Osmotic diuretics cause water to
be retained within the proximal tubule
and descending limb of loop of Henle
(freely permeable to water)
Mannitol
(Osmitrol) is an example of osmotic
diuretic.
Clinical Use: mainly used to
reduce increased intracranial pressure;
Osmotic diuretics: properties
mannitol
(Osmitrol) : not metabolized, freely
filtered at the glomerular
usually administered by
IV; oral administration results in an
osmotic diarrhea-- perhaps useful to
promote elimination of toxic substances
from the GI tract (in conjunction with
activated charcoal)
urine volume increases
with mannitol excretion due to direct
osmotic effects
sodium
reabsorption is reduced because
of increased urine flow rates
{decreased contact time between
urine and tubular epithelial
cells}
Clinical Uses:
To increase urine
volume:
may be used to
prevent anuria if the kidney due
to hemolysis or rhabdomyolysis is
presented with a large pigmented
load.
when renal
hemodynamics are compromised
To decrease
intracranial or intraocular pressure:
Mannitol (Osmitrol)
extract water from intracellular
compartments, reducing total body
water
Following IV
administration, intracranial
pressure falls within 60-90
minutes.
Toxicity:
Volume expansion effects --
increased extra cellular fluid volume and
hyponatremia may cause pulmonary edema,
complicating congestive heart failure
Headache, nausea, vomiting
-- commonly observed
Dehydration and hypernatremia:
fluid loss leads
to significant dehydration and in
the absence of adequate fluid
replacement leads to
hypernatremia.
Ives, H.E., Diuretic Agents, in:
Basic and Clinical Pharmacology, (Katzung, B. G., ed)
Appleton-Lange, 1998, pp 242-259.
Osmotic diuretics cause water to
be retained within the proximal tubule
and descending limb of loop of Henle
(freely permeable to water)
Mannitol
(Osmitrol) is an example of osmotic
diuretic.
Toxicity: