Clinical Pharmacology and Drug Toxicity — MCQs

Clinical Pharmacology and Drug Toxicity Indian Medical PG Practice Questions and MCQs

Question 661: Consider the following regarding salicylate poisoning : I. Arterial pH of 7.25 , anion gap of 18 mmol / L II. Arterial pH of 7.25 , anion gap of 10 mmol / L III. pCO2 of 20 mm Hg IV. pCO2 of 48 mm Hg Which disturbance is likely to be encountered?

A. II and III
B. II and IV
C. I and III (Correct Answer)
D. I and IV

Explanation: ***I and III*** - Salicylate poisoning typically presents with a **mixed acid-base disorder** consisting of primary **respiratory alkalosis** and primary **metabolic acidosis with an increased anion gap** [1]. - A pH of 7.25 with an anion gap of 18 mmol/L (normal range 8-12 mmol/L) indicates **metabolic acidosis with an increased anion gap**, while a pCO2 of 20 mmHg (normal range 35-45 mmHg) indicates **respiratory alkalosis** [2]. *II and III* - An anion gap of 10 mmol/L is within the normal range, which is inconsistent with the **metabolic acidosis with increased anion gap** expected in salicylate poisoning [1]. - While pCO2 of 20 mmHg indicates respiratory alkalosis, the normal anion gap makes this combination less likely for salicylate poisoning. *II and IV* - An anion gap of 10 mmol/L is within the normal range, which does not reflect the typical **anion gap metabolic acidosis** seen in salicylate poisoning. - A pCO2 of 48 mmHg indicates respiratory acidosis, which is generally not the primary respiratory disturbance in salicylate poisoning; rather, **respiratory alkalosis** due to direct stimulation of the respiratory center is more characteristic [1]. *I and IV* - While an anion gap of 18 mmol/L is consistent with **anion gap metabolic acidosis**, a pCO2 of 48 mmHg indicates respiratory acidosis. - The classic picture of salicylate poisoning includes **respiratory alkalosis** due to direct stimulation of the respiratory center, not respiratory acidosis [1].

Question 662: A 45 year old farmer came with accidental consumption of a pesticide. He complained of frequent urination and excessive salivation. Which one of the following toxidromes is most likely to be associated with this poisoning?

A. Adrenergic
B. Cholinergic (Correct Answer)
C. Hypnotic
D. Serotonergic

Explanation: ***Cholinergic*** The patient's symptoms of frequent urination and excessive salivation, along with accidental pesticide consumption, are classic signs of **organophosphate poisoning**, which falls under the **cholinergic toxidrome** [1, 2]. This toxidrome is characterized by excessive stimulation of the **cholinergic system**, leading to symptoms memorized by the acronyms **SLUDGE** (Salivation, Lacrimation, Urination, Defecation, Gastrointestinal upset, Emesis) and **DUMBBELS** (Diarrhea, Urination, Miosis, Bradycardia, Bronchorrhea, Emesis, Lacrimation, Salivation) [1]. *Adrenergic* The adrenergic toxidrome is associated with sympathetic overactivity, leading to symptoms like **tachycardia**, **hypertension**, **mydriasis**, agitation, and hyperthermia. These symptoms are opposite to the parasympathetic overactivity observed in this patient. *Hypnotic* The hypnotic toxidrome typically presents with **CNS depression**, including **sedation**, **respiratory depression**, **bradycardia**, and **hypotension**. This toxidrome does not match the patient's symptoms of excessive salivation and frequent urination. *Serotonergic* The serotonergic toxidrome (serotonin syndrome) is characterized by a triad of mental status changes, autonomic hyperactivity (e.g., **tachycardia**, **hypertension**, hyperthermia), and neuromuscular abnormalities (e.g., **hyperreflexia**, clonus). The patient's presentation does not align with these hallmark features.

Question 663: Which one of the following prevents gastrointestinal absorption of thallium?

