Thiazide diuretics – Chlorthiazide MCQs With Answer

Thiazide diuretics – Chlorthiazide MCQs With Answer

Thiazide diuretics, especially chlorthiazide, are cornerstone antihypertensive and diuretic agents studied in B. Pharm pharmacology courses. This concise introduction covers chlorthiazide’s mechanism of action at the renal distal convoluted tubule (inhibition of the Na-Cl cotransporter), pharmacokinetics, therapeutic uses (hypertension, edema, nephrolithiasis), and common adverse effects including hypokalemia, hyponatremia, hypercalcemia, metabolic alkalosis, and hyperuricemia. Emphasis is placed on drug interactions, contraindications (sulfonamide sensitivity, pregnancy considerations), dosing principles and monitoring of electrolytes. The MCQs focus on mechanism of action, adverse effect profiles, laboratory monitoring, comparative pharmacology with thiazide-like agents, and clinical case scenarios to strengthen pharmacotherapeutic decision-making. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which membrane transporter is primarily inhibited by chlorthiazide in the distal convoluted tubule?

• Na+/K+ ATPase
• ENaC (epithelial sodium channel)
• Na+-Cl− cotransporter (NCC)
• Na+-H+ exchanger (NHE3)

Correct Answer: Na+-Cl− cotransporter (NCC)

Q2. Chlorthiazide produces an increase in serum calcium primarily because it:

• increases bone resorption
• decreases renal calcium excretion by enhancing distal tubular calcium reabsorption
• blocks intestinal calcium absorption
• stimulates parathyroid hormone secretion

Correct Answer: decreases renal calcium excretion by enhancing distal tubular calcium reabsorption

Q3. Which adverse effect is most characteristically associated with thiazide diuretics like chlorthiazide?

• Hypokalemia
• Hyperkalemia
• Hypocalcemia
• Type I renal tubular acidosis

Correct Answer: Hypokalemia

Q4. One paradoxical therapeutic use of thiazide diuretics is in nephrogenic diabetes insipidus because they:

• directly stimulate ADH receptors in the collecting duct
• reduce free water clearance by increasing proximal tubular reabsorption of sodium and water
• increase urine osmolarity by blocking aquaporin channels
• inhibit vasopressin synthesis in the hypothalamus

Correct Answer: reduce free water clearance by increasing proximal tubular reabsorption of sodium and water

Q5. Which laboratory abnormality commonly occurs with chlorthiazide therapy and may exacerbate digoxin toxicity?

• Hypernatremia
• Hypokalemia
• Hypermagnesemia
• Hypocalcemia

Correct Answer: Hypokalemia

Q6. Chlorothiazide (chlorthiazide) differs from chlorthalidone primarily in that chlorthiazide:

• has a much longer half-life than chlorthalidone
• is available for intravenous administration
• is not a sulfonamide derivative
• causes hyperkalemia rather than hypokalemia

Correct Answer: is available for intravenous administration

Q7. Which of the following conditions is a classic indication for chlorthiazide therapy?

• Acute tubular necrosis
• Hypovolemic shock
• Essential hypertension
• Severe hyperkalemia

Correct Answer: Essential hypertension

Q8. Thiazide diuretics can precipitate gout because they:

• increase uric acid synthesis in the liver
• reduce uric acid secretion in the proximal tubule
• increase purine breakdown in muscle
• promote uric acid renal excretion

Correct Answer: reduce uric acid secretion in the proximal tubule

Q9. Which patient characteristic predicts reduced efficacy of chlorthiazide as a diuretic?

• GFR less than 30 mL/min/1.73 m2
• Age under 40 years
• Mild hypertension responsive to ACE inhibitors
• Concurrent use of low-dose aspirin

Correct Answer: GFR less than 30 mL/min/1.73 m2

Q10. A common metabolic disturbance produced by thiazide diuretics is:

• metabolic acidosis with hyperkalemia
• metabolic alkalosis with hypokalemia
• respiratory acidosis
• non-anion gap metabolic acidosis

Correct Answer: metabolic alkalosis with hypokalemia

Q11. Which drug interaction is important when chlorthiazide is co-prescribed with lithium?

• Thiazides increase lithium renal clearance causing low lithium levels
• Thiazides reduce lithium renal clearance leading to lithium toxicity
• Thiazides bind lithium in the gut reducing absorption
• There is no clinically relevant interaction

Correct Answer: Thiazides reduce lithium renal clearance leading to lithium toxicity

Q12. Which statement about the antihypertensive mechanism of chronic thiazide therapy is most accurate?

• Long-term blood pressure lowering is solely due to diuresis and volume reduction
• Long-term effect involves decreased peripheral vascular resistance in addition to natriuresis
• They act centrally to reduce sympathetic outflow
• They increase cardiac output to lower blood pressure

Correct Answer: Long-term effect involves decreased peripheral vascular resistance in addition to natriuresis

Q13. Which electrolyte change would you monitor closely when starting a patient on chlorthiazide?

• Serum potassium and sodium
• Serum phosphate and magnesium only
• Serum iron levels
• Serum chloride is not affected

Correct Answer: Serum potassium and sodium

Q14. Chlorthiazide is chemically classified as which of the following?

• Loop diuretic (sulfonylurea family)
• Thiazide diuretic (benzothiadiazine sulfonamide)
• Potassium-sparing diuretic (spironolactone class)
• Carbonic anhydrase inhibitor

Correct Answer: Thiazide diuretic (benzothiadiazine sulfonamide)

Q15. Which of these adverse effects of thiazides is especially relevant to diabetic patients?

