Osmotic Diuretics
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Osmotic diuretics e.g. mannitol

These are basically just drugs that are filtered at the glomerulus and then not reabsorbed along the nephron, thus resulting in a greater osmotic pressure within the tubular fluid, and so less water is reabsorbed, and more is excreted.
These drugs will also cause a natriuresis (loss of sodium in the urine) because the osmotic gradient prevents sodium being reabsorbed properly.
It can also cause hypokalaemia due to loss of potassium.
It causes an increase in blood and extracellular fluid volume when first administered, and thus can precipitate heart failure.
It has a short half-life except in renal impairment.
It is not used very often clinically in relation to the kidney and blood pressure. Its main used in is brain injury, where, as it does not cross the blood/brain barrier it can be useful in preventing cerebral oedema, thus limiting ischaemic damage.

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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) currently works as a GP Registrar and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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