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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