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Flashcards in Diuretic Drugs Deck (16)
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List drug type, site, mechanism, indications, side effects...

Site 1 Diuretic: Carbonic anhydrase inhibitor, acts on proximal tubule. Decreases sodium-bicarbonate reabsorption in the proximal tubule, which results in more H+ and K+ ion excretion in the distal tubule. Can cause hypochloremic metabolic acidosis because of increased bicarbonate and K+ excretion (bicarbonate isn't recycled, leads to systemic acidosis).

Indications: glaucoma (decrease intraocular pressure), short term urinary alkalinization (excrete acid toxicants, dissolve some types of urinary crystals). Not good for long-term use because waning effect.

Side effects: calcium phosphate stones due to side effects of increased bicarb.


Carbonic anhydrase inhibitor actions

decrease sodium bicarb reabsorption in the proximal renal tubule and reduce formation of some transcellular fluids (aqueous humor)

not for long-term use

can lead to systemic acidosis


Loop Diuretics actions

Block Na/K/Cl cotransport in thick ascending limb of Henle's loop

example is Furosemide



List mechanism of action, type of drug

"Loop" Diuretic: Acts on site 2. Block NKCC2 transport proteins which inhibits Na/K/Cl cotransport in the thick ascneding limb of Henle's loop (counter-current exchange mechanism)

Increase Na+ delivery to the distal tubule, which can only partially resorb it, resulting in lots of the Na in the urine. Additionally decreases K+ recycling, reducing lumen electropositivity and reabsorption of Ca2+ and Mg2+ ions.

Net effect is hypertonic urine with lots of Na+, Cl-, K+, Mg++ and H+ in lots of water



route of administration, metabolism, site of action

given PO or parenterally

half undergoes phase 2 glucuronidation, half is excreted unchanged in urine

exhibits plasma protein binding, secreted into nephron


Furosemide Indications

(renal and one non-renal one in horses)

edema (rapidly decrease ECF volume), acute renal failure (increase urine flow and K+ excretion), toxicant ingestion (accelerate excretion), hyperkalemia, hypercalcemia, hyperthyroidism (I- secretion)

Also reduces exercise-induced pulmonary hemorrahage by decreasing blood volume


Furosemide in dogs

broad dose range, decrease BP, excrete NaCl and can possibly cause hypoglycemia


Furosemide in cats

narrow dose range, greatly decrease blood pressure, possible reversible otoxicitiy.


Furosemide adverse effects

hypokalemic metabolic alkalosis due to excretion of lots of K+ and H+

hypomagnesemia and hypocalcemia, dehydration, dilutional hyponatermia, ototoxicity leading to hearing loos esp if given with ototoxic drugs


Loop Diuretic drug interactions

Ototoxic drugs

NSAIDS- compete for transport into tubule

Glucocorticoids- enhance K+ depletion

Digitalis- hypokalemia increases activity and risk arrythmias



type, site, mechanism

Thiazide diuretic, acts on site 3 in early distal tubule to decrease salt reabsorption, Na + ends up being secreted.

Net effect is increased excretion of Na+, Cl-, K+, Mg++, H+ and water, and long-term increased Ca++ reabsorption.

Most NaCl and water is reaborbed before the early distal tubule so they are less effective.




type, site, mechanism, metabolism, elimination

Site 4 action, one of the K+ sparing diuretics

Directly blocks epithelial Na+ channels in principal cells of the late distal tubule and collecting duct, not dependent on aldosterone like spironolactone

short-term effects on normal K+ excretion

secreted into the proximal tubule, undergoes hepatic biotransformation to be converted to active metabolites, eliminated into urine, bind to plasma proteins



Acts on site 4 as a K+ sparing diuretic

Antagonist of mineralocorticoid receptors and inhibits aldosterone-mediated induction of epithelail Na+ channels decreasing distal Na+ reaborption

Dependent on presence of aldosterone

Decrease K+ excretion


Indications and contraindications of site 4 diuretics (spironolactone and triamterene)

Indications: hypokalemia, edema secondary to hyperaldosteronism

Contraindications: hyperkalemia or hyperkalemic metabolic acidosis, disease states that mask K+ balance

Can be combined with a site 2 or 3 diuretic for natriuretic effects



Osmotic diuretics

Inhibits water reaborption (proximal convoluted tubule, descending tubule, and collecting duct) and disrupts renal counter-current exchange, net effect is increasing water excretion

Given IV and filtered at glomerulus with no reaborption, no metabolism, excreted in urine


Indications and Contraindications of Mannitol use

Indications: acute renal failure, toxicant elimination, cerebral edema, glaucoma, etc.

Contraindications: edematous states liek CHF or overexpansion of blood volume, pre-existing dehydration