Diuretics Flashcards
What are the functions of the kidney?
Regulatory
Excretory
Endocrine
Metabolism
What drugs act on the renal tubules?
Carbonic anhydrase inhibitors Osmotic diuretics Loop diuretics Thiazides K+ sparing diuretics Aldosterone antagonists ADH antagonists
Where do carbonic anhydrase inhibitors work?
PCT
How do carbonic anhydrase inhibitors work?
Prevent reuptake of sodium bicarb and water
What are carbonic anhydrase inhibitors generally used to treat?
Glaucoma
What are the carbonic anhydrase inhibitors?
Acetazolamide and dorzolamide
What are the ADRs associated with carbonic anhydrase inhibitors?
Metabolic acidosis and hypokalaemia
Name an osmotic diuretic.
Mannitol
Where do osmotic diuretics work?
The PCT and descending loop of Henle
What are the ADRs associated with osmotic diuretics?
Excessive water loss and hypernatraemia
Where do loop diuretics work?
Thick ascending loop of Henle
Name some loop diuretics.
Furosemide
Bumetamide
How do loop diuretics work?
Inhibit NaCl reabsorption - very potent as major site of water reabsorption
What are the ADRs associated with loop diuretics?
Hypokalaemia
Concurrent Ca2+ and Mg2+ excretion
What are examples of thiazide diuretics?
Metolazone
Indapamide
Others ending in -thiazide
Where do thiazide diuretics work?
DCT
How do thiazide diuretics work?
Inhibit NaCl reabsorption and promotes Ca2+ reabsorption
What are the ADRs associated with thiazide diuretics?
Hypokalaemia
Hyperuricaemia
Hypercalcaemia
Where do aldosterone antagonists work?
Collecting ducts
Name the aldosterone antagonists.
Spironalactone
Eplerenone
What is good about aldosterone antagonists?
There are K+ sparing
How do ADH antagonists work?
(Aside from the obvious) Reduce the ability of the collecting ducts to concentrate urine.
Name some ADH antagonists.
Lithium
Demeclocycline
Name 2 other drugs with diuretic activity.
Digoxin
Amiloride
How is digoxin diuretic in nature?
Inhibits tubular Na+K+ ATPase
How is amiloride diuretic in nature?
Inhibits Na+ channels in DCT and CD. K+ sparing, so good adjunct
What general ADRs should we be aware of for diuretics?
Anaphylaxis/rash (rare) Hypovolaemia and hypotension Acute renal failure (due to above) Electrolyte disturbance Metabolic disturbance
What are the common ADRs specific to thiazides?
Gout
Erectile dysfunction
What are the ADRs specific to furosemide?
Ototoxicity (rare)
What is the ADR specific to bumetanide?
Myalgia
What are the common ADRs specific to spironolactone?
Hyperkalaemia
Painful gynaecomastia
Which diuretics interact with ACE inhibitors, and how?
K+ sparing diuretics to cause hyperkalaemia -> cardiac problems
Which diuretics interact with aminoglycosides (e.g. gentamicin), and how?
Loop diuretics to cause ototoxicity and nephrotoxicity
Can digoxin be added onto a thiazide and a loop diuretic?
No as Loop + thiazide can cause hypokalaemia which can precipitate digoxin toxicity
What group of drug increases the risk of hypokalaemia when taken alongside thiazides or loop diuretics?
Steroids
What happens if i mix a beta blocker and a thiazide?
Hyperglycaemia
Hyperlipidaemia
Gout (via hyperuricaemia)
Thiazide + what = increased risk of hyponatraemia?
Carbamazepine
Can diuretic resistance occur?
Yes
How can diuretic resistance occur iatrogenically?
Incomplete treatment of the primary disorder
NSAIDs
Volume depletion
How can diuretic resistance occur due to patient factors?
Continued high dietary Na+ intake
Poor compliance
Volume depletion
What are the 3 major indications for diuretic use?
Heart Failure
Hypertension
Decompensated Liver Disease
Which diuretics do we use for heart failure?
Loop and thiazides
Spironalactone (not for diuretic effect)
Which diuretics do we use for hypertension?
Thiazides
Spironalactone
Loop
Which diuretics do we use for decompensated liver disease?
Spironolactone for managing oedema
Loop diuretics
How do we prescribe in renal failure?
Avoid nephrotoxins as much as possible.
Decrease dosage in line with eGFR if metabolised by or excreted via the kidneys.
What is more likely to occur in renal failure?
Hyperkalaemia
Describe the identification and management of hyperkalaemia.
Bloods and ECG to diagnose
Treat with calcium gluconate, insulin (+dextrose), calcium resonium, sodium bicarb, and salbutamol.
Identify the cause and treat
How does hyperkalaemia show on an ECG?
Tall tented T waves (V4-V6)
Fewer P waves
Widened QRS complexes
