Diuretics Flashcards
PCT
a) Major things reabsorbed here
b) main membrane transporter invovled
c) enzyme involved here
- responsible for 60-70% of total reabsorption of NA
- carries out isosmotic reabsorption of AA, glucose & many cations
- major site for reabsorption of Sodium Chloride& Bicarb
b) NHE3: apical membrane Na/H exchange via NHE3
Na/K ATPase is present in the basolateral membrane to maintain intracellular Na & K
c) Carbonic Anhydrase: bicarbonate is reabsorbed poorly through luminal membrane so it is converted to CO2 & H2O by Carbonic Anhydrase
TAL
a) Major things reabsorbed here
b) main membrane transporter invovled
c) enzyme involved here
- responsible for absorption of 20-30% of Na
- pumps out Na, K, Cl into interstitium
- major site for Mg & Ca reabsorption: positive potential in lumen allows Mg2+ and Ca2+ to be reabsorbed via paracellular pathway
b) NKCC2: reabsorption of Na, Cl & K via Na+/K+/2Cl- cotransporter
DCT
a) Major things reabsorbed here
b) main membrane transporter invovled
c) enzyme involved here
- reabsorption of 5-8% of Na
- actively pumps Na & Cl out of lumen via Na+/Cl- cotransporter NCC
- Ca also reabsorbed under control of PTH
b) NCC: actively pumps Na & Cl out of lumen (Na+/Cl- cotransporter)
c)
CD
a) Major things reabsorbed here
b) main membrane transporter invovled
c) enzyme involved here
- reabsorption of 2-5% of Na–last tubular site for Na reabsorption
- controlled by aldosterone, occurs via channels & is accompanied by equal loss of K or H ions
- primary site of acidification of union & K excretion
- Cl- reabsorbed via paracellular pathway because of negative lumen potential
b) ENaC: inward diffusion of Na via the epithelial sodium channel ENaC leaves lumen negative potential–> drives reabsorption of Cl- & efflux of K+
Carbonic Anhydrase Inhibitors
- acetazolamide
2. dorzolamide
Loop Diuretics
- Furosemide
- Bumetanide
- Torsemide
Thiazides
- Hydrochlorothiazide
Potassium Sparing Diuretics
- aldosterone antagonists: spironolactone & eplerenone
- Na channel Blockers: amiloride & triamterene
- ADH antagonists: Lithium & demeclocycline
Osmotic Diuretics
Mannitol
Acetazolamide
Carbonic Anhydrase inhibitor
Where do Carbonic Anhydrase Inhibitors Act
the PCT
Acetazolamide MOA & Effects & uses
inhibit CA both in the brush border & intracellular CA in PCT
Effects:
- Bicarbonate diuresis–>metabolic acidosis results
- Increased Na is presented to the CCD, where it is absorbed so more K is excreted–>causes significant K loss in urine–> HYPOKALEMIA
- CA inhibition in ciliary epithelium –>reduced secretion of aqueous humor
Uses:
- glaucoma
- urinary alkalinization for acidic drug toxicity
- tx acute mountain sickness
- significant metabolic alkalosis
drug used in high altitude sickness (mountain sickness)
acetazolamide (CA inhibitor)
acidosis of CSF results in hyperventilation
Uses of CA inhibitors
- glaucoma
- urinary alkalinization for acidic drug toxicity is salicylates
- tx acute mountain sickness
- significant metabolic alkalosis
Adverse Effects of Carbonic Anhydrase Inhibitors
- cross algernicity with other sulfonamides
- hyperchloremic metabolic acidosis
- renal stones: alkalization of urine by these drugs may cause Ca to precipitate –>renal stones
- Hypokalemia
How can CA inhibitors be used to treat glaucoma
CA inhibition in the ciliary epithelium –>reduced secretion of aqueous humor
Where do Loop Diuretics act?
Thick ascending limb
Furosemide
Loop Diuretic
Furosemide MOA & Effects & uses & ADR
Loop Diuretic, acts in TAL
- Inhibits NKCC2 (Na+/K+/2Cl- cotransporter)–>produce massive NaCl diuresis–>Edema fluid is rapidly excreted & blood volume is significantly reduced.