A. Calcium carbonate
B. Potassium permanganate
C. Penicillamine
D. Prussian blue (Correct Answer)

Explanation: ***Prussian blue*** - **Prussian blue** (ferric hexacyanoferrate) acts as an ion exchanger in the gastrointestinal tract, binding to thallium and preventing its absorption. - This complex of thallium and Prussian blue is then **excreted in the feces**, reducing systemic toxicity. *Calcium carbonate* - **Calcium carbonate** is an antacid primarily used to neutralize stomach acid or as a calcium supplement. - It does not specifically bind to or prevent the absorption of **thallium**. *Potassium permanganate* - **Potassium permanganate** is a strong oxidizing agent sometimes used for gastric lavage in certain poisonings. - It does not form a stable, non-absorbable complex with **thallium** to prevent its gastrointestinal uptake. *Penicillamine* - **Penicillamine** is a chelating agent used for heavy metal poisoning, such as copper (in Wilson's disease) or lead. - While it can chelate some metals, its primary mechanism involves forming soluble complexes that are excreted renally, rather than directly preventing **gastrointestinal absorption** of thallium.

Question 664: Fomepizole is an antidote used to treat poisoning from which of the following substances? I. Methanol II. Digoxin III. Cocaine IV. Ethylene glycol Select the correct answer using the code given below :

A. III and IV
B. I and II
C. I and IV (Correct Answer)
D. II and III

Explanation: ***I and IV*** - **Fomepizole** is a competitive inhibitor of **alcohol dehydrogenase**, the enzyme that metabolizes both methanol and ethylene glycol into toxic metabolites [1]. - For **methanol** poisoning: Prevents conversion to **formic acid**, which causes metabolic acidosis and optic nerve damage [2]. - For **ethylene glycol** poisoning: Prevents conversion to **glycolic acid and oxalic acid**, which cause metabolic acidosis, renal failure, and calcium oxalate crystal deposition [1]. - Fomepizole is the preferred antidote over ethanol due to its safer profile and ease of administration. *III and IV* - While ethylene glycol (IV) is correctly identified, **cocaine** (III) poisoning is not treated with fomepizole. - Cocaine toxicity management involves supportive care, benzodiazepines for agitation and seizures, and management of cardiovascular complications (hypertension, arrhythmias). - Fomepizole has no role in cocaine overdose as the toxic mechanism does not involve alcohol dehydrogenase. *I and II* - While methanol (I) is correctly identified, **digoxin** (II) poisoning is not treated with fomepizole. - Digoxin toxicity is managed with **digoxin-specific antibody fragments (Digoxin Fab)**, which bind and neutralize digoxin. - Fomepizole's mechanism of alcohol dehydrogenase inhibition is irrelevant to digoxin toxicity. *II and III* - Neither **digoxin** (II) nor **cocaine** (III) poisoning is treated with fomepizole. - Both substances have different toxic mechanisms unrelated to alcohol dehydrogenase. - Digoxin requires Fab fragments; cocaine requires supportive care and symptomatic management.

Question 665: Which one of the following is used to reverse the anticoagulant effects of Dabigatran?

A. Desferrioxamine
B. Protamine
C. Glucarpidase
D. Idarucizumab (Correct Answer)

Explanation: ***Idarucizumab*** - **Idarucizumab** is a **monoclonal antibody fragment** specifically designed to bind to dabigatran and its active metabolites. - This binding neutralizes the anticoagulant effect of dabigatran, providing **rapid reversal** in emergency situations. *Desferrioxamine* - **Desferrioxamine** is a **chelating agent** used to treat **iron poisoning**. - It works by binding to iron in the bloodstream, facilitating its excretion from the body, and has no effect on anticoagulant drugs. *Protamine* - **Protamine** is used to reverse the anticoagulant effects of **heparin** by forming a stable salt with it. - It is **not effective** for reversing the effects of direct oral anticoagulants like dabigatran. *Glucarpidase* - **Glucarpidase** is an enzyme used to reduce toxic plasma methotrexate concentrations in patients with impaired renal function. - It catalyzes the hydrolysis of methotrexate into inactive metabolites and has **no role** in anticoagulant reversal.

