6) Diuretics Flashcards
Describe the mechanism of action of Carbonic Anhydrase inhibitors
Works at the PCT
> Prevent re absorption of Na+ with bicarbonate
What ADRs can occur with Carbonic Anhydrase Inhibitors ?
> Because of reduced bicarbonate re absorption, patients will become Acidotic
Hypokalaemia, increase ENac activity => K+ loss at CD
When are Carbonic Anhydrase Inhibitors used ?
It is used to treat Glaucoma
Describe the mechanism of action of Osmotic Agents e.g. Mannitol
They ensure that water remains in the Lumen of the tubule.
> Works at the PCT
What ADRs can occur with Osmotic Agent ?
> Reduced Intracellular volume
> Risk of Hypernatraemia
When are Osmotic Agents used ?
Swellings in the brain
What is the mechanism of action of Loop Diuretics?
> Example
Blocks NKCC2 in the Loop of Henle, this leads to an increase in Na+ and thus water excretion
> Furosemide
What ADRs can occur with Loop Diuretics ?
> Hypocalcaemia, > Ototoxicity > Alkalosis > Hypokalaemia > Increased LDL > Gout
Describe the mechanism of action of Thiazides
Blocks NCCT channel in the DCT inhibiting NaCl re absorption
What ADRs can occur with Thiazides
> Gout > Hyperglycaemia > Increased LDL > Hypercalcaemia > HypoKalaemia
Describe the mechanism of action of Amiloride ?
Blocks ENaC in the collecting duct
> It is a potassium sparing diuretic
Describe the mechanism of action of Spironolactone ?
Acts as a Aldosterone Antagonist.
> Potassium Sparing Diuretic
What are some ADRs of Spironolactone ?
> Hyperkalaemia
Impotence
Painful Gynaecomastia
What is the mechanism of action ADH Antagonists (Aquaretics)
> Example ?
> Inhibits the action of ADH
Causes diuresis but not natriuresis
Tolvaptan
Lithium
When may ADH Antagonists be used ?
> APCKD
> Patient has Hyponatraemia
Name two other substances which have diuretic action ?
> Alcohol , prevents ADH release
>Caffeine, increased GFR and reduced Na re absorption
List General Adverse Drug Reactions of Diuretics
> Anaphylaxis > Hypovolaemia > Hypo tension => Leading to AKI and RAAS activation > Electrolyte Imbalance > Metabolic Abnormalities e..g Acidosis > Be careful when co prescribing with other drugs such as ACEi, Digoxin, B-Blockers and Steroids
What Patient factors may lead to Diuretic Resistance
> Gut Oedema e.g. in Nephrotic Syndrome this means that the drug cannot be absorbed and thus may need to be given IV
> Heart Failure - Blood isn’t pumped adequately to the kidney so the drug isn’t delivered there, thus may need to increase
> Liver Problems - Certain drugs such as furosemide rely on albumin for distribution
> Kidney Problems
> Salt intake
What diuretic do you use to treat Hypertension ?
> Thiazides - Act as Vasodilators as well
Spironolactone (loop diuretic)
- Choose if cause is Primary Hyperaldosteronism
What diuretic do you use to treat Heart Failure ?
> Loop diuretics - does not affect BP
What diuretic do you use to treat Liver Disease ?
> Spironolactone
> Loop Diuretics
What diuretic do you use to treat Nephrotic Syndrome ?
> Loop Diuretic High Dose
> + Thiazide if no improvements
