  
|  |
|
| Selective serotonin re-uptake inhibitors |
|
|
Written by Dr Adrian Lloyd, lecturer and honorary specialist registrar in psychiatry
|
Selective serotonin re-uptake inhibitors (SSRIs) is the name
given to a group of antidepressant medicines. When used in reference to
medicines, the term 'group' means that each of the drugs in the group is
broadly similar to the others in the way that it works.
Differences between medicines within a group are usually fairly
small, for example they may differ in dosage frequency or in their particular
spectrum of side effects.
There are a number of SSRIs that are frequently used to treat
depression. There is detailed information about these individual medicines in
the factsheets linked below:
-
citalopram (eg Cipramil)
-
escitalopram (Cipralex)
-
fluoxetine (eg Prozac)
-
fluvoxamine (eg Faverin)
-
paroxetine (eg Seroxat)
-
sertraline (eg Lustral)
What is the difference between SSRIs and other antidepressants?
As far as their effectiveness in treating depression goes, all
antidepressants are about as good as each other. There is little to choose in
this respect between any of the SSRIs, or for that matter between the SSRIs and
other types of antidepressant.
Generally, about two thirds of people with depression who take
any one type of antidepressant will find that it improves the way they
feel.
If one medicine doesn't work, it is well worth trying another
group of antidepressants such as
tricyclic antidepressants (TCAs) or
monoamine oxidase inhibitors (MAOIs),
rather than another antidepressant from the same group.
What gives SSRIs their name and makes them a unique group is the
way that they work.
-
Serotonin is one of several chemicals called neurotransmitters
that pass messages between nerve cells that are involved in depression.
-
Each nerve cell generally uses one of these chemicals to pass
on messages to adjacent nerve cells.
-
If there is not enough serotonin released by the first nerve
cell, it won't be able to cause the next one to 'fire' - the message won't get
through. This is one of the changes that appears to be important in causing
depression.
-
The nerve cells normally recycle serotonin by soaking it back
up again. The SSRIs work by stopping (inhibiting) this re-uptake of serotonin.
As the serotonin is not soaked up again, more will be present to pass on
messages to nerve cells nearby.
-
SSRIs work selectively on serotonin - they don't stop the other
types of neurotransmitter chemical being soaked up by the nerve cells.
For someone taking these antidepressants, the most significant
differences between them are the effects that they have in addition to treating
depression. Some of these are helpful and others are unwanted side effects.
How can you tell if an SSRI will work?
The straight answer to this question is that until an
antidepressant is tried it is impossible to know whether it is the right one
for any individual, and it takes a number of weeks (two to eight) to know
whether it is going to work.
The first medicine to try is often decided on the grounds of its
other effects rather than its antidepressant properties (since all
antidepressants are equally effective). Some of these considerations are listed
below.
-
Is it sedative?
-
Is it more alerting?
-
Will it help anxiety as well? (Anxiety often goes hand-in-hand
with depression.)
-
Will it help another disorder, eg obsessive compulsive
disorder, that coexists with the depression?
-
Does it mix well with other medicines that a person is taking?
-
Is it okay if the person has other illnesses?
-
Has the person taken it before to good effect?
To make the best initial choice, the doctor needs to know
exactly how a person is affected by depression. Some of these other effects may
be very helpful in one person, but a problematic side effect in another:
sedation is useful in someone whose sleep is disrupted, but not for someone who
is sleeping too much.
SSRIs are different to the tricyclic antidepressants - the other
main group of drugs that are frequently used as a first option for treating
depression. SSRIs are:
-
less sedating.
-
better for people with heart problems.
-
helpful in people who feel slowed up by their depression.
-
helpful for people with marked anxiety, especially obsessive
compulsive symptoms, along with their depression.
-
less likely to cause abnormally high mood when used to treat
the depressive phase of manic depression.
Who will prescribe them?
GPs often prescribe SSRIs for depression, as do psychiatrists if
they have been asked by a person's GP to give further help in treating
depression.
How long do they take to work?
As with all antidepressants, the SSRIs need some time (two to
eight weeks) to start having an effect, so you may not feel better immediately
when you start treatment with one. It is vitally important to keep taking them,
even if they don't seem to make much difference in the beginning.
How long will I have to take them for?
SSRIs 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 SSRIs 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 dizziness, numbness and
tingling sensations, digestive disturbances (particularly nausea and vomiting),
headache, sweating, anxiety and sleep disturbances, including vivid dreams. It
seems that paroxetine is more commonly associated with withdrawal symptoms than
other SSRIs, and fluoxetine least commonly.
Withdrawal symptoms can be minimised or avoided entirely if the
dose of the SSRI is gradually decreased over a period of a few weeks. Your
doctor will help you do this.
Withdrawal symptoms can sometimes happen if you miss a dose of
certain SSRIs, for example paroxetine. For this reason it is important to
follow the dosing instructions given by your doctor.
What are the side effects?
Many people take these medicines with little or no side effects,
and when they do occur they are usually mild and tend to disappear after one to
two weeks.
Occasionally, side effects may be bad enough to warrant stopping
a particular drug, but even in this case it is often possible to try another
SSRI or to change to a different type of antidepressant.
Another strategy is to try the same drug, but to start off with
a lower dose than usual and to increase it very gradually.
The side effects that the SSRIs tend to cause most commonly
include:
-
nausea
-
diarrhoea
-
constipation
-
loss of appetite (sometimes increased appetite and weight
gain)
-
dry mouth
-
headache
-
insomnia (sometimes drowsiness)
-
tremor (shakiness)
-
sweating
-
light-headedness
-
problems with sexual arousal and delayed orgasm.
Sometimes in the first few weeks of treatment SSRIs can make you
feel agitated, restless, or like you can’t sit or stand still. If you get this
or any other distressing effect, you should let your doctor know.
SSRIs and anxiety
SSRIs can cause worsening of anxiety right at the start of
treatment, even though they are prescribed to treat anxiety.
This only lasts for a brief period and usually settles down. The
anxiety then starts to improve. If anxiety does briefly get worse at the start
of treatment with an SSRI, this can be a good sign that the depression and
anxiety will ultimately respond well to the treatment.
This side effect can be reduced by starting the SSRI at a lower
dose than would normally be used and building it up slowly.
What should I do if I experience side effects with an
SSRI?
If these 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.
SSRIs and suicidal ideas
A lot of publicity has been given to a few reports of people
becoming suddenly suicidal while taking Prozac (fluoxetine) or Seroxat
(paroxetine).
As a result, this has been looked at very carefully in all the
SSRIs by the Medicines and Healthcare Regulatory Authority (MHRA); the agency
of the Department of Health that ensures medicines in the UK meet appropriate
standards of safety, quality and effectiveness.
After studying all the available research, the MHRA decided in
December 2003 that SSRIs (with the exception of fluoxetine) should not be
prescribed for children under 18 because they may more do more harm than good
in this age group.
In December 2004, the MHRA found that evidence linking SSRIs to
suicidal behaviour in adults is weak and that the benefits of these medicines
in adults generally outweigh any risks.
The SSRIs are proven to be very effective treatments for
depression and most likely, it is the depressive illness itself that leads to
suicidal feelings.However, as a precautionary measure, young adults over the
age of 18 should be closely monitored when they start an SSRI, as suicidal
behaviour in general is more common in this age group than in older
adults.
It is important to tell your doctor immediately if you think
your depression has got worse after starting treatment for depression. If you
have any distressing thoughts or feelings at any time while taking an
antidepressant, particularly in the first few weeks and after any dose changes,
then you should also contact your doctor.
SSRIs in manic depression (bipolar affective disorder)
SSRIs are less likely than other antidepressants to cause
abnormally high mood (mania or hypomania) in
manic depression.
However, they can still cause high mood.
Usually, a person who needs an SSRI to treat the depressive
phase of bipolar disorder should stop taking it once the depression has gone.
(This is quite different to the advice given for the more common type of
depression, ie which is not associated with periods of elevated mood, in which
the medicine should be continued for six months after the depression has gone.)
What are the other illnesses that SSRIs can be used
for?
Lastly, there are other reasons that someone might be
prescribed an SSRI. Although these drugs are called antidepressants, some can
also treat:
-
panic disorder
-
generalised anxiety disorder
-
obsessive compulsive disorder
-
bulimia nervosa
-
social phobia
-
post traumatic stress disorder.
|
|
|
Last updated 27.03.2007
|
 |
|
|
 |
| |      |
|