Question 666: Which one of the following is an antidote for Rivaroxaban and Apixaban, when reversal of anticoagulation is needed due to uncontrolled bleeding?

A. Hydroxocobalamin
B. Glucarpidase
C. Andexanet Alfa (Correct Answer)
D. Idarucizumab

Explanation: ***Andexanet Alfa*** - **Andexanet Alfa** is a **modified recombinant factor Xa molecule** that acts as a decoy to bind and sequester direct factor Xa inhibitors like rivaroxaban and apixaban. - It is specifically indicated for the reversal of anticoagulation in patients treated with **rivaroxaban** or **apixaban** experiencing life-threatening or uncontrolled bleeding [1]. *Hydroxocobalamin* - **Hydroxocobalamin** is an antidote for **cyanide poisoning**, not for anticoagulant reversal. - It works by binding to cyanide to form cyanocobalamin, which can be excreted, thereby detoxifying the patient. *Glucarpidase* - **Glucarpidase** is used to rapidly lower **methotrexate concentrations** in patients with delayed methotrexate elimination and associated toxicity. - It is an enzyme that hydrolyzes methotrexate into inactive metabolites, facilitating its clearance. *Idarucizumab* - **Idarucizumab** is a specific reversal agent for **dabigatran**, a direct thrombin inhibitor. - It is a monoclonal antibody fragment that binds to dabigatran with high affinity, neutralizing its anticoagulant effect.

Question 667: Which of the following can be used for the management of severe hyperkalaemia? I. Intravenous calcitonin II. Intravenous sodium bicarbonate III. Oral sodium polystyrene sulphate IV. Intravenous calcium gluconate

A. I and II only
B. I and IV only
C. I, II and IV
D. II, III and IV (Correct Answer)

Explanation: ***II, III and IV*** - **Intravenous sodium bicarbonate** helps shift potassium into cells, primarily used in cases of metabolic acidosis. - **Oral sodium polystyrene sulfonate** (Kayexalate) is a cation-exchange resin that binds potassium in the gut, facilitating its excretion. - **Intravenous calcium gluconate** does not lower serum potassium but stabilizes the cardiac membrane, protecting against life-threatening arrhythmias. *I and II only* - **Intravenous calcitonin** is used in hypercalcemia to lower calcium levels and is not indicated for the management of hyperkalemia. - While intravenous sodium bicarbonate is used, relying on it alone with calcitonin would be insufficient and inappropriate. *I and IV only* - **Intravenous calcitonin** is not a treatment for hyperkalemia. - Although intravenous calcium gluconate is crucial for cardiac stabilization, it does not address the underlying hyperkalemia directly, making this option incomplete and incorrect. *'I, II and IV* - **Intravenous calcitonin** has no role in the management of hyperkalemia. - While intravenous sodium bicarbonate and calcium gluconate are important, the inclusion of calcitonin makes this option incorrect.

Question 668: Ulipristal acetate (progesterone receptor modulator) should not be prescribed as emergency contraceptive in women with

A. liver dysfunction (Correct Answer)
B. glaucoma
C. coagulopathy
D. kidney failure

Explanation: ***Correct: liver dysfunction*** - **Ulipristal acetate** is extensively metabolized in the **liver** by the CYP450 enzyme system, predominantly CYP3A4. - In individuals with **severe hepatic impairment**, the metabolism of ulipristal acetate can be impaired, leading to increased plasma concentrations and potential adverse effects. - **Severe liver dysfunction** is a documented contraindication in product labeling. *Incorrect: glaucoma* - There is **no known contraindication** for ulipristal acetate use in individuals with **glaucoma**. - Its mechanism of action primarily involves progesterone receptors and does not directly impact intraocular pressure. *Incorrect: coagulopathy* - Ulipristal acetate does **not significantly affect blood coagulation** parameters or platelet function. - It is not contraindicated in individuals with **coagulopathy**, unlike some estrogen-containing contraceptives. *Incorrect: kidney failure* - While urinary excretion of ulipristal acetate metabolites occurs, the **primary elimination pathway is fecal** (approximately 90%). - **Kidney failure** is not considered a contraindication, and dose adjustments are generally not required.

