Diuretics

Question 1

MOA of osmotic diuretics

Answer 1

increase RBF, alter medullary tonicity so that tubular water reabsorption is osmotically blocked

Question 2

Uses of osmotic diuretics (mannitol)?

Answer 2

localised oedema, glaucoma

Question 3

ADRs of osmotic diuretics?

Answer 3

GI upset, injection site reactions, chills/fever, acute renal failure, CNS toxicity

Question 4

MOA of CA inhibitors?

Answer 4

inhibit recycling of H+ secretion and Na+ reabsorption

Question 5

Uses of CA inhibitors?

Answer 5

localised oedema e.g. glaucoma

Question 6

MOA of loop/high ceiling diuretics?

Answer 6

acts at thick ascending limb, blocks Na+/K+/2Cl- symporter, block 15-25% of Na+ reabsorption

Question 7

ADRs of loop diuretics

Answer 7

K+ wasting (dysrhythmias, ECG changes, increased digoxin toxicity, muscle weakness, constipation, drowsiness, irritability, confusion, dizziness), Na+ Mg2+ Ca2+ loss, impaired uric acid excretion, dose-related hearing loss

Question 8

Uses of loop diuretics

Answer 8

APO, CHF, liver cirrhosis, renal failure, hypertension, in drug overdose, in combination with thiazides or K-sparing diuretics

Question 9

MOA of thiazide and related diuretics?

Answer 9

increased Na+ excretion 5-10%, increased K+ excretion, decreased Ca2+ excretion

Question 10

ADRs of thiazides and related diuretics?

Answer 10

hypokalaemia, hyperuricaemia, hypomagnesaemia, hypercholesterolaemia, hyperglycaemia, acid-base imbalance, erectile dysfunction, digoxin toxicity increased

Question 11

K+ sparing diuretic drug groups?

Answer 11

aldosterone antagonists and Na+ channel blockers, act on late distal tubule and collecting ducts

Question 12

MOA of aldosterone antagonists (spironolactone)

Answer 12

inhibit 3Na+/2K+ exchanger on basolateral membrane and luminal membrane Na+ channel

Question 13

uses of aldosterone antagonists (like spironolactone)

Answer 13

with thiazides and loop diuretics to produce diuresis without hypokalaemia, used in conditions associated with hyperaldosteronism/Cushing’s, improves survival in CHF

Question 14

MOA of Na+ channel blockers (amiloride)

Answer 14

blocks Na+ channel on luminal membrane

Question 15

Uses of Na+ channel blockers (amiloride)

Answer 15

to spare K+ in the absence of aldosterone, used with thiazide and loop diuretics

Question 16

What are some drug interactions with K+ sparing drugs leading to hyperkalaemia?

Answer 16

• other K+ sparing diuretics
• K+ supplements
• ACE inhibitors
• AT1 receptor antagonists