Diuretics And Drugs In Kidney Failure Flashcards
What are the functions of the kidney?
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)
Give some generic diuretic ADRs
Increased urinary frequency
Hypovolaemia and hypotension leading to AKI
Electrolyte disturbance
Metabolic abnormalities
Increased urinary frequency
What are the specific ADRs for thiazides diuretics?
Gout, erectile dysfunction
What are the specific ADRs for furosemide?
Ototoxic
What are the specific ADRs for spironolactone?
Hyperkalaemia, painful gynaecomastia
What is the main DDI affecting spironolactone?
ACE inhibitors can increase the risk of hyperkalaemia and induce cardiac problems
What are the main DDIs for loop diuretics?
Aminoglycosides - Ototoxic and nephrotoxic
Digoxin - increased risk of hypokalaemia and increased digoxin binding and toxicity
Steroids - increased risk of hypokalaemia
What are the main DDIs for thiazides?
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
Give some reasons why there may be resistance to diuretics
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
What are the main indications for diuretics?
Heart failure, hypertension, decompensated liver failure. conn’s syndrome
What drugs would you use to treat heart failure?
Loop diuretic
Spironolactone
Thiazide if required
ACE inhibitor
B-blocker
What drugs would you use to treat hypertension?
> 55 - Ca2+ blocker/thiazide +/- ACE inhibitor
<55 - ACE inhibitor
B-blocker, loop diuretic, spironolactone (if uncontrolled)
What drugs would you use to treat compensated liver failure?
Spironolactone
Loop diuretic
What drug would you use to treat Conn’s syndrome?
Aldosterone antagonist
Name some nephrotoxic drugs
ACE inhibitors, aminoglycosides, cyclosporin A, metformin, NSAIDs
Why can ACE inhibitors be nephrotoxic?
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
Why are NSAIDs nephrotoxic?
They reduce renal blood flow
What should you consider when prescribing in renal failure?
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)
Why is renal function over-estimated in the elderly?
Creatine is dependent on body mass (less muscle mass)
What should you consider when prescribing in the elderly?
That renal function is likely to be overestimated
Start low
Titrate
Consider polypharmacy
What would you see on an ECG of hyperkalaemia?
Peaked T waves, widening of the QRS complex
How would you treat hyperkalaemia?
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