• Thiazides cause significant hypoglycemia
• Thiazides may cause hyperglycemia and impaired glucose tolerance
• Thiazides increase insulin secretion dramatically
• Thiazides prevent diabetic nephropathy

Correct Answer: Thiazides may cause hyperglycemia and impaired glucose tolerance

Q16. A patient on chlorthiazide develops muscle weakness and ECG changes. The most likely electrolyte abnormality is:

• Hyperkalemia
• Hypokalemia
• Hypercalcemia without potassium change
• Hyponatremia only

Correct Answer: Hypokalemia

Q17. Which of the following is a contraindication or caution for chlorthiazide use?

• History of severe sulfonamide allergy
• Mild seasonal allergies
• Well-controlled Type 2 diabetes with normal renal function
• Stable hypothyroidism on replacement therapy

Correct Answer: History of severe sulfonamide allergy

Q18. Why do thiazides reduce the risk of calcium-containing kidney stones?

• They increase urinary citrate excretion
• They cause hypercalciuria
• They decrease urinary calcium excretion
• They alkalinize urine preventing calcium precipitation

Correct Answer: They decrease urinary calcium excretion

Q19. Which of the following drugs reduces the antihypertensive efficacy of chlorthiazide via prostaglandin inhibition?

• ACE inhibitors
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Calcium channel blockers
• Statins

Correct Answer: Nonsteroidal anti-inflammatory drugs (NSAIDs)

Q20. In overdose, which clinical feature would be most expected with chlorthiazide toxicity?

• Severe hyperkalemia and bradycardia
• Profound diuresis with volume depletion, hypotension, and electrolyte disturbances
• Acute bronchospasm unresponsive to bronchodilators
• CNS excitation with seizures due to sodium overload

Correct Answer: Profound diuresis with volume depletion, hypotension, and electrolyte disturbances

Q21. Which monitoring parameter is essential when combining an ACE inhibitor with chlorthiazide?

• Liver function tests only
• Serum potassium and blood pressure
• Prothrombin time
• Pulmonary function tests

Correct Answer: Serum potassium and blood pressure

Q22. Which thiazide-like drug is often used when renal function is reduced because it remains effective at lower GFRs?

• Chlorthiazide
• Hydrochlorothiazide
• Metolazone
• Spironolactone

Correct Answer: Metolazone

Q23. The mechanism by which thiazides cause hyponatremia most commonly involves:

• Excessive intracellular sodium accumulation
• Impaired water excretion combined with natriuresis leading to dilutional hyponatremia
• Direct blockade of ADH receptors
• Increased intestinal sodium loss

Correct Answer: Impaired water excretion combined with natriuresis leading to dilutional hyponatremia

Q24. Which of the following best describes the effect of chlorthiazide on urinary potassium excretion?

• It decreases potassium excretion by blocking distal K+ channels
• It increases potassium excretion indirectly by increasing distal sodium delivery
• It has no effect on potassium handling
• It causes hyperkalemia by inhibiting aldosterone

Correct Answer: It increases potassium excretion indirectly by increasing distal sodium delivery

Q25. For a B. Pharm student, the most important counseling point about chlorthiazide is:

• Take with a high-potassium diet and report muscle weakness or palpitations
• Take it only when severe pain occurs
• It cures gout permanently
• No monitoring is required during therapy

Correct Answer: Take with a high-potassium diet and report muscle weakness or palpitations

Q26. In a patient with both hypertension and osteoporosis risk, why might a thiazide like chlorthiazide be advantageous?

• They increase urinary calcium loss worsening bone loss
• They reduce urinary calcium excretion which may help preserve bone mineral density
• They directly stimulate osteoclast activity
• They prevent vitamin D activation

Correct Answer: They reduce urinary calcium excretion which may help preserve bone mineral density

Q27. Which pharmacokinetic property is true of chlorthiazide compared with longer-acting thiazide-like agents?

• Chlorthiazide has a longer half-life and greater potency than chlorthalidone
• Chlorthiazide is shorter-acting and often requires more frequent dosing than chlorthalidone
• Chlorthiazide is not absorbed orally
• Chlorthiazide accumulates extensively in adipose tissue

Correct Answer: Chlorthiazide is shorter-acting and often requires more frequent dosing than chlorthalidone

Q28. Which symptom should prompt immediate evaluation for severe hyponatremia in a patient on chlorthiazide?

• Mild headache lasting a day
• Confusion, seizures, or marked lethargy
• Increased appetite
• Painless ankle swelling

Correct Answer: Confusion, seizures, or marked lethargy

Q29. Which of the following best explains why thiazides are less effective in patients with advanced renal failure?

• They require active tubular secretion into the proximal tubule to reach their site of action, which is reduced at low GFR
• They are degraded by renal enzymes that are increased in renal failure
• They are transformed into inactive metabolites in uremia
• They cause immediate hyperfiltration and worsen renal failure

Correct Answer: They require active tubular secretion into the proximal tubule to reach their site of action, which is reduced at low GFR

Q30. Which clinical monitoring schedule is most appropriate after initiating chlorthiazide therapy?

• No monitoring is needed for the first year
• Check blood pressure, serum electrolytes (Na+, K+, Ca2+), and renal function within 1–2 weeks and periodically thereafter
• Only monitor liver enzymes weekly
• Only monitor uric acid annually

Correct Answer: Check blood pressure, serum electrolytes (Na+, K+, Ca2+), and renal function within 1–2 weeks and periodically thereafter

Download