Isosorbide dinitrate MCQs With Answer

Isosorbide dinitrate MCQs With Answer

Isosorbide dinitrate (ISDN) is an organic nitrate widely covered in B. Pharm curricula for its pharmacology, therapeutic uses and clinical implications. This introduction and question set focus on mechanism of action (NO-mediated guanylate cyclase activation and increased cGMP), pharmacokinetics (oral vs sublingual absorption, hepatic denitration to isosorbide mononitrate), clinical indications (angina, heart failure adjunct), adverse effects (headache, hypotension, reflex tachycardia), tolerance development and important drug interactions (notably PDE5 inhibitors). The MCQs emphasize dosing principles, formulation differences, monitoring and patient counseling to build deeper understanding for exam and practice. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which of the following best describes the primary mechanism of action of isosorbide dinitrate?

• Inhibition of angiotensin-converting enzyme to reduce afterload
• Direct blockade of L-type calcium channels to decrease myocardial contractility
• Release of nitric oxide leading to activation of guanylate cyclase and increased cGMP
• Beta-adrenergic receptor antagonism to lower heart rate

Correct Answer: Release of nitric oxide leading to activation of guanylate cyclase and increased cGMP

Q2. Isosorbide dinitrate produces symptomatic relief in angina primarily by:

• Increasing coronary vascular resistance
• Reducing myocardial oxygen demand via venodilation and decreased preload
• Increasing cardiac afterload to improve coronary perfusion
• Stimulating myocardial contractility to enhance output

Correct Answer: Reducing myocardial oxygen demand via venodilation and decreased preload

Q3. Which statement about oral isosorbide dinitrate pharmacokinetics is correct?

• It has negligible first-pass hepatic metabolism and very high bioavailability
• It undergoes hepatic denitration to active metabolites such as isosorbide mononitrate
• It is eliminated primarily unchanged by the kidneys without metabolism
• It is converted to nitroglycerin as its main metabolite

Correct Answer: It undergoes hepatic denitration to active metabolites such as isosorbide mononitrate

Q4. Development of nitrate tolerance during continuous ISDN therapy is primarily due to:

• Upregulation of guanylate cyclase activity
• Depletion of intracellular thiol groups required for bioactivation
• Accumulation of nitrate in adipose tissue
• Enhanced renal excretion of cGMP

Correct Answer: Depletion of intracellular thiol groups required for bioactivation

Q5. Which clinical advice is most appropriate when a patient uses sublingual isosorbide dinitrate for acute angina?

• Swallow the tablet immediately for faster effect
• Lie down or sit before taking the dose to reduce risk of syncope
• Take with a high-fat meal to improve absorption
• Avoid contacting the tablet with saliva to prevent irritation

Correct Answer: Lie down or sit before taking the dose to reduce risk of syncope

Q6. The most common adverse effect reported with isosorbide dinitrate therapy is:

• Chronic cough
• Headache due to cerebral vasodilation
• Hyperkalemia
• Dry mouth

Correct Answer: Headache due to cerebral vasodilation

Q7. Which drug interaction with isosorbide dinitrate is considered potentially life-threatening and must be avoided?

• Concurrent use of selective serotonin reuptake inhibitors (SSRIs)
• Concurrent use of phosphodiesterase-5 inhibitors (e.g., sildenafil)
• Concurrent use of H2 receptor antagonists
• Concurrent use of calcium carbonate antacid

Correct Answer: Concurrent use of phosphodiesterase-5 inhibitors (e.g., sildenafil)

Q8. Which formulation characteristic makes isosorbide mononitrate preferable to isosorbide dinitrate for once-daily dosing in some patients?

• ISMN undergoes extensive first-pass metabolism producing active metabolites
• ISMN has more predictable oral bioavailability and longer duration of action
• ISMN is only available as an intravenous preparation
• ISMN causes no tolerance on chronic use

Correct Answer: ISMN has more predictable oral bioavailability and longer duration of action

Q9. Which physiologic effect is most pronounced with organic nitrates like ISDN?

