Diuretics — Sites & Mechanisms

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

2007B Q02

Exam question

Outline the sites and mechanisms of action of diuretics. Give one example of drug acting at each site and list two side effects for each drug.

CICMWrecks answer

Master answer

Location	Drug	Mechanism of Action	Adverse Effects
PCT	Acetazolamide	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 Renal stones Hyponatraemia
LoH	Frusemide	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 Hyponatraemia Hypokalaemia Hypomagnesaemia
DCT	Thiazide	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
CD	Spironolactone	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	Gynaecomastia Hyperkalaemia Renal stones
Other	Mannitol	Increases osmolality of of luminal fluid → decreases osmotic gradient for H₂O reabsorption	Hypotension Tachycardia Thrombophlebitis Convulsions

CICMWrecks 2019

1 appearance

Exam	Exact exam wording	Candidate success
2007B Q02	Outline the sites and mechanisms of action of diuretics. Give one example of drug acting at each site and list two side effects for each drug.	57%