Canonical Question

Renal Pharm – Diuretics

V5 E3.i Historical V4 H3.i 1 appearance

Master answer

Sites and Mechanisms of actions of diuretics

Class	Drug	Sites	Mechanism of Action	Biochemical effects
Carbonic Anhydrase Inhibitor	Acetazolamide	PCT	Prevents the intracellular conversion of CO₂ and H₂O to H₂CO₃ → Resulting HCO₃ usually reabsorbed via Na/HCO₃ co transporter therefore decreased HCO₃ leads to decreased Na reabsorption → decreased reabsorption of water	Metabolic acidosis Hyponatraemia Hypokalemia Hyperchloremia
Loop	Frusemide	LoH	Inhibits Na/K/2Cl transporter on luminal membrane preventing ion reabsorption → increases osmolality of luminal fluid → decreased osmotic gradient for water reabsorption	Hypochloraemic metabolic alkalosis Hypernatraemia Hypokalaemia Hypomagnesaemia Hypophosphatemia Acidification of urine
Thiazide	Hydrochlorothiazide	DCT	Inhibits Na/Cl transporter on the luminal membrane preventing Na and Cl reabsorption → increases osmolality in luminal fluid → decreased osmotic gradient for water reabsorption	Hypochloraemic metabolic alkalosis Hyponatraemia Hypokalaemia Dyslipidaemia Hyperglycaemia
Aldosterone Antagonist	Spironolactone	CD	Prevents activity of aldosterone → Decreased ENaC channels for Na reabsorption in the collecting duct and decreased Na/K ATPase activity in collecting duct → Prevents Na reabsorption and consequently reduced osmosis	Hyponatremia Hyperkalaemia Metabolic acidosis
Osmotic	Mannitol	Other	Increases osmolality of luminal fluid → decreases osmotic gradient for H₂O reabsorption	Hypokalemia Hyponatremia Hypocalcemia

CICMWrecks 2019

Further Reading:

Click to Open CICMWrecks Table: Diuretics

Exam appearances

Exam	Exact wording	Relationship	Success
2022B Q17	Describe the site of action, mechanism of action and the biochemical effects of five different classes of diuretics; include an example in each class.	historical_member	90.00%