Furosemide is a commonly used diuretic agent.

What is the mode of action of this drug?

Options:
explanation: This is the correct answer. Loop diuretics such as furosemide and bumetanide inhibit the sodium-potassium-chloride (Na-K-Cl) cotransporters, also known as NKCC, which are found in the thick ascending limb of the loop of Henle. This reduces the absorption of sodium, potassium and chloride ions, as well as water alongside sodium. As a result, urine output increases and subsequently, blood pressure decreases. Side effects include hypotension, electrolyte disturbances (hyponatremia, hypokalaemia, etc.), ototoxicity and gout.
name: NKCC2 (Na-K-Cl co-transporters) antagonist
label: a
answer: yes
explanation: This is not the correct answer. Thiazide diuretics such as bendroflumethiazide and indapamide block the sodium-chloride symporter in the distal convoluted tubule, preventing the reabsorption of sodium and chloride ions. Water is excreted alongside sodium ions and this results in increased urine output and subsequent reduced blood pressure. On the other hand, furosemide is a loop diuretic that inhibits the sodium-potassium-chloride (Na-K-Cl) cotransporters, also known as NKCC, found in the thick ascending limb of the loop of Henle.
name: Sodium-chloride symporter antagonist
label: c
answer: no
explanation: This is not the correct answer. Mineralocorticoid antagonists such as spironolactone and eplerenone bind to mineralocorticoid receptors in the renal tubule cells, leading to increased sodium excretion and potassium reabsorption in the distal tubule and collecting duct. Water is excreted alongside sodium ions and this results in increased urine output and subsequent reduced blood pressure. On the other hand, furosemide is a loop diuretic that inhibits the sodium-potassium-chloride (Na-K-Cl) cotransporters, also known as NKCC, found in the thick ascending limb of the loop of Henle.
name: Mineralocorticoid receptor antagonist
label: b
answer: no
explanation: This is not the correct answer. angiotensin-II receptor blockers such as candesartan, irbesartan and losartan block angiotensin-II receptors in smooth muscle cells in vessels, adrenal gland cortical cells and adrenergic nerve synapses. This results in vasodilation, decreased secretion of vasopressin and decreased production of aldosterone respectively, leading to reduced blood pressure.
name: angiotensin-II receptor antagonist
label: e
answer: no
explanation: This is not the correct answer. Carbonic anhydrase inhibitors such as acetazolamide prevent the reabsorption of bicarbonate, which requires this enzyme to be reabsorbed in the proximal convoluted tubule. This results in bicarbonate and associated sodium and water loss, enabling this drug to act as a weak diuretic. The bicarbonate loss also results in metabolic acidosis, thus useful in altitude sickness as it stimulates compensatory hyperventilation (increased respiratory depth and frequency), allowing better acclimatisation to low oxygen environments. On the other hand, furosemide is a loop diuretic that inhibits the sodium-potassium-chloride (Na-K-Cl) cotransporters, also known as NKCC, found in the thick ascending limb of the loop of Henle.
name: Carbonic anhydrase inhibitor
label: d
answer: no

Correct answer: a