Pharmacology Flashcards
Example of loop diuretics
Furosemide
Action of loop diuretics
Inhibits Na+K+Cl- cotransporter -> increase ions in the tubules -> reduce hyperosmolarity in intersitium -> reduce in water reabsorption
What must happen for loop diuretics to work
Loop diuretics must be filtered out of the glomerulus into the ascending loop of Henle to work
= patients with poor renal function will need higher dose for sufficient effect
Where does loop diuretics act on
Ascending limb of loop of Henle
Which NKCC variant does loop diuretics mainly act on
NKCC2
When is loop diuretics indicated
Heart failure
Resistant hypertension in those with poor renal function
Side effects of loop diuretics
Hyponatraemia
Hypokalaemia
Ototoxicity
Hypocalcaemia
Hypomagnesaemia
Gout
loop diuretics can interact with other drugs to cause adverse effects. Which drugs
Steroids -> further decrease K+ level
Aminoglycosides -> increase risk of ototoxicity
NSAID -> decrease effect of loop diuretics
Examples of thiazide diuretics
Indapamide
Chlortalidone
Hydrochlorothiazide
Action of thiazide diuretics
Inhibit Na+ Cl- symporter
Where does thiazide diuretics act on
Distal convoluted tubule
Effect of thiazide diuretics
- Decrease in Na+ reabsorption = more excretion of water
- Decrease in Na+ causes increase in Na+ Ca2+ anti porter activity (Ca2+ in Na+ out)-> increase Ca2+ into blood
- Potassium loss
- Loss of Cl-
Why does thiazide diuretics cause loss of potassium
Because less Na+ is absorbed, the body will try to compensate by increasing aldosterone secretion.
Aldosterone increases Na+ reabsorption in exchange for K+ excretion
Hence more K+ excreted
Loss of Cl- due to thiazide diuretics causes
Hypochloraemic metabolic alkalosis
Side effects of thiazide diuretics
Postural hypotension
Impaired glucose tolerance
Impotence
Hyponatraemia
Hypokalaemia
Hypercalcaemia
Gout
Why can thiazide diuretics be used to prevent recurrence of renal stones
Because it causes hypercalcaemia = hypocalciuria (more Ca2+ in blood)
Thiazide diuretics is contraindicated in
renal failure
may worsen glycaemic control in diabetics
Lithium therapy
Types of potassium sparing diuretics
Aldosterone antagonist
ENaC (epithelial Na+ channels) inhibitors
Example of aldosterone antagonist
Spironolactone
Eplerenone
Examples of ENaC inhibitors
Amiloride
Triamterene
Aldosterone antagonists act on
Collecting duct - blocks expression of Na+/K+ ATPase (used by aldosterone to increase sodium reabsorption and K+ excretion)
ENaC inhibitors act on
DCT
Potassium sparing diuretics are contraindicated in
Addison’s disease
ACEi use
Why is potassium sparing diuretics contraindicated in ACEi use
ACEi blocks aldosterone hence further decrease K+ secretion which can cause hypokalaemia