How do antidepressants
work?
Antidepressants correct imbalances in the levels
of chemical messengers - neurotransmitters - in
the brain, particularly serotonin and noradrenaline.
The types of antidepressants that are available
include:
serotonin
and noradrenaline re-uptake inhibitors (SNRIs)
selective
serotonin re-uptake inhibitors (SSRIs)
serotonin
5-HT2 blockers
tricyclic
antidepressants (TCAs)
monoamine
oxidase inhibitors (MAOIs)
tetracyclic
antidepressants
noradrenaline
and specific serotonin antidepressants (NaSSAs).
SNRI antidepressants improves the levels of serotonin
and noradrenaline in the brain. In contrast, the
SSRIs and 5-HT2 blockers improve the levels of serotonin
only. Tricyclic and tetracyclic antidepressants
affect the levels of serotonin and noradrenaline
either alone or together, depending on the drug
used. MAO inhibitors work by blocking the metabolism
of serotonin and noradrenaline and increase levels
in the brain. NaSSAs also work by increasing the
levels of serotonin and noradrenaline.
Antidepressants should not be confused with sedatives,
stimulants or tranquillisers. They are not addictive.
Although antidepressant medications begin to alter
brain chemistry with the very first dose, it usually
takes 2-4 weeks before there is a marked improvement
in symptoms. It may be necessary to take antidepressants
regularly for up to 8 weeks before the full effect
occurs. Even after symptoms have improved, the medication
is usually taken for at least 6-12 months to sustain
recovery. It is important not to stop taking antidepressants
until advised by a doctor. Questions about any antidepressant
prescribed, or problems that may be related to the
medication, should be discussed with the doctor
who prescribed it.
