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| Tricyclic antidepressants |
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Written by Helen Marshall, pharmacist
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Tricyclic antidepressants (TCAs) are one of the oldest classes
of antidepressants and are still used extensively. Before the introduction of
selective serotonin reputake inhibitors
(SSRIs), TCAs were the standard treatment for depression. However, they
are associated with more side effects than the SSRIs, and are now more likely
to be reserved for cases when SSRIs are ineffective or inappropriate.
How do TCAs work?
Within the brain, there are many naturally occurring chemical
messengers called neurotransmitters. These chemicals are involved in
controlling or regulating bodily functions. Two of these chemicals,
noradrenaline and serotonin, are involved in the control and regulation of
mood.
When depression occurs, there may be a decreased amount of these
two chemicals released from nerve cells in the brain. When these chemicals are
released from nerve cells they act to lighten mood. When they are reabsorbed
into the nerve cells, they no longer have an effect on mood.
TCAs work by preventing this reabsorption of noradrenaline and
serotonin back into the nerve cells. This prolongs the mood-lightening effect
of any released noradrenaline and serotonin and in this way helps to relieve
depression.
How long do TCAs take to work?
TCAs can take a while to have an effect so you may not feel
better immediately when you start treatment with one. You may experience an
effect on your mood within two weeks, however, the full benefits of treatment
with TCAs may not occur for a further two to four weeks. If you feel your
depression has got worse, or if you have any distressing thoughts or feelings
in these first few weeks, then you should talk to your doctor.
How long will I have to take them for?
TCAs usually help mood improve over a number of weeks or months.
Even when things seem back to normal, you should keep taking them for a further
six months to minimise the chances of the depression coming back.
Are they addictive?
No. It is possible for TCAs to produce unpleasant withdrawal
symptoms (sometimes called a discontinuation syndrome) when they are stopped.
But this is temporary, does not involve a craving for the medication, and can
usually be avoided if the drug is tapered off rather than stopped suddenly.
This is not addiction.
Withdrawal symptoms may include insomnia and increased
dreaming, and flu-like symptoms such as headache, sweating, chills, nausea or
muscular aches. It seems that amitriptyline and imipramine are more commonly
associated with withdrawal symptoms than other TCAs. Withdrawal symptoms can
sometimes occur if you miss a dose of the antidepressant, which is why it is
important to take them as directed by your doctor.
When stopping treatment withdrawal symptoms can be minimised or
avoided entirely if the dose of the TCA is gradually decreased over a period of
a few weeks. Your doctor will help you do this.
Which one is best for me?
All antidepressants are equally effective so the choice of TCA
depends on a number of factors relating to other effects of the medicine, other
diseases a person has, or other medicines they may be taking.
TCAs should
generally not be used if you have a heart problem, are breastfeeding, pregnant
or have a liver problem (see the individual medicine factsheets linked below
for information on specific cautions).
Some TCAs, eg amitriptyline, cause more
drowsiness than others and are useful for treating depression in people who are
also anxious and agitated. TCAs that cause less drowsiness, eg imipramine and
lofepramine, are useful for withdrawn and lethargic people. Lofepramine is also
often used to treat depression in the elderly, as it has less potential for
side effects on the heart than the other tricyclics. So which is best for you
depends on a combination of your medical history and the characteristics of the
individual medicines.
What are the side effects?
The most common side effects experienced with TCAs include
constipation, difficulty in urinating, blurred vision, dry mouth, weight gain,
sexual dysfunction and drowsiness. TCAs tend to cause more troubling side
effects than some of the newer antidepressants, such as SSRIs.
What should I do if I experience side effects with a TCA?
If side effects are only slight and you have just started to
take the medication, they will usually settle down on their own after a week or
two. If they are very problematic, or are not settling down at all, you need to
discuss this with your doctor to decide how to handle the problem. There are
various options, such as reducing the dosage or changing to another
antidepressant, and the benefits of treating the depression have to be weighed
against the side effects of the treatment.
| Tricyclic
antidepressants |
| Allegron (nortriptyline)
| Lomont (lofepramine)
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| Amitriptyline | Prepadine (dosulepin) |
| Anafranil
(clomipramine) | Prothiaden
(dosulepin) |
| Anafranil SR
(clomipramine) | Sinepin (doxepin) |
| Imipramine | Surmontil
(trimipramine) |
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Last updated 14.02.2007
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