The Loop of Henle is the diluting segment, so blocking its function–>reduced ability to dilute urine
- also results in loss of lumen positive potential–>decreased reabsorption of ions like Ca & Mg–>Ca excretion is significantly increased
- More Na is presented to the CD–>it’s reabsorbed in exchange for K+ & H+–>hykalemic alkalosis
Uses:
- Tx of edematous states including HF & ascites
- *tx of acute pulmonary edema (LVF)
- mild to moderate CHF
- severe hypercalcemia
- seen commonly in malignancy (so we give large doses of furosemide with fluids & electrolytes)
ADR:
- *Hypokalemia–usually given with K sparing drugs
- ——->Hypokalemic metabolic alkalosis - Hypomagnesemia
- Hypocalcemia
- Hypovolemia
- *Ototoxicity–> don’t combine with other ototoxic drugs i.e. aminoglycosides
- cross hypersensitivity with sulfa drugs–> i.e. if allergic to sulfa drugs don’t use bc may also be allergic
Uses of Loop Diuretics
- Tx of edematous states including HF & ascites
- *tx of acute pulmonary edema (LVF)
- mild to moderate CHF
- severe hypercalcemia
- seen commonly in malignancy (so we give large doses of furosemide with fluids & electrolytes)
ADR of Loop Diuretics
- *Hypokalemia–usually given with K sparing drugs
- ——->Hypokalemic metabolic alkalosis - Hypomagnesemia
- Hypocalcemia
- Hypovolemia
- *Ototoxicity–> don’t combine with other ototoxic drugs i.e. aminoglycosides
- cross hypersensitivity with sulfa drugs–> i.e. if allergic to sulfa drugs don’t use bc may also be allergic
Site of action of Thiazides
Distal Convoluted Tubule
Hydrochlorothiazide
MOA
Uses
ADR
Thiazide, acts in Distal convoluted tubule
MOA: inhibits Na/Cl transporter (NCC) in early segment of distal convoluted tubule
Uses:
- HTN (Mild-moderate essential HTN)
- Chronic renal calcium stone (bc reduce urine Ca concentration)
ADR:
1. severe hyponatremia
2. hypokalemia
3. cross hypersensitivity w sulfonamides
4. hyperuricemia–>gout
(direct competition of thiazides for rate transport)
5. Hyperlipidemia–>increase serum CH & LDL 5-10%
6. Hyperglycemia due to diminished insulin secretion in patient with preexisting type 2 diabetes
Effects of Thiazides
- sustained Na & Cl Diuresis
reduction in transport of Na into tubular cell reduces intracellular Na –>promotes Na/Ca exchange
——->results in increased reabsorption of Ca from urine –>urine Ca content is decreased
- Reduces BP
initially decrease CO bc decrease blood volume, but later decrease TPR bc decrease Na concentration & Na is responsible for maintaining vessel stiffness.
Uses of Thiazides
- HTN (Mild-moderate essential HTN)
2. Chronic renal calcium stone (bc reduce urine Ca concentration)
Thiazides ADR
- severe hyponatremia
- hypokalemia
- cross hypersensitivity w sulfonamides
- hyperuricemia–>gout
(direct competition of thiazides for rate transport) - Hyperlipidemia–>increase serum CH & LDL 5-10%
- Hyperglycemia due to diminished insulin secretion in patient with preexisting type 2 diabetes
Potassium sparing Diuretics act in the
Collecting Duct
Downside of Potassium sparing diuretics & compensation
Weak therefore rarely used alone; Exception = hyperaldosteronism
Spironolactone
Aldosterone antagonist; K+ sparing diuretic
Amiloride & Triamterene
K+ Sparing Diuretics that directly block Na channels in CD
How do K+ Sparing Diuretics work
Inward diffusion of Na via epithelial sodium channel levels a lumen-negative potential which drives reabsorption of Cl- & efflux of K+
Spironolactone MOA, Effects, Uses, ADR
Antagonist of Aldosterone in Collecting Duct
MOA: by binding & blocking the aldosterone receptor–>reduce expression of genes controlling synthesis of epithelial Na ion channels & Na/K ATPase–>this increases sodium excretion bc less Na is being reabsorbed
Effects:
- increases Na excretion
- Decreases K+ & H+ ion excretion (bc whenever Na is reabsorbed K is exchanged & excreted
- may cause hyperkalemic metabolic acidosis
Uses:
- Hypokalemia causes by loop diuretics & thiazides
- Aldosteronism (occurs in cirrhosis; also seen in Conn’s syndrome & with late HF
ADR:
- Hyperkalemia–>can cause cardiac arrest
- Extreme caution needed when given with ACE-inhibitors bc both inhibit aldosterone
- gynecomastia (painful, enlargement of breast in males) hirsutism (excess body hair growth), loss of libido & impotence
- –>all from anti-androgenic effects
gynecomastia (painful, enlargement of breast in males) hirsutism (excess body hair growth), loss of libido & impotence
all from anti-androgenic effects of spironolactone
Osmotic diuretics work where
PCT (where majority of isosmotic reabsorption occurs)
Mannitol
Osmotic diuretic; acts in PCT; given by IV
freely filtered in glomerulus but poorly reabsorbed, so it remains in the lumen
Holds water by virtue of its osmotic effect