Question 669: Which of the following is a rare vaccine reaction known to occur with BCG vaccine in immunocompetent individuals?

A. Guillain-Barre syndrome
B. Osteitis (Correct Answer)
C. Suppurative lymphadenitis
D. Disseminated infection

Explanation: ***Osteitis*** - **Osteitis** (inflammation of bone) is a **rare complication** of the BCG vaccine, occurring in **immunocompetent individuals**, particularly infants. - Incidence: approximately **1-30 cases per million doses**. - It results from the **dissemination of live attenuated *Mycobacterium bovis*** (the strain used in BCG) to bone tissue. - Typically presents months after vaccination with localized bone pain and swelling. *Guillain-Barré syndrome* - **Guillain-Barré syndrome** is a rare neurological disorder characterized by rapid-onset muscle weakness. - While it can be triggered by various infections and, rarely, by some vaccines (e.g., influenza vaccine), it is **not specifically associated with the BCG vaccine**. *Suppurative lymphadenitis* - **Suppurative lymphadenitis** (inflammation and pus formation in lymph nodes) is a **relatively common adverse reaction** to the BCG vaccine, not a rare one. - Incidence: **0.01-4.3%** of vaccinees. - It typically occurs in regional lymph nodes draining the injection site and usually resolves with conservative management or needle aspiration. *Disseminated infection* - **Disseminated BCG infection** is an **extremely rare** complication (0.06-1.56 per million doses). - It occurs **primarily in immunocompromised individuals** (e.g., severe combined immunodeficiency, HIV). - This is a contraindication-related complication rather than a typical vaccine reaction in the general population. - The question specifies immunocompetent individuals, making **osteitis** the most appropriate answer as it represents the classic rare complication in normal hosts.

Question 670: Which of the following is an absolute contraindication for combined contraceptive oral pills ?

A. Migraine without aura
B. Previous history of thrombo-embolism (Correct Answer)
C. Diabetes mellitus
D. Gall bladder disease

Explanation: ***Previous history of thrombo-embolism*** - A history of **thromboembolism** significantly increases the risk of recurrent events with combined oral contraceptive pills (COCs) due to their procoagulant effects [1, 2]. - COCs contain **estrogen**, which can enhance the synthesis of clotting factors and decrease natural anticoagulants, making them absolutely contraindicated in this setting [1]. *Migraine without aura* - **Migraine without aura** is generally considered a relative contraindication or a condition requiring careful consideration, not an absolute contraindication, for combined oral contraceptive pills. - The risk of **stroke** is slightly elevated in women with migraine without aura using COCs, but it is not as high as with migraine with aura. *Diabetes mellitus* - **Diabetes mellitus** itself is not an absolute contraindication for combined oral contraceptive pills, especially if it is well-controlled and there are no vascular complications. - However, in cases of diabetes with **vascular complications** (e.g., nephropathy, retinopathy, neuropathy) or of >20 years' duration, COCs are generally contraindicated. *Gall bladder disease* - While combined oral contraceptive pills can increase the risk of **gallstone formation**, especially in susceptible individuals, it is not considered an absolute contraindication. - The effect is linked to **estrogen-induced changes** in bile composition, but careful monitoring is usually sufficient rather than absolute avoidance.

Practice by Chapter

Principles of Clinical Pharmacology

Practice Questions

Therapeutic Drug Monitoring

Practice Questions

Drug Toxicity and Overdose

Practice Questions

Antidotes and Their Applications

Practice Questions

Management of Drug Poisoning

Practice Questions

Drug-Induced Liver Injury

Practice Questions

Drug-Induced Kidney Injury

Practice Questions

Drug-Induced Blood Dyscrasias

Practice Questions

Drug-Induced QT Prolongation

Practice Questions

Pharmacovigilance

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free