Diuretics Flashcards
Things reABS in PCT
glucose, 60-70% of Na+, NaHCO3, AA
Carbonic anhydrase must be present on the lumenal membrane for the reabsorption of HCO3
action site of acetazolamide
Loop of Henle activities
H2O is lost in the descending limb into the medullary space by osmotic pull (action site of osmotic diuretics)
Ascending limp is impermeable to H2O but active NaCl reabsorption happens via Na-K-2Cl co transporter (action site of loop diuretics)
DCT Activities
Impermeable to H2O.
NaCl reabs occurs via Na/Cl cotransporter.
Ca++ reabs via Na/Ca exchange on basal membrane (regulated by parathyroid hormone)
action site of Thiazide diuretics
Collecting Tubule Activity
Site of regulation via aldosterone.
Weak diuretic action due to small amount of NaCl reABS here, but large role in final urinary K+, Na+ and H+ content.
Principal Cell Activity (CT)
Na+ and K+ channels exist on the luminal side. driving force of Na INTO cell exceeds the force driving K OUT of a cell. SO K excretion is coupled to Na reABS
Any diuretic that increases Na delivery to this area of the nephron will enhance K excretion (K+ wasting)
Potassium SPARING diuretics act by blocking this Na+ channel (decreasing Na+ reABS) OR antagonize the aldosterone receptor
Aldosterone activity
Increases number and activity of Na+ and K+ luminal channels and the Na/K pump on principal cells
Antidiuretic hormone (CT)
CTs are impermeable to H2O w/o ADH (vasopressin)
When ADH is present, AQP2 (aquaporin) channels are inserted on the luminal membrane, allowing for H2O absorption
Ethanol is an ADH release inhibitor
Thiazides MOA
inhibits NaCl reABS by inhibiting the Na+/Cl- cotransporter in the early segment DCT
overall effect: NaCl diuresis and decreased Ca++ excretion
Thiazide Uses
Hypertension (esp. in blacks and elderly)
CHF
Hypercalcuria - reduces urinary excretion of calcium adn therefore incidence of kidney stones
Thiazide adverse reactions
Hypokalemia - not advised in patients with arrhythmias, MI hx
hyperuricemia - avoid in patients with gout
Loop of Henle Agents (high ceiling diuretics)
Inhibits NaCl transport via Na+/K+/2Cl- transporter in ascending loop.
Have the greatest diuretic effect due to the length of the portion of nephron they act upon
Associated w/ increase in Mg++ and Ca++ excretion.
Effects RAAS and prostaglandin systems and therefore increases renal blood flow
Loop Diuretic Uses
Acute pulmonary edema - rapid reduction of extracellular fluid and venous return
Refractory edema - used if no response to Na+ restriction or thiazide diuretic
Hypercalcemia
CHF - if THZs are not strong enough in action
Loop Diuretic Adverse Reactions
Hypokalemic metabolic alkalosis –> enhances secretion of K+ and H+
Ototoxicity –> esp ethacrynic acid
Hyperuricemia/hyperglycemia
hypomagnesemia
Overdose –> rapid blood volume depletion
Potassium-Sparing Diuretic Drugs
Spironolactone*
Eplerenone*
Triamterene*
Amiloride*
Loop of Henle Drugs
Lasix (furosemide)*
Demadex (torsemide)
Ethacrynic acid (non-sulfonamide options)
Thiazide Duretic Drugs
Hydrochlorothiazide*
Chlorthalidone
Potassium Sparing Diuretics
Only mild diuresis possible if used alone due to their action site - Collecting Tubules
very small NaCl rabs here, weak diuretic effect
Spironolactone/Eplerenone
Competitive antagonist at the aldosterone receptor, blocks ALDO effects at collecting tubule, NOT allowing Na+ to be reabs –> lumen potential is more positive –> less K+ and H+ move into the urine
Triamterene/Amiloride
Directly blocks Na+ channels on collecting duct lumen to decrease Na+ reabs. (thus decreases coupled K+ secretion)
Spironolactone Clinical Use
primary hyperaldosteronism, hypokalemia, hypertension (in combo w/ thiazides), hirsutismof PCOS (blocks androgen receptor)
BOTH spironolactone and Eplerenone - CHF and HTN
Triamterene/Amiloride Clinical Use
CHF and edema of secondary hyperaldosteronism
Potassium Sparing Diuretics Adverse Reactions
Hyperkalemia and metabolic acidosis (H+ comes along with K+)
Spironolactone can block androgen receptor causing gynecomastia
Carbonic Anhydrase Inhibitor Drugs
Acetazolamide (Diamox)
Dorzolamide (Trusopt)
Carbonic Anhydrase Inhibitor MOA
Inhibition of enzyme depresses NaHCO3 reabsorption in PCT
Inhibits formation of aqueous humor that is dependent on HCO3 transport
Carbonic Anhydrase Clinical Uses
major uses NOT as diuretic
Glaucoma, urinary alkalinization, chronic metabolic alkalosis, acute mountain sickness
Osmotic Diuretic Drugs
Mannitol - given parenterally, poor oral absorption.
Osmotic Diuretics MOA
Limits H2O reabsorption in PCT and descending LOH and CT by overcoming osmotic force for H2O to leave
DOES NOT effect Na+ reabsorption
Osmotic Diuretics Clinical Use
increase urine volume in acute renal failure
Rapidly reduce ICP in head injury (decr. ECV, cant cross BBB)
acutely reduces intraoccular pressure in glaucoma
Osmotic Diuretics Adverse reaction
Initial hyponatremia as an acute effect of expansion of ECV by pulling water out of cells initially
chronic use w/o water replacement can cause hypernatremia (Na+ loss in the urine is less than water loss)
