Adverse Effects and Drug Interactions — MCQs

10 questions

Hypercalcemia is caused by all except:

Which of the following agents requires the MOST caution when combined with spironolactone due to increased risk of hyperkalemia:

A patient on lithium therapy developed hypertension and was started on a thiazide diuretic. After a few days, he developed coarse tremors and other symptoms suggestive of lithium toxicity. What is the probable mechanism of interaction between thiazide diuretics and lithium?

Loop and thiazide diuretics commonly cause clinically significant loss of:

Side effects of thiazide diuretics include all of the following except?

Long-term use of which diuretic agent can result in gynaecomastia?

All of the following drugs are known to worsen hyperkalemia except

All the following adverse effects can be caused by Loop Diuretics EXCEPT -

Hand foot syndrome is an adverse effect of what?

Q10

A 28-year-old woman with a history of seizures is prescribed a classic anticonvulsant that primarily works by inhibiting voltage-gated sodium channels. Which drug is most likely being prescribed?

Adverse Effects and Drug Interactions Indian Medical PG Practice Questions and MCQs

Question 1: Hypercalcemia is caused by all except:

A. Lithium
B. Loop diuretics (Correct Answer)
C. Thiazides
D. Vitamin D intoxication

Explanation: Hypercalcemia is caused by all except: ***Loop diuretics*** - **Loop diuretics** promote the urinary excretion of calcium by inhibiting the reabsorption of calcium in the thick ascending limb of the loop of Henle [3]. - This effect leads to a **decrease** in serum calcium levels and thus do not cause hypercalcemia. [3] *Lithium* - **Lithium** can cause hypercalcemia by increasing the set point for calcium sensing in the parathyroid glands, leading to increased parathyroid hormone (PTH) secretion. - This results in a mild, chronic hypercalcemia, often in the context of **secondary hyperparathyroidism**. *Vitamin D intoxication* - **Vitamin D intoxication** leads to excessive absorption of calcium from the gut and increased bone resorption, both contributing to hypercalcemia [1]. - High levels of vitamin D cause hypercalcemia that **suppresses PTH secretion** through negative feedback, resulting in hypercalcemia with inappropriately low PTH levels. *Thiazides* - **Thiazide diuretics** can cause mild hypercalcemia by increasing renal tubular reabsorption of calcium [2]. - They enhance calcium reabsorption in the **distal convoluted tubule**, leading to a slight elevation in serum calcium [2], [3].

Question 2: Which of the following agents requires the MOST caution when combined with spironolactone due to increased risk of hyperkalemia:

A. ACE inhibitors (Correct Answer)
B. Beta-blockers
C. Amlodipine
D. Chlorothiazide

Explanation: ***ACE inhibitors*** - Spironolactone is a **potassium-sparing diuretic** that increases potassium levels by blocking aldosterone's effects in the collecting duct [1]. - **ACE inhibitors** also decrease aldosterone production [2], leading to reduced potassium excretion and a significant risk of **severe hyperkalemia** when combined with spironolactone [1, 2].*Beta-blockers* - While beta-blockers can cause a slight increase in plasma potassium by inhibiting cellular potassium uptake, this effect is generally modest and does not pose a major hyperkalemia risk when co-administered with spironolactone. - Their primary interaction concerns blood pressure and heart rate, not direct potassium handling.*Amlodipine* - Amlodipine is a **calcium channel blocker** that primarily causes vasodilation and does not significantly alter potassium balance. - Therefore, it does not substantially increase the risk of hyperkalemia when used concurrently with spironolactone.*Chlorothiazide* - Chlorothiazide is a **thiazide diuretic** that promotes potassium excretion, leading to a risk of hypokalemia. - When combined with spironolactone, a potassium-sparing diuretic, these agents can **partially offset each other's effects** on potassium balance, potentially reducing the risk of hyperkalemia compared to ACE inhibitors.

Question 3: A patient on lithium therapy developed hypertension and was started on a thiazide diuretic. After a few days, he developed coarse tremors and other symptoms suggestive of lithium toxicity. What is the probable mechanism of interaction between thiazide diuretics and lithium?

A. Thiazide increases the tubular reabsorption of lithium (Correct Answer)
B. Thiazide inhibits the metabolism of lithium
C. Thiazides act as an add-on drug to lithium
D. None of the above

Explanation: ***Thiazide increases the tubular reabsorption of lithium*** - Thiazide diuretics cause a decrease in sodium reabsorption in the distal convoluted tubule, leading to increased sodium excretion in urine. - The kidneys, in an attempt to conserve sodium, increase reabsorption in the proximal tubule. Because **lithium** is reabsorbed similarly to sodium in the proximal tubule, this increased reabsorption also affects lithium, leading to a rise in its plasma concentration and toxicity. *Thiazide inhibits the metabolism of lithium* - Lithium is primarily excreted by the kidneys and is not significantly metabolized in the body. - Thiazide diuretics do not affect enzyme systems responsible for drug metabolism. *Thiazides act as an add on the drug to lithium* - This statement is vague and does not explain a mechanism of interaction leading to toxicity. - While both drugs might be prescribed concurrently for different conditions, "add on" does not describe a pharmacological interaction causing altered drug levels. *None of the above* - This option is incorrect because a clear and well-understood mechanism for the interaction between thiazide diuretics and lithium exists.

