marketing adverse drug reaction reporting to the national pharmacovigilance centre?

   1. ATo audit the sales volume of every community pharmacy
   2. BTo replace the need for premarketing trials
   3. CTo set the retail price of a medicine
   4. DTo detect new or rare safety signals missed in trials

   Answer and explanation in LearnFree account

10. Question 10 · Medium

    A farm worker has salivation, lacrimation, bronchorrhoea, constricted pupils and muscle fasciculations after spraying an insecticide. Which treatment is the most appropriate?

    1. AAtropine together with pralidoxime
    2. BNeostigmine to reinforce the cholinergic effect
    3. CNaloxone to reverse the muscle weakness
    4. DPhysostigmine alone to reverse the toxicity

    Answer and explanation in LearnFree account

11. Question 11 · Hard

    A patient presents 12 hours after a single paracetamol overdose with a plasma level of 50 mg/L. The treatment line is 150 mg/L at 4 hours and it falls with a 4-hour half-life. What should be done?

    1. ARepeat the level at 16 hours before making a decision
    2. BStart acetylcysteine: 50 mg/L is above the 12-hour line of about 37 mg/L
    3. CDo not treat, because 50 mg/L is below the standard 4-hour line of 150 mg/L
    4. DGive activated charcoal and no acetylcysteine

    Answer and explanation in LearnFree account

12. Question 12 · Easy

    A family is brought in with headache, nausea and confusion after running a charcoal heater in a closed room. Carbon monoxide poisoning is suspected. What is the first treatment?

    1. AHigh-flow 100% oxygen
    2. BOral activated charcoal
    3. CIntravenous methylene blue
    4. DIntravenous sodium thiosulfate

    Answer and explanation in LearnFree account

13. Question 13 · Medium

    A fire survivor has smoke inhalation, severe lactic acidosis and shock. Cyanide poisoning is suspected. Which antidote is preferred?

    1. AMethylene blue
    2. BAcetylcysteine
    3. CFomepizole
    4. DHydroxocobalamin

    Answer and explanation in LearnFree account

14. Question 14 · Easy

    Which antidote reverses benzodiazepine-induced sedation?

    1. ANaloxone
    2. BPralidoxime
    3. CFlumazenil
    4. DSugammadex

    Answer and explanation in LearnFree account

15. Question 15 · Hard

    A patient with salicylate poisoning has a level of 650 mg/L, tinnitus and a respiratory alkalosis with metabolic acidosis. Urinary alkalinisation with sodium bicarbonate is not raising the urine pH. What is the most likely problem?

    1. AHypocalcaemia
    2. BHypernatraemia
    3. CUncorrected hypokalaemia
    4. DHypermagnesaemia

    Answer and explanation in LearnFree account

16. Question 16 · Medium

    A toddler swallowed ferrous sulfate tablets and has vomiting, hypotension and a high serum iron concentration. Which treatment is indicated?

    1. AIntravenous deferoxamine
    2. BAcetylcysteine
    3. CFlumazenil
    4. DActivated charcoal

    Answer and explanation in LearnFree account

17. Question 17 · Medium

    A patient who took long-acting morphine tablets has respiratory depression that improves after naloxone 0.4 mg but returns after 40 minutes. What is the best plan?

    1. AGive repeated doses or an infusion with close monitoring
    2. BStop monitoring because the antidote worked
    3. CSwitch to flumazenil, which has a longer duration than naloxone
    4. DGive a single dose only and discharge

    Answer and explanation in LearnFree account

18. Question 18 · Medium

    During an acetylcysteine infusion a patient develops flushing, urticaria and mild wheeze. What is the appropriate management?

    1. AStop acetylcysteine permanently and use charcoal
    2. BDouble the infusion rate to finish sooner
    3. CPause the infusion, give an antihistamine, restart more slowly
    4. DGive intramuscular adrenaline immediately in every case of this kind

    Answer and explanation in LearnFree account

19. Question 19 · Easy

    Which type of adverse drug reaction is predictable, dose-dependent and related to the drug's pharmacology?

    1. AType A
    2. BType B (bizarre)
    3. CType C (chronic)
    4. DType D (delayed)

    Answer and explanation in LearnFree account

20. Question 20 · Medium

    A patient has taken a mixed overdose of amitriptyline and diazepam and is drowsy (GCS 9). Why should flumazenil be avoided?

    1. AIt causes severe prolonged hypoglycaemia
    2. BIt can precipitate seizures in tricyclic poisoning
    3. CIt deepens respiratory depression at standard doses
    4. DIt binds amitriptyline in the gut and blocks absorption

    Answer and explanation in LearnFree account

21. Question 21 · Medium

    Which tool is widely used to assess the likelihood that a drug caused an adverse reaction?

    1. ANaranjo algorithm
    2. BCockcroft-Gault equation
    3. CChild-Pugh score
    4. DApgar score

    Answer and explanation in LearnFree account

22. Question 22 · Hard

    A 70 kg patient has a serum digoxin concentration of 8 ng/mL with life-threatening arrhythmias. Using vials = (concentration in ng/mL x weight in kg) / 100, how many digoxin-specific Fab vials are needed?

    1. A6
    2. B3
    3. C8
    4. D12

    Answer and explanation in LearnFree account

23. Question 23 · Medium

    A patient on sertraline is given tramadol and a day later has agitation, clonus, hyperreflexia and a temperature of 39 C. What is the most likely diagnosis and first step?

    1. ASerotonin syndrome; stop both drugs and give supportive care
    2. BMalignant hyperthermia; give dantrolene and nothing else
    3. CAnaphylaxis; give adrenaline and fluids
    4. DNeuroleptic malignant syndrome; give haloperidol at once and cool

    Answer and explanation in LearnFree account