SMLE Pharmacology 3 — Questions and Answers
Question 1: A patient presents with organophosphate poisoning showing excessive salivation, lacrimation, urination, diarrhoea, and miosis. What is the antidote?
- Naloxone
- Atropine and pralidoxime (Correct answer)
- Physostigmine
- Flumazenil
Correct answer: Atropine and pralidoxime
Organophosphate poisoning causes cholinergic crisis by irreversibly inhibiting acetylcholinesterase. Atropine (muscarinic antagonist) treats secretions and bradycardia, while pralidoxime (2-PAM) reactivates acetylcholinesterase if given early (before 'ageing' of the enzyme-inhibitor complex).
Question 2: A patient on long-term corticosteroids is to undergo surgery. What perioperative consideration is essential?
- Abrupt discontinuation of steroids before surgery
- Stress-dose steroids (hydrocortisone) perioperatively (Correct answer)
- No dose adjustment needed
- Switch to NSAIDs before surgery
Correct answer: Stress-dose steroids (hydrocortisone) perioperatively
Chronic corticosteroid use suppresses the hypothalamic-pituitary-adrenal (HPA) axis. During surgical stress, the adrenal glands cannot mount an appropriate cortisol response, risking adrenal crisis. Stress-dose hydrocortisone (50-100 mg IV) is given perioperatively.
Question 3: Which antiemetic is the drug of choice for chemotherapy-induced nausea and vomiting?
- Metoclopramide
- Ondansetron (Correct answer)
- Cyclizine
- Domperidone
Correct answer: Ondansetron
Ondansetron (a 5-HT3 receptor antagonist) is first-line for chemotherapy-induced nausea and vomiting (CINV). It blocks serotonin receptors in the chemoreceptor trigger zone and vagal afferents. For highly emetogenic chemotherapy, it is combined with dexamethasone and aprepitant (NK1 antagonist).
Question 4: A patient is started on amiodarone for atrial fibrillation. Which organ systems require monitoring due to amiodarone toxicity?
- Kidneys and pancreas
- Thyroid, liver, lungs, and eyes (Correct answer)
- Brain and spinal cord
- Bone marrow and spleen
Correct answer: Thyroid, liver, lungs, and eyes
Amiodarone has a wide toxicity profile requiring monitoring of: thyroid (hypo/hyperthyroidism due to iodine content), liver (hepatotoxicity), lungs (pulmonary fibrosis), eyes (corneal microdeposits, optic neuropathy), and skin (photosensitivity, blue-grey discolouration).
Question 5: What is the mechanism of action of omeprazole?
- H2 receptor antagonist
- Irreversible proton pump inhibitor (Correct answer)
- Muscarinic receptor antagonist
- Prostaglandin analogue
Correct answer: Irreversible proton pump inhibitor
Omeprazole irreversibly inhibits the hydrogen-potassium ATPase (proton pump) on the luminal surface of parietal cells in the stomach. This blocks the final common pathway of acid secretion, providing potent and sustained acid suppression.
Question 6: A patient develops methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia. What is the drug of choice?
- Flucloxacillin
- Vancomycin (Correct answer)
- Ciprofloxacin
- Amoxicillin-clavulanate
Correct answer: Vancomycin
Vancomycin is the gold standard treatment for MRSA bacteraemia. It acts by inhibiting cell wall synthesis by binding to D-Ala-D-Ala terminus of peptidoglycan precursors. Trough levels should be monitored (15-20 μg/mL for serious infections). Daptomycin is an alternative.
SMLE Pharmacology 3
A patient presents with organophosphate poisoning showing excessive salivation, lacrimation, urination, diarrhoea, and miosis.
What is the antidote?