• Arteriolar vasodilation causing major decrease in afterload
• Primarily venodilation causing decreased preload
• Direct positive inotropic effect on myocardium
• Significant bronchoconstriction

Correct Answer: Primarily venodilation causing decreased preload

Q10. In which clinical situation are nitrates relatively contraindicated due to risk of severe hypotension?

• Right ventricular infarction
• Stable exertional angina without hypotension
• Peripheral arterial disease without coronary disease
• Hyperthyroidism-related palpitations

Correct Answer: Right ventricular infarction

Q11. The bioactivation of isosorbide dinitrate to release nitric oxide is enhanced by which cellular factor?

• High extracellular calcium concentration
• Reduced intracellular thiol groups (e.g., glutathione)
• Elevated cyclic AMP levels
• Activation of monoamine oxidase

Correct Answer: Reduced intracellular thiol groups (e.g., glutathione)

Q12. Which monitoring parameter is most relevant when initiating or uptitrating ISDN therapy?

• Serum creatinine only
• Blood pressure and symptoms of orthostatic hypotension
• Serum potassium routinely
• Daily blood glucose

Correct Answer: Blood pressure and symptoms of orthostatic hypotension

Q13. Combining hydralazine with isosorbide dinitrate in heart failure is beneficial because:

• Both drugs are nitrates that increase preload synergistically
• Hydralazine reduces afterload while ISDN reduces preload, improving hemodynamics
• Hydralazine prevents nitrate tolerance by blocking metabolism
• Both drugs block beta-receptors to reduce heart rate

Correct Answer: Hydralazine reduces afterload while ISDN reduces preload, improving hemodynamics

Q14. A pharmacist counseling a patient starting ISDN should advise which dosing strategy to reduce tolerance?

• Use continuous infusion without interruption for maximal effect
• Use a scheduled nitrate-free interval each day (e.g., overnight)
• Double the dose if effects wane over time without consultation
• Take with grapefruit juice to increase plasma levels

Correct Answer: Use a scheduled nitrate-free interval each day (e.g., overnight)

Q15. Which metabolic fate is characteristic of isosorbide dinitrate in the liver?

• Conversion to isosorbide mononitrate is a major metabolic pathway
• Extensive glucuronidation to inactive conjugates only
• Oxidation to nitrobenzene derivatives
• Excretion unchanged in bile primarily

Correct Answer: Conversion to isosorbide mononitrate is a major metabolic pathway

Q16. Which patient education point is essential for those prescribed ISDN tablets?

• Store in the refrigerator at all times
• Keep an extra dose in a sealed bottle for sublingual use if angina occurs
• Take daily with a high-calorie snack to avoid nausea
• Avoid sudden standing after dose due to risk of dizziness

Correct Answer: Avoid sudden standing after dose due to risk of dizziness

Q17. Which effect would you expect when ISDN is administered in combination with alcohol?

• Alcohol antagonizes nitrate action, reducing efficacy
• Combined use can increase hypotensive effects and dizziness
• Alcohol prevents nitrate tolerance development
• There is no interaction; effects are independent

Correct Answer: Combined use can increase hypotensive effects and dizziness

Q18. Which statement about sublingual administration of isosorbide dinitrate is true?

• Sublingual ISDN avoids first-pass metabolism and provides rapid onset
• Sublingual route prolongs duration compared to oral sustained release
• Sublingual tablets should be swallowed immediately for effect
• Sublingual administration is associated with more systemic toxicity than IV

Correct Answer: Sublingual ISDN avoids first-pass metabolism and provides rapid onset

Q19. Which adverse cardiovascular reflex is commonly seen after nitrate-induced vasodilation?

• Bradycardia due to direct sinus node suppression
• Reflex tachycardia due to baroreceptor-mediated sympathetic activation
• Heart block due to AV nodal depression
• Coronary vasospasm due to alpha-adrenergic activation

Correct Answer: Reflex tachycardia due to baroreceptor-mediated sympathetic activation

Q20. In which form is isosorbide dinitrate commonly available for acute angina relief?

