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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