Digitoxin MCQs With Answer

Digitoxin MCQs With Answer

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Introduction:

Digitoxin MCQs With Answer provides B. Pharm students a focused, exam-oriented review of this classic cardiac glycoside. This concise set emphasizes digitoxin’s pharmacology, mechanism of action, pharmacokinetics, therapeutic uses, adverse effects, drug interactions, monitoring and toxicity management. Questions explore hepatic metabolism, high protein binding, long elimination half-life, clinical indications in heart failure and atrial arrhythmias, electrolyte influences, ECG changes and antidotal therapy — equipping students to apply principles in clinical pharmacy and therapeutics. Each MCQ reinforces critical concepts and decision-making skills essential for safe drug use and counselling. ‘Now let’s test your knowledge with 30 MCQs on this topic.’

Q1. Which is the primary mechanism of action of digitoxin?

  • Competitive blockade of beta-1 adrenergic receptors
  • Inhibition of Na+/K+-ATPase leading to increased intracellular calcium
  • Activation of phosphodiesterase III increasing cAMP
  • Blockade of L-type calcium channels in myocardium

Correct Answer: Inhibition of Na+/K+-ATPase leading to increased intracellular calcium

Q2. Compared with digoxin, digitoxin is:

  • More water-soluble and renally excreted
  • Less lipophilic with shorter half-life
  • More lipophilic with longer half-life
  • Exclusively metabolized by kidneys

Correct Answer: More lipophilic with longer half-life

Q3. The major route of elimination for digitoxin is:

  • Renal excretion of unchanged drug
  • Hepatic metabolism and biliary excretion
  • Exhalation via lungs
  • Glomerular filtration followed by tubular secretion

Correct Answer: Hepatic metabolism and biliary excretion

Q4. Which electrolyte disturbance most commonly predisposes a patient to digitoxin toxicity?

  • Hypernatremia
  • Hypokalemia
  • Hypermagnesemia
  • Hyponatremia

Correct Answer: Hypokalemia

Q5. Digitoxin’s protein binding is generally:

  • Negligible (<10%)
  • Moderate (30–50%)
  • High (around 90% or more)
  • Variable but always <25%

Correct Answer: High (around 90% or more)

Q6. Which clinical indication is digitoxin primarily used for?

  • Acute myocardial infarction reperfusion therapy
  • Rate control in chronic atrial fibrillation and symptomatic heart failure
  • First-line therapy for ventricular fibrillation
  • Treatment of essential hypertension

Correct Answer: Rate control in chronic atrial fibrillation and symptomatic heart failure

Q7. The typical ECG change associated with digitalis effect includes:

  • Shortened PR interval and peaked T waves
  • Prolonged QT interval with U waves
  • PR interval prolongation and characteristic ST-segment scooping
  • Widened QRS with delta waves

Correct Answer: PR interval prolongation and characteristic ST-segment scooping

Q8. Which drug interaction is likely to increase serum digitoxin concentration?

  • Rifampicin (hepatic enzyme inducer)
  • Phenobarbital (enzyme inducer)
  • Quinidine (reduces clearance and displaces from tissues)
  • St. John’s wort (induces metabolism)

Correct Answer: Quinidine (reduces clearance and displaces from tissues)

Q9. Which of the following best explains why digitoxin dosing must be cautious in elderly patients?

  • Elderly have increased renal clearance causing subtherapeutic levels
  • Higher muscle mass increases distribution volume dramatically
  • Altered hepatic function, reduced clearance, high tissue accumulation and drug interactions
  • They are resistant to digitalis effects and require larger doses

Correct Answer: Altered hepatic function, reduced clearance, high tissue accumulation and drug interactions

Q10. Which monitoring is most important during digitoxin therapy?

  • Serum albumin only
  • Serum electrolytes (K+, Mg2+, Ca2+) and periodic drug levels
  • Complete blood count daily
  • Serum bilirubin every 4 hours

Correct Answer: Serum electrolytes (K+, Mg2+, Ca2+) and periodic drug levels

Q11. In acute digitoxin overdose, which of the following is a key early management step if ingestion was recent?

  • Immediate haemodialysis
  • Administration of activated charcoal to reduce absorption
  • High-dose intravenous potassium without monitoring
  • Oral cholestyramine to increase absorption

Correct Answer: Administration of activated charcoal to reduce absorption

Q12. Which statement about digitoxin pharmacokinetics is correct?

  • It is primarily excreted unchanged by kidneys and unaffected by liver disease
  • Extensive enterohepatic circulation contributes to prolonged action
  • It is rapidly eliminated within hours requiring frequent dosing
  • It undergoes no hepatic metabolism

Correct Answer: Extensive enterohepatic circulation contributes to prolonged action

Q13. Which adverse effect is classically associated with cardiac glycoside toxicity?

  • Blue-gray skin hyperpigmentation
  • Gingival hyperplasia
  • Nausea, vomiting, visual disturbances (yellow-green halos) and arrhythmias
  • Ototoxicity with permanent hearing loss

Correct Answer: Nausea, vomiting, visual disturbances (yellow-green halos) and arrhythmias

Q14. Why is digitoxin less affected than digoxin by renal impairment?

  • It is mostly metabolized and eliminated via the liver and bile
  • It relies exclusively on glomerular filtration
  • It is not absorbed from the GI tract in renal patients
  • It is inactivated by kidneys to non-toxic metabolites

Correct Answer: It is mostly metabolized and eliminated via the liver and bile

Q15. Which of the following drugs can reduce digitoxin plasma levels by inducing hepatic metabolism?

