Exam 4: Diuretics Flashcards
Prototype thiazide diuretic:
Hydrochlorothiazide
Site of action of thiazides:
Distal convoluted tubule
MoA of thiazides:
Impairs Na+/Cl+ reabsorption, drawing water into the filtrate to be excreted
Precaution with thiazides:
K+ depleting
HTN mechanism of thiazides:
Peripheral vasodilation
Anesthesia concerns with thiazides:
Electrolytes: hypokalemia, hypochloremia, hypomagnesemia Muscle weakness that potentiates NMBs Nephropathy Increased risk of dig toxicity Fluid volume depletion
Dose effects of thiazides:
Increased dose has little extra effect
Prototype loop diuretic:
Furosemide
Site of action of loop diuretics:
Thick ascending loop of Henle
MoA of furosemide:
Inhibit the passive transport of K+/Na+/Cl- from the lumen, keeping them + water in the filtrate
PK of furosemide:
Onset: 2 - 10min (IV)
Extensively protein bound
Renal secretion!
Indications for furosemide:
Mobilization of edema
Reduction of ICP
Hypercalcemia
Differential dx of oliguria
Dosage of furosemide:
0.1 - 1.0 mg/kg (titrate)
Electrolyte changes with loop diuretics:
Hypokalemia
Hypochloremia
A/E of loop diuretics:
Potentiation of NMBs
Presynaptic cAMP inhibition, ACh release
Drug interactions with loop diuretics:
Nephrotoxicity when administered with aminoglycosides and cephalosporins
Possible cross reactivity to sulfonamide allergy
Decreases renal clearance of lithium
Prototype drug for osmotic diuretics:
Mannitol
Site of action of osmotic diuretics:
Tubules
MoA of osmotic diuretics:
Increased osmolarity in tubule → Na+, Cl-, HCO3- excreted along with water
Concern with osmotic diuretics:
Increases plasma osmolarity and intravascular volume; can cause pulmonary edema in poor LV function
PK of osmotic diuretics:
Do not enter cells; must be given IV
Onset: 10 - 15min
Duration: 2 hrs
100% renally excreted
Indications for mannitol:
Differential dx of oliguria (after furosemide)
Prophylaxis for ARF
↓ ICP
↓ IOP
Dose of mannitol:
0.25 - 1 g/kg IV
Anesthesia concerns with mannitol:
Pulmonary edema
Hypovolemia
Electrolyte changes
Two classes of potassium sparing diuretics:
Epithelial Na+ channel blockers
Aldosterone antagonists
Prototype epithelial Na+ channel blocker:
Triamterene
Site of action of triamterene:
Collecting duct
MoA of triamterene:
Na+ channel blockade in the luminal membrane; non-competitive antagonism of aldosterone
A/E of triamterene:
Can cause hypERkalemia
Prototype aldosterone antagonist:
Spironolactone
MoA of spironolactone:
Competitive aldosterone antagonist; weak and usually combined with other diuretics
Indications for spironolactone:
HF Ascites Low-renin hypertension Hypokalemia Conn's syndrome
Prototype carbonic anhydrase inhibitor:
Acetazolamide
MoA of acetazolamide:
Blocks the action of carbonic anhydrase, increasing HCO3-, Na+, and H2O in urine
Indications for acetazolamide:
Glaucoma
Altitude sickness
ICP
