Diuretics

Question 1

Acetazolamide
Dichlorphenamide
Methazolamide

Answer 1

Carbonic Anhydrase Inhibitors (CAIs)
Mechanism: in proximal convoluted tubule (PCT)
decrease HCO3- reabsorption and formation in kidney

Uses:
glaucoma= decrease aqueous humor production
acute mountain sickness= decrease CSF formation and pH of CSF increasing ventilation and diminishing symptoms
Urinary alkalinization= increases urinary pH–>increase weak acid excretion
edema= with other diauretics

Adverse effects: hyperchloremic metabolic acidosis, renal stones, renal potassium wasting

Contraindication: cirrhosis (increases plasma NH4+)

Question 2

Mannitol
Glycerin
Isosorbide
Urea

Answer 2

Osmotic diuretics
Mechanism:
Proximal tubule and descending loop of Henle
increase fluid osmotic pressure–>decrease fluid reabsorption

Uses: prophylaxis of acute renal failure, cerebral edema, dialysis disequilibrium syndrome, acute attacks of glaucoma

Adverse effects: expansion of extracellular fluid volume (bad for pts with heart failure or pulmonary congestion), hyponatremia, hypernatremia (too much water loss)

Contraindications: anuria (renal disease), impaired liver function, active cranial bleeding, hyperglycemia

Question 3

Furosemide
Bumetanide
Ethacrynic acid

Answer 3

NKCC inhibitors (loop diuretics)

Mechanism:
Thick ascending limb
inhibit Na+-K+-2Cl- cotransporter–>inhibit reabsorption of solute from TAL segments, increase Ca2+ and Mg2+ excretion
vasodilation decreases right atrial and pulmonary capillary pressure

Use: pulmonary edema, congestive heart failure, acute renal failure, hypercalcemia, liver cirrhosis, drug overdose, hyponatremia

Adverse effects: hyponatremia, hypokalemia, hypocalcemia, hypomagnesia, otoxicity, hyperuricemia

Question 4

Chlorthiazides
Metolazone
Indapamide
Hydrochlorothiazide

Answer 4

NCC Inhibitors (Thiazides & Sulfonamides)

Mechanism: 
distal convoluted tubule 
inhibit Na+-Cl- cotransporter-->decrease Na+ and Cl- reabsorption
decrease Ca2+ excretion
vasorelaxation (increased Ca2+)

Uses: hypertension, control edema, hypercalciuria, nephrolithiasis, nephrogenic diabetes isipidus

Question 5

Amiloride, Triamterene

Answer 5

Inhibitors of renal epithelial Na+ channels

Mechanism:
Late DCT and collecting ducts
block epithelial Na+ channels

Use: K+ sparing agents in hypokalemic alkalosis, used in combo with loop diuretics/thiazides to prevent hypokalemia

Adverse effects: hyperkalemia, glucose tolerance, photosensitization, interstial nephritis, renal stones

Contraindications: hyperkalemia

Question 6

Spironolactone

Eplerenone

Answer 6

Aldosterone-Receptor Antagonist

Mechanism:
Renal collecting tubules
bind aldosterone receptors–>decrease Na+ reabsorption (natriuresis)
decrease loss of K+ in exchange for Na+

Use: 
prevent LV remodeling and cardiac fibrosis
prevent sudden cardiac death
decrease BP
edema and hypertension
added to therapy of heart failure
hyperaldosternoism 
refractory edema associated with secondary aldosteronism (cardiac failure, hepatic cirrhosis, nephrotic syndrome)

Adverse effects: hyperkalemia, metabolic acidosis (cirrhotic pts), effects due to biding other steroid receptors (gynecomastia, decreased libido, hirsutism, deepened voice, menstrual irregularities)