Question 4: Loop and thiazide diuretics commonly cause clinically significant loss of:

A. Sodium
B. Calcium
C. Potassium (Correct Answer)
D. Iron

Explanation: ***Potassium*** - Loop diuretics (e.g., furosemide) and thiazide diuretics (e.g., hydrochlorothiazide) inhibit sodium reabsorption in the renal tubules, leading to **increased urinary potassium excretion**. - This results in **hypokalemia**, a clinically significant side effect that requires monitoring and often necessitates **potassium supplementation** or the addition of **potassium-sparing diuretics** (e.g., spironolactone, amiloride). - Hypokalemia can cause muscle weakness, cardiac arrhythmias, and increased digitalis toxicity. *Sodium* - While diuretics do increase sodium excretion (their primary therapeutic mechanism), the question focuses on **clinically significant electrolyte loss** that requires intervention. - Sodium loss is the intended therapeutic effect for volume reduction, not typically considered a problematic "side effect." *Calcium* - **Loop diuretics** increase calcium excretion (useful in hypercalcemia treatment). - **Thiazide diuretics** actually decrease calcium excretion (can increase serum calcium, useful in osteoporosis). - The effects are variable depending on diuretic class. *Iron* - Diuretics do not directly affect iron excretion or absorption. - Iron balance is regulated primarily through intestinal absorption, not renal excretion.

Question 5: Side effects of thiazide diuretics include all of the following except?

A. Hypokalemia
B. Erectile dysfunction
C. Hyponatremia
D. Hypocalcemia (Correct Answer)

Explanation: ***Hypocalcemia*** - Thiazide diuretics are known to cause **hypercalcemia** (increased calcium reabsorption), NOT hypocalcemia, due to their action on the distal convoluted tubule. - This property makes them useful in treating conditions like **idiopathic hypercalciuria** and **calcium-containing kidney stones**. - The mechanism involves enhanced passive calcium reabsorption in the proximal tubule and active reabsorption in the distal tubule. *Hyponatremia* - Thiazide diuretics impair the kidney's ability to dilute urine and reabsorb sodium in the distal tubule, leading to **increased sodium excretion** and potential hyponatremia. - This effect is more pronounced in **elderly patients** and those with increased free water intake. - Hyponatremia is one of the most common electrolyte disturbances with thiazides. *Hypokalemia* - Thiazides increase the delivery of sodium and water to the collecting duct, leading to increased activity of the **renin-angiotensin-aldosterone system** and enhanced potassium secretion. - This results in **potassium wasting** and hypokalemia, which may require potassium supplementation or combination with potassium-sparing diuretics. *Erectile dysfunction* - Thiazide diuretics can cause **erectile dysfunction** through mechanisms including effects on vascular smooth muscle, reduced blood flow, and possible hormonal effects. - This is a common side effect reported in male patients using these medications for hypertension and may affect compliance.

Question 6: Long-term use of which diuretic agent can result in gynaecomastia?

A. Amiloride
B. Acetazolamide
C. Spironolactone (Correct Answer)
D. Triamterene

Explanation: ***Spironolactone*** - **Spironolactone** is an **aldosterone antagonist** with a chemical structure similar to steroid hormones, enabling it to also act as a weak **androgen receptor antagonist** and **progesterone receptor partial agonist**. - This anti-androgenic and progestogenic activity can lead to **gynaecomastia** (breast enlargement in males), **breast tenderness**, and menstrual irregularities as dose-dependent side effects. *Amiloride* - **Amiloride** is a **potassium-sparing diuretic** that directly blocks epithelial sodium channels (ENaC) in the collecting duct. - It does not interfere with hormone receptors and is **not associated with gynaecomastia**. *Acetazolamide* - **Acetazolamide** is a **carbonic anhydrase inhibitor** that primarily acts in the proximal tubule. - Its mechanism of action does not involve modulation of steroid hormones, and it is **not known to cause gynaecomastia**. *Triamterene* - **Triamterene** is another **potassium-sparing diuretic** that, like amiloride, directly blocks ENaC channels. - It lacks significant hormonal effects and is **not associated with gynaecomastia**.

Question 7: All of the following drugs are known to worsen hyperkalemia except

A. Furosemide (Correct Answer)
B. ACE inhibitors
C. Amiloride
D. Spironolactone

Explanation: ***Furosemide*** - **Furosemide** is a loop diuretic that acts on the **thick ascending limb of the loop of Henle**, inhibiting the reabsorption of sodium, chloride, and potassium. - This action leads to increased excretion of potassium in the urine, thus **preventing hyperkalemia** and often causing hypokalemia. *ACE inhibitors* - **ACE inhibitors** block the production of angiotensin II, leading to decreased aldosterone secretion. - Reduced aldosterone levels decrease potassium excretion in the renal tubules, which can **worsen hyperkalemia**. *Amiloride* - **Amiloride** is a potassium-sparing diuretic that blocks sodium channels in the collecting duct. - This action reduces potassium secretion, making it a drug that can **worsen hyperkalemia**. *Spironolactone* - **Spironolactone** is an aldosterone antagonist that also acts as a potassium-sparing diuretic. - By blocking aldosterone's effects, it **decreases potassium excretion** in the renal tubules and can therefore worsen hyperkalemia.

