Diuretics

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Tip

Things affect electrolytes concentration

  1. Drug effect
  2. Can Na+ help
  3. Exchanger
  4. Charge
  5. Contraction
Diuretic Type Na+ K+ Cl- HCO3 Ca2+ Uric Acid
Loop (eg, furosemide) ↓↓↓ ↓↓ ↓↓↓ ↑↑
(Cl- loss, vol. contraction, RAAS →↑H+ secr, HCO3 reabs.)

Disrupts TAL lumen potential →↓Ca reabs.
Thiazide (eg, HCTZ, metolazone) ↓↓
Distal Na →↑K excr (RAAS).
↓↓


Cl- loss, vol. contraction →↑HCO3 reabs.

DCT Ca reabs (Na/Ca exch.).
Potassium sparing (eg, spironolactone, amiloride)
Spiro: Aldo effect. Amil: blocks ENaC in CD.

Spiro: Aldo-med. NaCl reabs. Amil: ENaC activity reduces passive Cl reabs.

H+ secr (Aldo block/Na reabs).
Carbonic anhydrase inhibitor (eg, acetazolamide)
Inhibits CA in PCT →↓NaHCO3 reabs.

Distal Na →↑K excr; Met. Acid. K wasting.

Hyperchloremic Met. Acid. (HCO3 loss compensatory Cl reabs with Na).

HCO3 reabs →↓Ca reabs; Met. Acid. →↑Ca excr.
TAL: Thick ascending limb of Loop of Henle

Carbonic anhydrase inhibitors


Agents

Acetazolamide

Mechanism of action

Thiazide diuretics


Agents

Mechanism of action

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Use thiazide with loop diuretics

Loop diuretics function by inhibiting the Na+-K+-2Cl- cotransporter in the ascending limb of the loop of Henle to block sodium absorption and encourage the excretion of sodium and water in the urine. However, the sodium excretion caused by loop diuretics is limited by the reabsorption of sodium in the distal convoluted tubule; the Na-Cl cotransporter in the distal tubule counteracts some of the effect of loop diuretics by absorbing much of the sodium that is not absorbed in the loop of Henle. Inhibition of the Na-Cl cotransporter with metolazone prevents reabsorption of the increased sodium delivered to the distal tubule, significantly increasing total sodium excretion.

Loop diuretics


Mechanism of action

Potassium-sparing diuretics


Agents

Mechanism of action

Adverse effects


Loop diuretics

Thiazide diuretics

Potassium sparing diuretics

Carbonic anhydrase inhibitors

Osmotic diuretics