11. Diuretics Flashcards
4 types of diuretics
- carbohydrase inhibitors
- loop diuretics
- thiazides
- potassium sparing diuretics
Mannitol - type of diuretic
Osmotic diuretic. Does not penetrate membranes (no reabsorption)
Mechanism of action of mannitol
Mannitol elevates blood plasma osmolality ➞ enhanced flow of water from tissues, including the brain and cerebrospinal fluid, into interstitial fluid and plasma ➞ cerebral edema, elevated intracranial pressure, and cerebrospinal fluid volume and pressure may be reduced.
Mannitol may also be used for the promotion of diuresis before irreversible renal failure becomes established; the promotion of urinary excretion of toxic substances; as an Antiglaucoma agent; and as a renal function diagnostic aid.
Mannitol. Indications
- life threatening edemas
- acute renal failure
- ophtalmology (e.g. as antiglaucoma agent to reduce intraocular pressure)
Carboanhydrase inhibitors. Place of action. Indications
Proximal tubule.
heart failure
glaucoma (systemic - local)
alkalizing urine!
Carboanhydrase inhibitors. Mechanism of action.
if CA is inhibited ➞ H2O and CO2 can not be created in the lumen from H2CO3 ➞
- HCO3 does not enter the cell and interstitium
- more H in the lumen (H2CO3 is formed from H and HCO3 in the lumen) ➞ increase of acidity of the urine
- less Na goes to interstitium ➞ diuresis
(Na/H antiporter on the luminal side;
Na/HCO3 cotransporter on the basolateral side)
Carboanhydrase inhibitors. Drugs. Side effects.
Acetazolamide, dorzolamide, brinzolamide
matabolic acidosis (less HCO3 in the system), other uroliths
Loop diuretics. MOA
inhibit Na/K/2Cl cotransporter in the loop of Henle ➞ Na and K excretion increases
Mg and Ca excretion increases
Most effective diuretics
Loop diuretics. Drugs. Indications.
FUROSEMIDE , torasemide
heart failure (primary dog)
edemas
oliguria. anuria
Loop diuretics. Side effects
SE:
hypokalemia
metabolic alkalosis (concentration of ECF containing sae amount of HCO3)
hypotension (Fe)
ototoxicity (toxic to ear, hearing problems)
Furosemide. Dosage
Dog: IV, IM, PO: 1-5 mg/kg BID, TID
Cat: IV, IM: 1-2 mg/kg BID, TID
PO: 0.5-2.5 mg/kg BID, TID
Horse: IV: 0.5-1 mg/kg BID
Thiazides. MOA
distal tubule: inhibition of NCCT (Na/Cl cotransporter) ➞ Na and water excretion increases
K excretion increases (K does not enter interstitium through K/Cl cotransporter bc there is not enough Cl)
Ca exretion decreases
Mild-moderate diuretics
Thiazides. Drugs. Indications
Hydrochlorothiazide. Chlorothiazides.
Rare usage
Ca oxalate urolithiasis
Combinations
2 types of potassium sparing diuretics
- Na channels blockers (amiloride)
- Aldosterone antagonists (spironolactone)
Potassium sparing diuretics - aldosterone antagonists. MOA.
Competitive antagonists
ENaC (epithelial Na channels) and Na/K- ATPase protein expression ⬇
increased Na excretion, K excretion unnchanged
mild diuretics
