9. Diuretics PHARM Flashcards
what are some causes of edema?
heart failure, hepatic cirrhosis, renal disease, sympathetic activation, hypoalbuminemia
how does sympathetic activation contribute to edema?
contributes to Na retention, vasoconstriction of the efferent arteriole (same as AtII). also, renin release via B1 receptor
how are diuretics delivered to their site of activity? three methods
- glomerular filtration of drugs –> tubule
- prox tubule secretion by carriers
- reabsorption by diffusion
why do diuretics that work more proximally have a higher max capacity?
more Na is absorbed proximally than distally
Example of an osmotic diuretic? how does it work?
Mannitol.
filtered, but not reabsorbed. reduces tonicity of the renal medulla, decreases water reabsorption
what are OATs?
organic anion transporter proteins. can carry drugs from blood into the prox tubule
Mannitol: mechanism?
can pull water out of cells, into vasculature, and then diurese through kidney. contrast with albumin, which can maintain vasculature volume but cannot cause osmotic diuresis (too big to filter, stays in serum)
mannitol: therapeutic uses?
glaucoma, cerebral edema
carbonic anhydrase inhibitors: example medication?
acetazolamide
CA inhibitor: location of action? mechanism?
prox tubule. block bicarb reabsorption, reduce Na reabsorption as a result. increase urinary excr of bicarb, Na
CA inhibitors: why limited use/short term effect?
they cause metabolic acidosis (due to bicarb loss). once you have lost enough bicarb, they are less effective
Ca inh: how do they cause hypokalemia?
at collecting duct, Na is reabsorbed in exchange for K – since there is more Na present, more is reabsorbed here and more K is wasted. Increased urinary K secretion/excretion.
CA inhibitors: side effects?
hypoK
calcium stones due to alkalization of urine
hypersensitivity reactions due to sulfonamide residue
Thiazide: mechanism of action
- inhibits NaCl symporter in distal convoluted tubule
- increases Na/Cl excretion
- blocks urinary diluting capacity
- some degree of carbonic anhydrase inhibition
Thiazide: name of drug?
hydrochlorothiazide
Thiazide: side effects? how does it cause these?
hypokalemia, hyponatremia
prevents reabsorption of Na at the Na/Cl symporter, so more Na arrives at the collecting duct. More is reabsorbed there so K is wasted. But overall more Na is excreted than usual.
Hypersensitivity reactions: not sure how, but know it anyway.
Thiazide: impact on calcium?
can cause hyperCa. because less Na reabsorbed at distal tubule, so Ca is reab in order to maintain electroneutral cytosol
Therapeutic uses for thiazides
hypertension, increasing bone density in elderly women, edema, calcium stones
loop diuretic: prototypical drug?
furosemide
loop diuretic: mechanism?
blocks Na-K-Cl symporter in ascending LOH
increases Na/Cl excretion
increases K excretion
what effect do loop diuretics have on Ca and Mg excretion?
increase excretion of Ca, Mg due to decreased paracellular absorption in ascending limb