From: Arthur.Saus@p160.f72.n376.z1.fidonet.org (Arthur Saus)
Newsgroups: misc.handicap
Subject: General Interest
Date: 28 Aug 92 16:15:43 GMT
Reply-To: Arthur.Saus@p160.f72.n376.z1.fidonet.org
Organization: FidoNet node 1:376/72.160 - Windows of the Worl, Columbia SC

Index Number: 24029

[This is from the Chronic Pain Conference]

Hello Linda!

15 Aug 92, Linda Cummings writes to Kathleen Mcintosh:

 LC> Guilty as charged!  I'm one of those people who just don't like to bother
 LC> anyone, and will writhe in pain before I call them for medication.  Of
 LC> course, by the time they get there, I'm cussing away wondering why it's
 LC> taken them so long.  [grin]  I guess I better change my attitude for the
 LC> next hospital stay (when my batteries run down).

The things you have been talking about are some of the reasons the
PCA device was invented and has become so popular.  There are a
number of reasons that hospital personnel may not seem as
responsive as needed to requests for pain medications.  Although
one of them is that the nurses who are responsible for
administering the pain meds are busy taking care of other patients,
this is not actually the major reason.

The real reasons deal with the pharmacokinetics and
pharmacodynamics of drug administration.  (a couple of big
words...but hang in there and I'll try to explain)  Any drug that
is administered has certain actions (the pharmacodynamics).  Some
of these actions are the desired drug effect such as pain relief,
but some of these actions are undesired drug effects such as
sedation, cardiac depression, dilation of blood vessels,
respiratory depression, hallucinations, euphoria, and even
addiction.

These effects happen over various amounts of time after the drug is
administered.  Now almost any drug is a foreign material to the
body and the body tries to get rid of it after it is given.  This
also takes time, but as soon as it gets there, the body starts to
work to try to get rid of it.  As a result, there is a constantly
varying level of a drug in the body after it is administered.
Initially, the drug concentration increases, but then it reaches a
peak and decreases as the body gets rid of it.  This time-related
changing of drug levels is pharmacokinetics.

Now, for each drug, there is a fairly standard way the body
metabolizes it or "clears it" from the body.  Although to some
extent these routes depend on well defined biochemical pathways to
metabolize the drug, the process is also much more complicated than
that.  Anyway, the net result is that a drug's duration of action
can be expressed in terms of a "half-life" of so many minutes or
hours or days.  The half life is not precise for a given drug,
since this time of its presence in the body depends on how the
person's individual body handles it, so "half-life" is expressed in
a wide range of time (for example: 3 to 6 hours).  It is easy to
measure the exact half life of a drug in a group of genetically
identical lab rats, but not easy at all to measure it precisely for
a given individual person.

Now the reason I've gone into this long discussion is to get to the
following: If a drug is given more frequently than at its
half-life, this leads to drug accumulation in the body.  If
repeated doses are given AT the drug's half-life, it maintains a
steady level, and a steady effect.  If it is given at intervals
that are longer than the half-life, the drug level slowly declines,
and the therapeutic effect will at some time decrease as well or
stop, even though the patient is still taking the drug.  This is
different from drug tolerance, which has an entirely different
explanation.

Going back to the pharmacodynamics, there is a "threshold" level of
drug concentration which is necessary for a drug to have a
noticable effect.  In other words, even though there is a certain
drug present in the body, it may have no effect if its
concentration is below a certain level.

Likewise, there is a ceiling concentration at which toxic effects
occur. Between the concentration that is the threshold and the
concentration that is the ceiling, lies the "therapeutic window".
The goal of drug therapy is to achieve a drug level that remains
between the threshold and ceiling, in this "window".  This is the
reason that compliance with a physician's orders as to the amount
of drug to take and dosing schedule are so important to maintain a
proper therapeutic effect.

Various things interfere with achieving optimal drug
administration, and most of them are very practical considerations,
not theoretical ones such as the biochemistry of how the drug
acts.  Most of us don't like to take medications, and "forget" if
there's not a pressing reason reminding us.  Even in the hospital,
the nurse may be busy with an emergency down the hall or some other
duty and can't get the drug administered at exactly the right
time.  Then because of pharmacokinetic variations, its difficult to
know exactly when the right time is for a given individual.

Even when the patient reminds the nurse that due to pain, another
injection or pill is needed, for narcotics there is a lot of
preparation and paperwork that must be done to keep track of these
carefully controlled narcotics (which have to always be kept locked
up in a locked cabinet which usually has double locks).  In other
words, even though narcotics are excellent pain relievers, they are
very difficult to properly administer.

I think I started out talking about PCA machines.  They bypass much
of the administrative problems because the narcotics are kept
locked in a PCA machine, very small doses are administered at any
one time, and they are administered instantly on demand.  The
patient administer it by pressing a button, and can get drug
administered every few minutes if it is needed that often.  If the
concentration in the body builds to the ceiling level, the effect
is a sedated patient who is too sleepy to remember to push the
button the next time for the next drug administration, so the body
continues to lower the drug level until again the patient is awake
enough to remember to push the button.  In other words, the system
has a built-in safeguard against overdosage, that could be bypassed
only on a Doctor's order (by changing it to a continuous infusion
mode rather than an "on demand" mode) or by some other well-meaning
individual pushing the button for the patient.  As you can see from
this discussion, this is a dangerous practice.

As long as we have to treat acute pain with narcotics, in my
opinion this PCA device is currently the optimal technology for
narcotic administration from both theoretical and practical
reasons.

Arthur

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