Diuretics And Drugs In Kidney Failure

Question 1

What are the functions of the kidney?

Answer 1

Regulatory - fluid balance, acid-base balance, electrolyte balance

Excretory - waste products, drug elimination

Endocrine - renin-angiotensin-aldosterone, erythropoietin, prostaglandins

Metabolism - vitamin D, polypeptides (insulin, PTH)

Question 2

Give some generic diuretic ADRs

Answer 2

Increased urinary frequency

Hypovolaemia and hypotension leading to AKI

Electrolyte disturbance

Metabolic abnormalities

Increased urinary frequency

Question 3

What are the specific ADRs for thiazides diuretics?

Answer 3

Gout, erectile dysfunction

Question 4

What are the specific ADRs for furosemide?

Answer 4

Ototoxic

Question 5

What are the specific ADRs for spironolactone?

Answer 5

Hyperkalaemia, painful gynaecomastia

Question 6

What is the main DDI affecting spironolactone?

Answer 6

ACE inhibitors can increase the risk of hyperkalaemia and induce cardiac problems

Question 7

What are the main DDIs for loop diuretics?

Answer 7

Aminoglycosides - Ototoxic and nephrotoxic

Digoxin - increased risk of hypokalaemia and increased digoxin binding and toxicity

Steroids - increased risk of hypokalaemia

Question 8

What are the main DDIs for thiazides?

Answer 8

Digoxin - increases risk of hypokalaemia and increases digoxin binding and toxicity

Steroids - increases risk of hypokalaemia

B-blockers - hyperglycaemia, hyperlipidaemia, hyperuricaemia

Carbamazepine - increased risk of hyponatraemia

Question 9

Give some reasons why there may be resistance to diuretics

Answer 9

Incomplete treatment of underlying disorder

High intake of Na+

Non-compliance

Poor absorption

Volume depletion - reducing filtration of diuretics, increasing aldosterone thus Na+ reabsorption

Reduced renal blood flow e.g. NSAIDs

Question 10

What are the main indications for diuretics?

Answer 10

Heart failure, hypertension, decompensated liver failure. conn’s syndrome

Question 11

What drugs would you use to treat heart failure?

Answer 11

Loop diuretic

Spironolactone

Thiazide if required

ACE inhibitor

B-blocker

Question 12

What drugs would you use to treat hypertension?

Answer 12

> 55 - Ca2+ blocker/thiazide +/- ACE inhibitor

<55 - ACE inhibitor

B-blocker, loop diuretic, spironolactone (if uncontrolled)

Question 13

What drugs would you use to treat compensated liver failure?

Answer 13

Spironolactone

Loop diuretic

Question 14

What drug would you use to treat Conn’s syndrome?

Answer 14

Aldosterone antagonist

Question 15

Name some nephrotoxic drugs

Answer 15

ACE inhibitors, aminoglycosides, cyclosporin A, metformin, NSAIDs

Question 16

Why can ACE inhibitors be nephrotoxic?

Answer 16

In renal artery stenosis glomerular filtration pressure is reduced which would normally activate RAAS to dilate the afferent arteriole and constrict the efferent arteriole to increase the pressure. However the ACE inhibitor preferentially dilates the efferent arteriole which reduces the pressure further

Question 17

Why are NSAIDs nephrotoxic?

Answer 17

They reduce renal blood flow

Question 18

What should you consider when prescribing in renal failure?

Answer 18

Avoid nephrotoxic drugs

Reduce doses in line with GFR if metabolism/excretion is by kidneys

Monitor renal function and drug levels

(Know that hyperkalaemia is more likely and uraemic patients are more likely to bleed)

Question 19

Why is renal function over-estimated in the elderly?

Answer 19

Creatine is dependent on body mass (less muscle mass)

Question 20

What should you consider when prescribing in the elderly?

Answer 20

That renal function is likely to be overestimated

Start low

Titrate

Consider polypharmacy

Question 21

What would you see on an ECG of hyperkalaemia?

Answer 21

Peaked T waves, widening of the QRS complex

Question 22

How would you treat hyperkalaemia?

Answer 22

Calcium glauconate - reduces risk of ventricular fibrillation

Insulin/dextrose - encourages cells to take up insulin thus K+

Sodium bicarbonate - to increase pH shifting K+ from extracellular to intracellular

Salbutamol - protest cellular uptake of K+

Calcium resonium - binds to K+ forming s complex than can not be absorbed from the GI system