• Topical ointment only
• Sublingual tablet or spray for rapid onset
• Depot intramuscular injection for immediate effect
• Transdermal patch exclusively for acute attacks

Correct Answer: Sublingual tablet or spray for rapid onset

Q21. Which laboratory abnormality is most directly associated with organic nitrate overdose?

• Marked hyperglycemia
• Severe methemoglobinemia requiring methylene blue
• Profound hypotension and lactic acidosis from tissue hypoperfusion
• Acute increase in transaminases

Correct Answer: Profound hypotension and lactic acidosis from tissue hypoperfusion

Q22. Which population requires special caution or dose adjustment when prescribing ISDN?

• Patients with severe hypotension or volume depletion
• Patients with stable blood pressure and renal impairment only
• Young healthy adults with no comorbidities
• Patients using topical emollients regularly

Correct Answer: Patients with severe hypotension or volume depletion

Q23. Which statement correctly compares isosorbide dinitrate (ISDN) and nitroglycerin (NTG)?

• ISDN is always faster acting than NTG when given sublingually
• NTG has a shorter duration of action and faster onset than oral ISDN
• NTG is inactive until converted to ISDN in vivo
• ISDN is only used intravenously while NTG is oral

Correct Answer: NTG has a shorter duration of action and faster onset than oral ISDN

Q24. Which sign suggests a patient may be developing significant nitrate tolerance?

• Increased frequency of angina episodes despite regular dosing
• Marked decrease in headache frequency and increased efficacy
• Improved exercise tolerance over weeks of therapy
• Stable blood pressure with consistent symptom control

Correct Answer: Increased frequency of angina episodes despite regular dosing

Q25. Which mechanism explains why nitrates relieve pulmonary congestion in acute decompensated heart failure?

• Direct diuretic effect on renal tubules
• Venodilation reduces venous return and pulmonary capillary pressure
• Blockade of aldosterone receptors
• Increase in myocardial contractility to clear pulmonary fluid

Correct Answer: Venodilation reduces venous return and pulmonary capillary pressure

Q26. Which counseling point is appropriate for storage of sublingual ISDN tablets or spray?

• Keep spray exposed to light to maintain potency
• Store in the original container at room temperature away from moisture
• Refrigerate after opening to prolong shelf life
• Remove tablets from blister and carry loose in pocket for convenience

Correct Answer: Store in the original container at room temperature away from moisture

Q27. Which enzyme system is primarily responsible for hepatic denitration of ISDN?

• CYP450-mediated oxidative denitration producing active mononitrates
• Monoamine oxidase converting to inactive amines
• Acetylcholinesterase hydrolysis
• Renal dehydrogenases in proximal tubule

Correct Answer: CYP450-mediated oxidative denitration producing active mononitrates

Q28. For exam preparation, which pharmacodynamic property of ISDN is most important to remember?

• It selectively increases systemic vascular resistance
• Its main effect is venodilation leading to reduced preload and myocardial oxygen demand
• It primarily blocks sodium channels in cardiac tissue
• It produces long-term beta-adrenergic blockade

Correct Answer: Its main effect is venodilation leading to reduced preload and myocardial oxygen demand

Q29. Which adverse effect requires immediate medical attention and possible discontinuation of ISDN?

• Mild transient headache after the first dose
• Severe symptomatic hypotension with syncope
• Occasional flushing lasting minutes
• Transient dizziness that resolves when seated

Correct Answer: Severe symptomatic hypotension with syncope

Q30. In pharmacology exams, which statement about nitrate tolerance reversal strategies is correct?

• Increasing daily dose continuously prevents tolerance
• Implementing a daily nitrate-free interval and using lowest effective dose help reverse or prevent tolerance
• Combining with PDE5 inhibitors reverses tolerance
• Tolerance cannot be prevented or modified by dosing changes

Correct Answer: Implementing a daily nitrate-free interval and using lowest effective dose help reverse or prevent tolerance

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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