Emu Cream Assists
Lidocaine:
Local Anesthetic Absorption Through Human Skin
(Excerpts)
88th AOCS Meeting, May 1997
Ratite
Oils: Processing and Applications
Presented
by Dr. William Code
Lidocaine is probably the most
common used local anesthetic.
For those of you with an organic chemistry of biochemistry
background, it’s an amide.
An amide local anesthetic is a much safer agent to use; as
it is less likely to cause an allergic reaction.
In fact, until a few years ago it was reportable if you got
an allergic reaction to an amide local anesthetic.
The other groups are the esters and are much more likely
to give you a reaction because they contain para-amino-benzoid-acid
(PABA) which a lot of us have been sensitized to in our sunscreens
and other products.
Lidocaine
is also reasonable in cost and readily available. It’s the most understood local anesthetic and a prototype in
general.
Most
ideas aren’t new ideas. The
concept of emu oil as being useful for any number of things primarily
originated from the people who have used it for many centuries.
Actually, some of the oldest people on Earth, as far as the
time that they’ve been here, are the Australoid race, or the Australian
Aborigines.
The
problem I wanted to address as something to thing about is the problem
with punctures in the skin of planned-for-needle insertion.
The obvious one that comes to mind to an anesthesiologist
is to start an intravenous drugs. We want to know in a few seconds whether the anesthetic is
working or not.
Vaccination
is an interesting example.
In the last few months, all of the post-secondary students
in British Columbia were vaccinated for measles after an outbreak
in Vancouver. It’s
a large group because the hepatitis B and the German measles vaccines,
of course, are given to the early preteens and that’s often a group
that we recognize, certainly, as anesthesiologists.
As young people, particularly in the preteen and early teen
years, that can get very anxious and upset about an injection.
If something were available to minimize that trauma, life
could be a lot simpler for public health nurses and other personnel.
Suturing
of wounds is always a tough consideration – the decision is whether
to put the local anesthetic in, and make two or three holes, or
just go straight ahead and suture with a tiny needle.
If you had a relatively sterile entity that could numb it
either before the injection with the needle, or with regard to the
wound itself, then you might be a lot further ahead.
Laser
therapy typically is done with injection and can be quite painful
in some parts of the body, as most of you are aware, especially
the pain of the hand or the base of the foot.
The
traditional over-the-counter preparation in both Canada and the
U.S. is EMLA cream, which stand for eutectic mixture of local anesthetics.
It has lidocaine in it and another agent called prilacaine.
It doesn’t work as well as I’d like it to.
It has a relatively slow action, a minimum of 45 minutes,
so that requires pre-planning. If you’re going to see somebody in
an operating room suite, it literally has to be put on by someone
at your suggestion beforehand, or you have to get the parent to
purchase it at home and put it on.
Do they put it on the right place?
Do they put it on in the right amount?
How does it proceed from there?
Unfortunately now, many pediatric institutions are withdrawing
or reducing their use of the cream because it’s been somewhat erratic
as to whether it’s actually served a purpose or not.
It’s often built up impressions and potential feelings, but
sometimes those have been very disappointed in the actual use thereof.
The
emu substance used in this particular pilot study was what I call
a cream, the thick version of the refined product versus the clear
oil.
What
did we test? We created
two mixtures that looked, for intents and purposes to people observing
them, the same. Quite
honestly, if they would have tasted them, they would have had a
considerable difference because all of the local anesthetics are
very bitter. It doesn’t
take a rocket scientist to tell when you’ve got one in your mouth.
As any of you know who have ever had a local anesthetic sprayed
in your mouth, for a sore throat of whatever, almost all of them
are very bitter.
Anyway,
our substance was emu cream and spearmint oil.
We use the spearmint oil for two reasons: the relatively
positive scent it imparts to most people and it has the advantage
that it may enhance absorption as well.
Our second preparation was emu cream of the same batch, Canadian
emu oil and spearmint oil again, with lidocaine.
Those
were then applied to two sites on six people.
The tow sites were both chosen as the same and that’s in
the ventral distal foreman, that is on part of your wrist which
hardly ever has any hair on it.
You can start intravenous there.
Usually, they’re not your large veins, but they work really
well and they’re exquisitely tender – therefore, good site to test
if you were able to use it.
The mixture was applied on both forearms on a two-inch square
sites, and then covered with something called Opsite, Tegaderm,
or one of the other proprietary units which are a lot like Saran
Wrap with a sticky surface around it.
The
function of the cover is twofold.
First of all, you increase the warmth and moisture in the
area and that might make a difference in penetration.
Also, it usually permits an increased concentration crossing
across the skin before it’s rubbed off or taken away.
After twenty minutes, that cover was removed and residual
cream was wiped away. The
amount of residual cream left is usually diminished over a time
frame.
We
then did two major tests on the individuals.
The common one we used initially was ice. That’s because in my practice in the operating room.
I found that if you can check with an ice cube where people
can tolerate the ice cube, and not tell when they’re going to have
sharpness from the incision with the cold hard steel knife.
Then, of course, we used pinpricks because most people were
kind of intrigued with the idea that this actually made any difference.
Because each individual had the substance A or B in each
instance, and ; correspondingly, the observer of the ice and pin
pricks was also blinded.
We
got fairly simple results in that there was a reduced sensation
noted in only one of the two arms, one skin site only.
Also, fortunately the one with the reduced sensation had
been treated with mixture B, which was the emu cream, the spearmint,
and the lidocaine combination.
That’s
something that might be vary – a larger size might make a difference.
You might get a difference too, if you went on other areas
which may have more thickened skin.
In
the discussion, this has to be done with co-called consistent, proven
pain stimulus. The
pain and temperature, just for those that aren’t as comfortable
with the physiology, are virtually teted by the same thing.
What I mean is, acute sharp pain, and warm and cold sensations,
tend to be affected and carried by the came fibers and the same
components of the spinal cord.
It’s not that same as the burning of dull pain that starts
after a few seconds. That
in a different type of pain fiber again.
When
we’re talking about the next step, the clinical trial, we’ll need
to start with adults. Where
we want to use it is in children, but typically, you can’t have
much success with the groups within the hospitals discussing the
study unless it’s been proven on adults.
Of
course, the million dollar, multinational question if “Will emu
oils work?” “Which ones will work better?” “Is there a particular
feature in emu oil that does work better?”
I know that people have tried local anesthetics on their
own, and local anesthetics in mineral oil.
Whether they’ve tried it in pure oleic acid, I don’t know.
What’s
the potential use in animals?
I feel certainly there is a good possibility in some of the
thinner skinned animals. I
think of horses, particularly, and probably dogs where you might
be able to apply the cream, and not require near as much sedation
of other entities.
In
general, we need more study with design and data acceptable for
publication in a peer-reviewed medical journal.
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