Question 8: All the following adverse effects can be caused by Loop Diuretics EXCEPT -

A. Hypomagnesemia
B. Hypercalcemia (Correct Answer)
C. Hyperuricemia
D. Hyperglycemia

Explanation: ***Hypercalcemia*** - Loop diuretics inhibit the reabsorption of calcium in the thick ascending limb of the loop of Henle, leading to **increased urinary calcium excretion** and, consequently, **hypocalcemia** [2], [3]. - Therefore, loop diuretics actively decrease calcium levels, so hypercalcemia is not an adverse effect. *Hypomagnesemia* - Loop diuretics interfere with magnesium reabsorption in the thick ascending limb, which can lead to **increased urinary excretion of magnesium** and subsequently cause **hypomagnesemia** [1], [2]. - This effect is clinically significant as it can exacerbate other electrolyte imbalances or cause symptoms like muscle weakness or arrhythmias. *Hyperuricemia* - Loop diuretics can lead to **hyperuricemia** by competing with uric acid for secretion into the renal tubule and by increasing its reabsorption, thereby decreasing its excretion [1]. - This can precipitate or worsen gout, especially in susceptible individuals [1]. *Hyperglycemia* - Loop diuretics, like thiazide diuretics, can cause **hyperglycemia** by impairing insulin secretion and increasing peripheral insulin resistance. - This effect is more pronounced with higher doses and prolonged use, potentially worsening glycemic control in diabetic patients or unmasking latent diabetes.

Question 9: Hand foot syndrome is an adverse effect of what?

A. Bleomycin
B. Etoposide
C. Actinomycin D
D. 5-Fluorouracil (Correct Answer)

Explanation: ***5-Fluorouracil*** - **Hand-foot syndrome** (**palmar-plantar erythrodysesthesia**) is a common and dose-limiting side effect of 5-Fluorouracil and its prodrug, capecitabine. - It presents with **redness**, **swelling**, **pain**, and **desquamation** of the palms and soles. *Bleomycin* - The primary dose-limiting toxicity of bleomycin is **pulmonary fibrosis**, not hand-foot syndrome. - Other common toxicities include **hyperpigmentation** of the skin and mucocutaneous reactions, but not typically severe palmar-plantar changes. *Etoposide* - Etoposide is associated with adverse effects like **myelosuppression** (leukopenia, thrombocytopenia) and **alopecia**. - While skin reactions can occur, **hand-foot syndrome** is not a characteristic or common side effect of etoposide. *Actinomycin D* - Actinomycin D (dactinomycin) is known for causing **myelosuppression**, **nausea**, **vomiting**, and **mucositis**. - It can also cause **radiation recall phenomenon**, but not typically hand-foot syndrome as a primary or common adverse effect.

Question 10: A 28-year-old woman with a history of seizures is prescribed a classic anticonvulsant that primarily works by inhibiting voltage-gated sodium channels. Which drug is most likely being prescribed?

A. Valproate
B. Carbamazepine
C. Lamotrigine
D. Phenytoin (Correct Answer)

Explanation: ***Phenytoin*** - **Phenytoin** is the **classic prototype anticonvulsant** [1] that primarily works by **blocking voltage-gated sodium channels**, thus stabilizing the neuronal membrane and preventing repetitive firing [2]. - It is effective in treating various seizure types, including **focal** and **generalized tonic-clonic seizures** [1]. - As the traditional first-line agent in this class, it is the most likely answer when referring to a "classic" sodium channel blocker [1]. *Carbamazepine* - While **carbamazepine** also works by **blocking voltage-gated sodium channels** [2], it is structurally related to tricyclic antidepressants and came after phenytoin. - It's often used for **focal seizures** and **trigeminal neuralgia**. - Considered an important alternative but not the "classic" prototype [1]. *Valproate* - **Valproate** has **multiple mechanisms of action**, including inhibiting **GABA transaminase** (increasing GABA levels), blocking **sodium channels**, and modulating **T-type calcium channels** [2]. - Its broad spectrum is useful for both **focal** and **generalized seizures**, including absence seizures. - Not primarily classified as a sodium channel blocker due to its multiple mechanisms. *Lamotrigine* - **Lamotrigine** is a **newer anticonvulsant** [1] that inhibits presynaptic **voltage-gated sodium channels**, reducing the release of excitatory neurotransmitters like glutamate [2]. - It is effective against various seizure types, including **focal**, **generalized tonic-clonic**, and seizures associated with **Lennox-Gastaut syndrome**. - Developed later as a second-generation antiepileptic drug [1].

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