Urea can be an effective medication for people suffering from Ménière's Disease. In ears affected by Ménière's
Disease there is an excess amount of fluid inside the membranous labyrinth.
This fluid is called endolymph and too
much endolymph is called endolymphatic
hydrops.
Here are a few simple facts about Urea and the way it can be used.
Background
Urea is an osmotic diuretic. It has a very simple chemical formula CO(NH2)2. It is a major constituent of
urine and the fertiliser put on the ground is often
made from cattle urine. Those who take Urea to control their Ménière's Disease will be relieved to know that the Urea
used medically is made chemically rather than biologically!
Urea is one of several osmotic diuretics. These substances alter the osmolarity of the blood. If the blood becomes hyperosmotic, fluid from the surrounding tissues will be
'sucked' into the blood causing some dehydration. The inner ear is very
sensitive to changes in blood osmolarity and the
correct dosage of Urea can result in the removal of fluid from the inner ear
without undue dehydration of the body.
The first osmotic diuretic to be described was glycerol. Klockoff
and Lindblom first described the effects of glycerol
dehydration in ears affected by Ménière's Disease in
1963. They showed that if a person suffering from Ménière's
and a fluctuating hearing loss takes glycerol, the hearing in the affected ear
may improve temporarily. The improvement in hearing can only occur when the
hearing is poorer than usual. For sometime there was a controversy and some
researchers denied glycerol altered the amount of endolymphatic
hydrops within the ear. The first evidence that the
electrical potentials with the ear were altered by glycerol was described by my
colleagues and myself in 1978.
Initially glycerol was used as a diagnostic test but soon it was also used
therapeutically if a person suffering from Ménière's
disease suddenly lost hearing as it could recover the hearing. The main problem
with glycerol was its taste and the large volume that had to be consumed. A
dosage of 1 - 1.5ml per kilogram body weight is needed. Thus a
80 kilogram person needs to drink 120 mls of a thick
oily fluid which tastes like diesel fuel.
Urea is also an osmotic diuretic and smaller quantities are required. 30gm
of Urea is the usual dose, which will dissolve in less than 30ml of water or
fruit juice. It tastes a bit like urine (I have not tried comparing the tastes
of these liquids myself but I am assured this is so!).
In Japan, Isosorbide is now one of the commonest treatments for Ménière's Disease. It tastes sweeter than sugar. A dosage
of 1ml / kg body weight is required. In Australia,
100ml of Isosorbide costs about $30.
Professor Jan Stahle used regular dosages of Urea
to treat Ménière's Disease in Sweden.
He reported that the hearing was better maintained over time and the patients
had fewer attacks of vertigo compared to a control group. Based on his work I
began to use Urea in 1980 for people suffering from Ménière's
Disease.
How it works
It seems likely that once an ear has been affected by Ménière's
Disease (stage 1 or 2), that an increase in the volume of endolymph
may trigger an attack of vertigo. The established theory is that the increase
in volume of endolymph causes a pressure sufficient
to burst the flimsy membrane inside the inner ear causing the different fluids
inside the ear to mix together paralysing the balance
nerve and causing vertigo. My own theory is that the increased fluid triggers a
period of rapid drainage from the ear causing the attack of vertigo. Either
theory can explain why removing some fluid from the inner ear may prevent an
attack from occurring.
How it is taken
There are different purposes for which Urea can be used:
To prevent an attack of vertigo from occurring. If
someone knows an attack of vertigo is imminent, a dose of Urea may prevent the
attack from occurring. This is because the Urea decreases the volume of endolymph sufficiently to prevent the endolymph
from reaching the critical level that triggers the attack.
The person must have sufficient warning to be able to take the Urea; at
least 5 minutes is needed. Once the attack of vertigo has commenced, Urea is no
help and may make matters worse. Rarely, the Urea may only postpone the attack
for 3-4 hours rather than prevent the attack.
To secure a period of freedom from attacks. If
someone is suffering frequent attacks of vertigo and especially if the attacks
can be triggered by stress, then Urea can be taken to secure a period free from
attacks. For instance if that person has to attend an
important function such as a wedding, the Urea can be taken immediately before
the event and it is unlikely that any attack can occur until the Urea has worn
off. This provides most people with a freedom from attacks period of at
least 3 hours.
I call it the 'Cinderella medicine' as when the 3 hours has expired, the
person can start having the attacks again.
