Urea is a hyponatremia
treatment long forgotten in the United States
What do we know about urea? It
is a very
cheap powder (< $0.50/30 gram) that works
by increasing free water excretion through osmotic diuresis. Shown below is the solute excretion as a
determinant of free water excretion.
Free water
clearance = solute excretion/Uosm x
(1 - Uosm/Posm)
Physiologically it makes sense, but does it really work? In this
article, 13 patients with SIADH were tried on vaptans
(satavaptan or tolvaptan) for 12 months. Then vaptans were discontinued for 8 days and urea was started after ensuring that their Na level came down. The result? It worked as well as
vaptans! Side effects included hypernatremia and gastric irritation but no
osmotic myelinolysis has been reported with urea. It does not cause volume
overload (unlike salt), hypokalemia (unlike diuretics), or uremia. You will not
become uremic even if your BUN is 100 after you take urea (but you will be
urinating a lot!).
So why are we not using it? Are you a fan of bitter drinks? We know
Belgians are (great beer there!). In Belgium Canada
5 comments:
Another advantage of urea is that it has been shown that urea protects against the development of osmotic demyelination syndrome (ODS) when overcorrection of serum sodium occur. Aparently, urea causes rapid reaccumulation of organic osmolytes in the brain cells. That is why ODS occurs very rarely in chronic hemodialysis patients.
Thank you for sharing your insights, Dr. Rondon. It makes sense. We have to be careful about overcorrection anyway, and I think the potential protective effect of urea against ODS is a big plus given the grave prognosis of ODS. I appreciate your points.
An alternative in patients who find urea powder unpalatable is having the pharmcy compress it into tablets that can be swallowed whole. This means swallowing a number of relatively big tablets, but they have no taste. Routine practice, here in Belgium.
Dear anonymous, thank you for your comment based on your experience, I found it helpful. I was wondering if there is such an alternative option over there. T
Dear Dr Tsukahara ,dear collegues ,
Thank for your interest for urea .
Indeed it is easy to use (we treat the majority of our patients with SIADH with urea,some of them for more than 5 years and they get use generally over time (weeks) to the taste but which is greatly attenuated by the mixture with syrup (grenadine or another one),orange juice..For those who really cannot take urea like this , another alternative is to prescribe urea as effervescent preparation :( urea 10g + sodium bicarbonate 2g+ citric acid 1.5gr + sucrose 200mg )for each bag and patient takes for instance 2 bags/day (dose must then be adapted). Alain Soupart
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