Nephrology · USMLE Step 1 and Step 2

Osmotic Diuretics - Mannitol song

Osmotic Diuretics: Mannitol - Mechanism & Uses, as a song. Hear the short teaser here. The full song is on YouTube and Spotify.

Osmotic Diuretics - Mannitol

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Key points in this song10

Mannitol is an osmotic diuretic that increases tubular fluid osmolality, drawing water into the tubular lumen and preventing its reabsorption, primarily in the proximal tubule and descending loop of Henle.
Mannitol is freely filtered at the glomerulus but not reabsorbed or secreted, making it the classic example of an osmotic diuretic.
First-line agent for reducing elevated intracranial pressure (ICP) by creating an osmotic gradient that draws water out of brain parenchyma into the vasculature.
Used to reduce intraocular pressure in acute angle-closure glaucoma when other agents fail or are contraindicated.
Administered IV only — mannitol is not absorbed orally, so it must be given intravenously to exert its systemic osmotic effects.
Mannitol initially expands plasma volume before diuresis occurs, making it contraindicated in pulmonary edema and congestive heart failure due to risk of fluid overload.
Used in oliguric acute kidney injury to promote urine flow and prevent tubular cast obstruction, particularly in rhabdomyolysis and hemolysis.
Classic adverse effect is pulmonary edema from the transient intravascular volume expansion that precedes diuresis.
Mannitol can cause hypernatremia with prolonged use, as free water loss exceeds sodium loss, raising serum sodium concentration.
Contraindicated in anuria, as the inability to excrete mannitol leads to dangerous osmotic expansion and pulmonary edema.