Download What happens when a person is given a drug? When a person is

What happens when a person is given a
How does the drug get carried to the
various parts of the body?
When a person is given a drug – either by mouth
or into the back passage (rectum) – the drug
finds its way into the blood stream. The blood
carries the drug to the area where it is needed,
e.g. the brain in people with epilepsy.
Some drugs need to be carried by ‘plasma protein’
through the blood stream to various organs. The
plasma protein is just like a passenger train,
allowing the drug to ‘hop on’.
drug?
Case Illustration:
My daughter was given an anti-epileptic
drug and had no side effects, but it did not
control her seizures.
She was then
prescribed an additional drug and started
showing side effects. Should I stop the
additional drug?
Not necessarily. If a person has shown no
side effects when given one type of anti
epileptic drug (AED), and suddenly shows side
effects on being given an additional AED, it is
easy to think that it is the second drug that is
causing the problem.
How does the drug get into the blood
stream?
The internal organs between the mouth and the
rectum (see picture below) are known as the
‘gastro-intestinal tract’ (GI Tract) or the ‘gut’.
While the drug is on the ‘passenger train’ however,
it is not in its active state. That is, the drug will
have no effect on the body – it is as if the
passengers are all asleep. It is not until the drug
has been released from the plasma protein (or has
hopped off the passenger train) that it becomes
active again.
However, this may not be the case. If a
person is given two different types of antiepileptic drug (we shall call them ‘AED 1’
and ‘AED 2’), both drugs have to share the
plasma protein (or share the seats on the
train).
Therefore the sleeping ‘AED 1’
passengers will occupy only half of the train
whilst sleeping ‘AED 2’ passengers will
occupy the other half.
Why are drugs not always effective in
controlling seizures?
Once the drug enters the gut via the mouth or
the back passage, it then has to pass through the
walls of the gut to enter the blood stream.
There are areas in the gut where the drug is most
easily absorbed such as through the lining of the
mouth, the stomach, the small intestines or the
rectum. This is why drugs can be given either by
mouth or via the rectum.
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Sometimes, the dose of an AED is not effective in
controlling seizures. This may be because a high
portion of the drug is bound to the plasma protein
(or has hopped onto the passenger train and is
sleeping). In this case, the doctor may prescribe a
higher dose, so that more of the drug is available in
its active state.
Unfortunately, it is when the drug is active, that it
can also produce side effects.
What can the doctor do when one drug is
not effective?
If more ‘AED 2’ gets on the train, some ‘AED
1’ will be pushed out. This results in more
‘AED 1’ being in its active state - remember
that when drugs are not bound to plasma
protein (i.e. not on the train), they are in an
active state.
The doctor may add-on a second drug to control
the seizures.
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As it has already been said, in its active state,
drugs can produce side effects. Giving ‘AED 1’
as well as ‘AED 2’, actually increases the
activity of the first AED and produces side
effects. The side effects displayed are caused
by ‘AED 1’, not ‘AED 2’.
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The same principle is applied to all drugs that
are bound to plasma proteins.
Why do some people need much
lower doses of drugs than others?
Some people such as children, the elderly or
people who are seriously ill have low plasma
protein levels and are more prone to produce
side effects. In other words, there are fewer
carriages on the passenger train so less of the
drug is carried (asleep) on the train and more
of it is in its active state. In these cases, it is
necessary to start with a much lower dose of
the drug.
UNDERSTANDING
ANTI EPILEPTIC
DRUGS (AED’s)
If you are concerned about the side effects of
any drug, it is important to discuss the causes
of the side effects with your doctor or
Community Nurse before stopping the drug.
Where can I get more information about
the effects of anti-epileptic drugs?
The British Epilepsy Society has a useful
website for all aspects of epilepsy.
Information on anti-epileptic drugs and side
effects can be found at the following
address:
www.epilepsy.org.uk
Alternatively, contact your doctor
Community Nurse for information.
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or
Produced by
Fiona Rich, RNLD; BSc (Hons), MSc, Cert Ed,
Professional Diploma in Epilepsy Care.
Epilepsy Liaison Team
South Birmingham PCT
A Guide for
Parents and Carers
of people with
learning
disabilities