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Tricyclic Antidepressants:
Tell me All About Them
Tricyclic Antidepressant
Medication : An Overview
 The tricyclic antidepressants
were accidentally discovered in the 1950s. Researchers studying the use of a new
drug, imipramine for schizophrenia, found that rather than being
effective for schizophrenia, it actually had the effect of relieving depression
in many people. The new drug later named Tofranil, and the related
compounds, became known as tricyclic antidepressants because of the shape of
their molecular structure.
After several hundred studies,
it has been found that depressed patients taking tricyclic antidepressants have
improved much more than similar patients taking placebos. However, it must be
noted that the antidepressants usually must be taken for at least 10 days before
such improvements may begin. Approximately 60% to 65% of patients taking tricyclic antidepressants seem to be helped by them.
The relapse rate after
discontinuing the use of tricyclic antidepressants is quite large. Many studies
have found that when depressed people stop taking tricyclics immediately upon
relief of symptoms, they run a risk of as much as 50% of relapsing within a
year. However, if they continue taking these drugs at full dosage for five
months or so after being free of the depressive symptoms, a practice called
"continuation therapy", the risks for relapse are reduced significantly.
Researchers also found that when these antidepressants are taken at full dosage
for three or more years after the initial improvement of symptoms, a practice
called "maintenance therapy", the risk of relapse is reduced even more. As a
result of this research, many clinicians are known to keep patients on these
antidepressants indefinitely.
Researchers have concluded that
tricyclic antidepressants reduce depression by acting on neurotransmitter
"reuptake" mechanisms. Messages are carried from one neuron across a synaptic
space to a receiving neuron by a neurotransmitter, a chemical released from the
nerve ending of the sending neuron. There is however, a complication to this
process. While the nerve ending is releasing neurotransmitter, a pump-like
mechanism in the sending neuron is also trying to recapture the extra
neurotransmitter that has been released. The purpose of this process is to
prevent the neurotransmitter from remaining in it space between the two neurons
for too long a period of time, and repeatedly stimulating the receiving neuron.
It is believed that this pump-like reuptake mechanism is actually too successful
in some people, reducing norepinephrine or serotonin activity too much. The
reduced activity of these neurotransmitters may result in clinical depression.
Apparently tricyclic antidepressants block this reuptake process, thus
increasing the level of neurotransmitter activity.
If tricyclic antidepressants
act immediately to increase norepinephrine and serotonin activity and that
efficiency, why do the symptoms of depression continue for 10 or more days after
drug therapy begins? There is now growing evidence that when tricyclic
antidepressants are ingested, they initially slow down the activity in
the neurons that use norepinephrine and serotonin. The reuptake mechanisms of
these cells are immediately corrected, thus allowing more efficient transmission
of the neurotransmitters, but then responding to the change by releasing smaller
amounts of these nuerotransmitters. After a week or two, the neurons finally
adapt to the tricyclic antidepressants and go back to releasing normal amounts
of the neurotransmitters. Now the corrections in the reuptake mechanisms begin
to have the desired effect in that the neurotransmitters reach the receptor
neurons in greater numbers, hence triggering an increase in the level of firing
from the sending neuron and producing a decrease in depression.
Tricyclic antidepressants are
prescribed much more often than the MAO inhibitors. They are much less
dangerous than the MAOI's, and do not require restrictions of a persons diet.
Also persons taking tricyclic antidepressants typically show higher rates of
improvement than those taking MAO inhibitors. However, there are some
individuals that respond better to the MAO inhibitors than either tricyclic
antidepressants or the newer drugs described as second-generation
antidepressants or selective serotonin reuptake inhibitors (SSRI’s) which seem
to be the most popular.
Information
from Ronald J. Comer’s Abnormal Psychology
Additional
Information and webpage by
Paul Susic
MA
Licensed Psychologist Ph.D. Candidate
(Health and Geriatric Psychologist)
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