  • Verapamil
  • Phenytoin
  • Amiodarone
  • Spironolactone

Correct Answer: Phenytoin

Q16. Which clinical sign would most strongly suggest acute severe digitoxin toxicity?

  • Bradyarrhythmia progressing to ventricular fibrillation with hyperkalemia
  • Isolated mild hypertension without symptoms
  • Isolated ankle edema only at night
  • Chronic mild cough without cardiac symptoms

Correct Answer: Bradyarrhythmia progressing to ventricular fibrillation with hyperkalemia

Q17. Therapeutic drug monitoring for digitoxin is useful because:

  • Serum levels closely correlate with toxicity and efficacy and metabolism varies between patients
  • Levels never change with drug interactions
  • It has an extremely short half-life making levels irrelevant
  • It is exclusively dialyzable so levels are constant

Correct Answer: Serum levels closely correlate with toxicity and efficacy and metabolism varies between patients

Q18. Which condition increases sensitivity to digitoxin’s effects?

  • Hyperkalemia from renal failure
  • Atrial fibrillation in a young healthy adult without electrolyte disturbances
  • Hypothyroidism and advanced age
  • Hyperthyroidism

Correct Answer: Hypothyroidism and advanced age

Q19. Which statement about drug interactions with digitoxin is correct?

  • Loop diuretics decrease toxicity by raising potassium levels
  • Calcium supplements and hypercalcemia reduce risk of arrhythmias
  • Concurrent use of potassium-wasting diuretics may increase risk of toxicity
  • All antibiotics uniformly reduce digitoxin levels

Correct Answer: Concurrent use of potassium-wasting diuretics may increase risk of toxicity

Q20. When converting a patient from digoxin to digitoxin, which pharmacokinetic factor is most important?

  • Short renal half-life of digitoxin
  • Digitoxin’s long half-life and hepatic clearance necessitate dose adjustments and monitoring
  • Digitoxin has no tissue binding so immediate switch is safe without monitoring
  • Both drugs are identical in dosing and monitoring

Correct Answer: Digitoxin’s long half-life and hepatic clearance necessitate dose adjustments and monitoring

Q21. Which laboratory abnormality can be a marker of severe acute cardiac glycoside poisoning?

  • Marked hypokalemia only
  • Marked hyperkalemia due to inhibition of Na+/K+-ATPase
  • Severe leukocytosis
  • Profound hypocalcemia always

Correct Answer: Marked hyperkalemia due to inhibition of Na+/K+-ATPase

Q22. Which of the following is a recommended specific therapy for life-threatening digitoxin poisoning?

  • Digoxin-specific antibody fragments (Digibind/DigiFab)
  • Prolonged intravenous calcium infusion as sole therapy
  • High-dose vitamin K
  • Immediate oral flumazenil

Correct Answer: Digoxin-specific antibody fragments (Digibind/DigiFab)

Q23. Which statement about oral absorption of digitoxin is true?

  • Oral bioavailability is poor and unpredictable, so IV is preferred
  • It is well absorbed orally and suitable for maintenance therapy
  • It cannot be given orally due to complete first-pass metabolism
  • Absorption is only via rectal route

Correct Answer: It is well absorbed orally and suitable for maintenance therapy

Q24. Which symptom is more characteristic of chronic digitalis toxicity than acute toxicity?

  • Severe hyperkalemia with sudden collapse
  • Gradual onset of anorexia, nausea, fatigue, and visual changes
  • Immediate loss of consciousness within minutes
  • Profound hypothermia

Correct Answer: Gradual onset of anorexia, nausea, fatigue, and visual changes

Q25. Which pharmacologic effect on the heart is produced by therapeutic doses of digitoxin?

  • Increased AV nodal conduction leading to tachycardia
  • Decreased AV nodal conduction and positive inotropy
  • Negative inotropic and decreased cardiac output
  • Complete blockade of ventricular pacemaker activity

Correct Answer: Decreased AV nodal conduction and positive inotropy

Q26. Which patient factor would most likely reduce digitoxin clearance and require dose reduction?

  • Young adult with normal liver function
  • Severe hepatic impairment
  • Hyperthyroidism increasing metabolic rate
  • Concurrent therapy with hepatic enzyme inducers

Correct Answer: Severe hepatic impairment

Q27. Which of the following antibiotics can increase digitoxin levels by decreasing intestinal flora that metabolize the drug?

  • Rifampicin
  • Clarithromycin
  • Digoxin-specific Fab
  • Metronidazole

Correct Answer: Clarithromycin

Q28. Which monitoring parameter best predicts risk of arrhythmia in a patient on digitoxin?

  • Serial blood glucose
  • Serum potassium concentration
  • Serum cholesterol
  • White blood cell count

Correct Answer: Serum potassium concentration

Q29. Why may digoxin-specific Fab be less effective for digitoxin poisoning than for digoxin poisoning?

  • Digitoxin does not bind to Na+/K+-ATPase
  • Antibody affinity for digitoxin is lower and enterohepatic recycling complicates removal
  • Digitoxin is water-soluble and rapidly dialyzed
  • Antibodies enhance digitoxin activity

Correct Answer: Antibody affinity for digitoxin is lower and enterohepatic recycling complicates removal

Q30. Which counseling point is important for patients on long-term digitoxin therapy?

  • Avoid routine monitoring; symptoms are the only guide
  • Report symptoms like nausea, visual changes, palpitations, and avoid over-the-counter drugs without consulting clinician
  • Stop potassium supplements and diuretics immediately
  • Increase intake of high-fiber laxatives to enhance absorption

Correct Answer: Report symptoms like nausea, visual changes, palpitations, and avoid over-the-counter drugs without consulting clinician

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