diuretics Flashcards
what are the classes of diuretics?
carbonic anhydrase inhibitors loop thiazide potassium sparing osmotic
name carbonic anhydrase inhibitors
acetazolamide
what is the definition of a diuretic?
stops sodium from being reabsorbed
what part of the kidneys do carbonic anhydrase inhibitors work on?
PCT
what is the net effect of carbonic anhydrase in the PCT?
allows bicarbonate to be pumped out into the blood and Na+ to be reabsorbed into the PCT from the urine
what is the mode of action of CA inhibitors?
block CA so they stop the dissociation of H2CO3 in the urine so CO2 isnt absorbed into the PCT
- Stops Na+ from being reabsorbed by inhibiting the absorption of bicarbonate
what is acetazolamide used for?
glaucoma
epilepsy
mountain sickness
why is acetazolamide used in acute mountain sickness?
- respiratory alkalosis occurs as you ascend bc PaO2 decreases so minute ventilation increases to compensate
- acetozolamide creates metabolic acidosis to compensate for the respiratory alkalosis
- stops cerebral and pulmonary oedema
what are the side effects of carbonic anhydrase inhibitors?
Metabolic acidosis
Sedation
Sulphonamide antibiotics
Bone marrow suppression
what are the contraindications of CA inhibitors?
Contra indicated in significant CKD
name loop diuretics
frusemide
bumetanide
what part of the kidneys do loop diuretics act on?
thick ascending limb of the loop of henle
act on the Na/K/Cl cotransporter
what is the mode of action of loop diuretics?”
blocks the action of the Na/K/Cl transporter so Na+, K+ and Cl- are all excreted
also leads to more magnesium and calcium in the urine –> hypocalcaemia and hypomagnesium
what is the most potent diuretic?
loop diuretics
what do loop diuretics cause the excretion of?
potassium sodium water calcium magnesium
what are the indications of loop diuretics?
Hypertension
Heart failure
Volume overload from CKD
what are the side effects of loop diuretics?
hypokalaemia
dehydration –> acute kidney failure
kidney stones (bc of the high levels of calcium in the urine)
deafness (at high doses)
name thiazide diuretics
Bendroflumethiazide Hydrochlorothiazide Thiazide like drugs: Chlorthalidone Indapamide Metolazone
what part of the kidneys do thiazide diuretics act on?
distal convoluted tubule
Na/Cl cotransporter
what do thiazide diuretics lead to the excretion of?
Na
Cl
water
what do thiazide diuretics lead to the reabsorption of?
calcium
high levels of blood calcium and low levels of urine calcium
what are the clinical uses of thiazide diuretics?
Primarily an antihypertensive
Reduction in plasma volume
Reduction in peripheral resistance (causes slight vasodilation)
what are the side effects of thiazide diuretics?
Electrolyte effects:
Hypokalaemia
Hypercalcaemia
Hyponatraemia (particularly in old people)
Hyperglycaemia
Hypercholesterolaemia
what are the groups of potassium sparing diuretics and name examples of each
- Epithelial Na Channel antagonists: Amiloride and Triamterene
- Aldosterone antagonists: Spironolactone and Eplerenone
what are the targets of potassium sparing diuretics?
collecting tubule
what is the mode of action of potassium sparing diuretics like amiloride?
Blocks sodium channels (ENaC)
Prevents sodium reabsorption
Don’t prevent K+ secretion so no hypokalaemia bc less K+ and H+ are being exchanged for the Na+
what are the clinical uses of amiloride?
Heart failure Hypokalaemia (from other diuretics) Co-amilofruse Co-amilozide Cirrhosis
what are the side effects of amiloride?
hyperkalaemia
hyponatremia
what is the mode of action of spironolactone?
Aldosterone receptor antagonist
Competitively binds receptors at the aldosterone-dependent sodium-potassium exchange site in the collecting tubule
what are the uses of aldosterone inhibitors?
hyperaldosteronism (Conns)
heart failure
Hypokalaemia
Cirrhosis
what are the side effects of aldosterone inhibitors?
hyperkalaemia!!
gynecomastia
hyponatraemia (Cirrhosis)
what is the most important clinical osmotic diuretic?
mannitol
what are osmotic diuretics?
Any osmotically active molecule that is freely filtered in the glomerulus, and is not reabsorbed by the tubules
what is the mechanism of action of osmotic diuretics?
Osmotically active molecule in the tubular lumen: stops water absorption
Reduces reabsorption of all solutes:
Sodium, potassium, urea…
Molecule ‘drags’ sodium from interstitial space
what are the clinical indications of osmotic diuretics?
cerebral oedema
oliguric acute renal failure
what are the side effects of osmotic diuresis?
- Transient fluid overload - Pulmonary odema
- Other non pharmacological osmotic diuretics: Glucose, DKA/HHS,
Urea - Disequilibrium syndrome
when do you not use diuretics?
When hypotensive When dehydrated When hypokalaemic (Loop/Thiazide) When hyperkalaemic (Amiloride, aldosterone antagonists) Post surgery, with a poor urine output
