Pharmacology

Question 1

Example of loop diuretics

Answer 1

Furosemide

Question 2

Action of loop diuretics

Answer 2

Inhibits Na+K+Cl- cotransporter -> increase ions in the tubules -> reduce hyperosmolarity in intersitium -> reduce in water reabsorption

Question 3

What must happen for loop diuretics to work

Answer 3

Loop diuretics must be filtered out of the glomerulus into the ascending loop of Henle to work

= patients with poor renal function will need higher dose for sufficient effect

Question 4

Where does loop diuretics act on

Answer 4

Ascending limb of loop of Henle

Question 5

Which NKCC variant does loop diuretics mainly act on

Answer 5

NKCC2

Question 6

When is loop diuretics indicated

Answer 6

Heart failure
Resistant hypertension in those with poor renal function

Question 7

Side effects of loop diuretics

Answer 7

Hyponatraemia
Hypokalaemia
Ototoxicity
Hypocalcaemia
Hypomagnesaemia
Gout

Question 8

loop diuretics can interact with other drugs to cause adverse effects. Which drugs

Answer 8

Steroids -> further decrease K+ level

Aminoglycosides -> increase risk of ototoxicity

NSAID -> decrease effect of loop diuretics

Question 9

Examples of thiazide diuretics

Answer 9

Indapamide
Chlortalidone
Hydrochlorothiazide

Question 10

Action of thiazide diuretics

Answer 10

Inhibit Na+ Cl- symporter

Question 11

Where does thiazide diuretics act on

Answer 11

Distal convoluted tubule

Question 12

Effect of thiazide diuretics

Answer 12

1. Decrease in Na+ reabsorption = more excretion of water
2. Decrease in Na+ causes increase in Na+ Ca2+ anti porter activity (Ca2+ in Na+ out)-> increase Ca2+ into blood
3. Potassium loss
4. Loss of Cl-

Question 13

Why does thiazide diuretics cause loss of potassium

Answer 13

Because less Na+ is absorbed, the body will try to compensate by increasing aldosterone secretion.
Aldosterone increases Na+ reabsorption in exchange for K+ excretion

Hence more K+ excreted

Question 14

Loss of Cl- due to thiazide diuretics causes

Answer 14

Hypochloraemic metabolic alkalosis

Question 15

Side effects of thiazide diuretics

Answer 15

Postural hypotension
Impaired glucose tolerance
Impotence
Hyponatraemia
Hypokalaemia
Hypercalcaemia
Gout

Question 16

Why can thiazide diuretics be used to prevent recurrence of renal stones

Answer 16

Because it causes hypercalcaemia = hypocalciuria (more Ca2+ in blood)

Question 17

Thiazide diuretics is contraindicated in

Answer 17

renal failure
may worsen glycaemic control in diabetics
Lithium therapy

Question 18

Types of potassium sparing diuretics

Answer 18

Aldosterone antagonist
ENaC (epithelial Na+ channels) inhibitors

Question 19

Example of aldosterone antagonist

Answer 19

Spironolactone
Eplerenone

Question 20

Examples of ENaC inhibitors

Answer 20

Amiloride
Triamterene

Question 21

Aldosterone antagonists act on

Answer 21

Collecting duct - blocks expression of Na+/K+ ATPase (used by aldosterone to increase sodium reabsorption and K+ excretion)

Question 22

ENaC inhibitors act on

Answer 22

DCT

Question 23

Potassium sparing diuretics are contraindicated in

Answer 23

Addison’s disease
ACEi use

Question 24

Why is potassium sparing diuretics contraindicated in ACEi use

Answer 24

ACEi blocks aldosterone hence further decrease K+ secretion which can cause hypokalaemia

Question 25

Examples of osmotic diuretics

Answer 25

Mannitol Isosorbide Glycerine

Question 26

Where do osmotic diuretics act on

Answer 26

PCT Loop of Henle Collecting duct

Question 27

Side effects of osmotic diuretics

Answer 27

Cardiovascular toxicity immediately after injection

Question 28

Osmotic diuretic is contraindicated in

Answer 28

Heart failure

Question 29

Examples of carbonic anhydrase inhibitors

Answer 29

Acetazolamide Dorzolamide

Question 30

Action of carbonic anhydrase inhibitors

Answer 30

Acts on proximal tubules to inhibit bicarbonate reabsorption

Question 31

Effect of carbonic anhydrase inhibitors

Answer 31

Reduces H2CO3 dissociating into HCO3- and H+ -> reduces Na+ reabsorption (because H+ was supposed to be excreted in exchange for reabsorption of Na+)

Question 32

Side effects of carbonic anhydrase inhibitors

Answer 32

Metabolic acidosis (H2CO3 is for acid base balance) Renal stones

Question 33

Which drugs can interact with digoxin to cause toxicity

Answer 33

Loop and thiazide diuretics Spironolactone Amiodarone Verapamil Dilitiazem

Question 34

What happens in digoxin toxicity

Answer 34

Caused by hypokalaemia Digoxin usually competes with K+ to bind to a transporter Hypokalaemia = less competition = enhanced effect of digoxin

Question 35

Symptoms of digoxin toxicity

Answer 35

Unwell Yellow-green vision Anorexia Arrhythmia - bradycardia / heart block Confusion

Question 36

Management of digoxin toxicity

Answer 36

Digibind