Past Papers · SAQ

Diuretics — Classes & Effects

Current · V5 (2025) → E3.i Historical · V4 (2023) → H3.i 1 exam appearance

2022B Q17

Exam question

Describe the site of action, mechanism of action and the biochemical effects of five different classes of diuretics; include an example in each class.

CICMWrecks answer

Master answer

Sites and Mechanisms of actions of diuretics

ClassDrugSitesMechanism of ActionBiochemical effects
Carbonic Anhydrase InhibitorAcetazolamidePCTPrevents 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
LoopFrusemideLoHInhibits 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
ThiazideHydrochlorothiazideDCTInhibits 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 AntagonistSpironolactoneCDPrevents 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
OsmoticMannitolOtherIncreases osmolality of luminal fluid
→ decreases osmotic gradient for H2O reabsorption		Hypokalemia
Hyponatremia
Hypocalcemia

CICMWrecks 2019

Further Reading:

Click to Open CICMWrecks Table: Diuretics

Past papers

Exam appearances

1 appearance
Exam Exact exam wording Candidate 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. 90%