As a regular medication to prevent the progress of Ménière's Disease. A few hardy souls take Urea on a
regular basis to reduce endolymphatic hydrops and to control their Ménière's
Disease. For most people, Urea tastes so revolting that its use is restricted
to occasional use.
How is Urea taken?
Urea comes as fine white granules. Some chemists measure 20gm or 30gm into
individual sachets. Other chemists supply a measuring spoon. Urea must be kept
dry, for when water combines with Urea it gives off ammonia and becomes
ineffective. If the Urea has congealed into large lumps, it is not worth
taking.
Unfortunately Urea cannot be taken in powder form inside a capsule. When the
capsule dissolves in the stomach, the neat Urea would damage the cells, as it
is so hydrophilic. In simpler terms the Urea crystals would suck the fluid out
of the cells lining the stomach. So Urea has to be combined with a small amount
of water or fruit juice and swallowed immediately before it decomposes to
ammonia.
I recommend that only an eggcup full of fluid is added to the Urea. Some
people prefer fruit juice to hide the taste of the Urea. I am told mango juice
is the most effective. The person then swallows it as quickly as possible. I
found it best to do so in a single gulp like swallowing a measure of whisky.
After drinking the Urea, no other fluid can be drunk but it is possible to eat
a biscuit, which will take some of the taste away from the tongue.
Urea is a natural substance in the body. Too much Urea causes a medical
problem called uraemia. Uraemia
is common in people who have kidney failure and results in a pale skin and an odour of stale urine on the breath and in the sweat. The
excess urea damages the liver. To avoid any possibility of uraemia,
the person must not take more Urea in a single day in grams than their own body
weight in kilograms (kg). For a person weighing 60kg, the maximum daily dose is
60gm, and for a 120kg person, the maximum daily dose is 120gm. If someone
weighs less than 70kg, then a single dose of 20gm is usually sufficient. For
heavier people I usually recommend a 30gm dose.
I have prescribed Urea for patients suffering from Ménière's
Disease for over 20 years and I am unaware of any major complications ever
occurring. Some people cannot tolerate the taste or do not find Urea helps. For
others, Urea has been a very useful adjunct to their regular medication.
References:
- Klockoff
I and Lindblom U (1963) Endolymphatic
hydrops revealed by glycerol test: preliminary
report. Acta Otolaryngologica
(Stock), 61: 459-462
- Moffat DA, Gibson WPR and Ramsden RT (1978) Transtympanic
electrocochleography during glycerol dehydration.
Acta Otolaryngologica
(Stock), 85: 155-166
- Angelborg
C, Klochoff I and Larsen HC (1982) Hyperosmotic solutions and hearing in Ménière's Disease. American Journal of Otology, 3:
200-203
- Stahle
J. Personal communication.
Table Of
Osmotic Diuretics (Dose for an 80kg person)
|
Substance
|
Cost
|
Dose
|
Taste
|
|
Urea
|
inexpensive
|
30ml
|
tastes like urine
|
|
Glycerol
|
inexpensive
|
120ml
|
tastes like diesel fuel
|
|
Isosorbide
|
very expensive
|
80ml
|
tastes like very sweet sugar
|
Footnote (from the Ménière's
Support Group of NSW):
Pharmacies should be able to supply Urea
but some pharmacists may not be familiar with it. Usually it comes in
containers of 100gm or 500gm. Check the price. If you
take Urea frequently, you may find that it cheaper to buy it 500gm at a time.
Macquarie Street Pharmacy sells a 500gm
plastic jar of Urea crystals for $36.95 (as of March 2003). This is a good
price. They will post it anywhere in Australia (postage is extra). If you need it urgently, it can be sent Express
Post. You can telephone your order and pay by credit card. If you ask, they
will include a measuring vial. We recommend them.
Macquarie
Street Pharmacy
195
Macquarie Street
Sydney 2000
Phone:
02 9221 1622
Fax:
02 9221 1296
If you don't have a measuring vial, you
can measure out the dry crystals by volume (eg with a
medicine measuring glass) before dissolving them in water. A dose of 20gm is
equivalent to about 27ml of the dry crystals by volume while a 30gm dose is
about 40ml of the dry crystals by volume.
The amount of water mentioned by Professor
Gibson (30ml of water to dissolve a 20gm dose of Urea crystals) is the very
minimum amount needed and it may be necessary to use a little more to get all
the crystals to dissolve. For a 30gm dose, about 45ml of water is needed to
dissolve the crystals.