Selective serotonin reuptake inhibitors

Page last reviewed: 13/07/2011

Selective serotonin reuptake inhibitors (SSRIs) are medicines used to treat depression and other mood-related disorders.

SSRIs may be taken for:

  • moderate and severe depression
  • generalised anxiety disorder
  • obsessive compulsive disorder

Also, some SSRIs may be taken for:

  • the eating disorder bulimia nervosa (fluoxetine)
  • panic disorder (citalopram, escitalopram and paroxetine)
  • post-traumatic stress disorder (paroxetine and sertraline)

How they work

SSRIs boost levels of a substance called serotonin in the brain.

When serotonin is released in the brain, it helps lift mood. It is thought that people with depression release only small amounts of serotonin. The SSRIs prevent the reuptake (absorption) of serotonin back into the nerve cells.

It may take two to four weeks for an SSRI to start improving your mood. You should continue taking your SSRI even if it does not seem to work at first. Sometimes, the symptoms of depression get worse before the SSRI can have an effect. Talk to your doctor if your depression gets worse or if you have any thoughts of suicide or self-harm.

Once your depression lifts, your doctor will advise you to continue taking the SSRI for at least a further four to six months, as this reduces the chance of a relapse of your depression after you stop taking the SSRI.

Also, when you stop taking an SSRI, your doctor will advise you to reduce the dose gradually over a number of weeks or months to avoid withdrawal effects Do not stop taking an SSRI suddenly without talking to your doctor.

It is not fully understood how SSRIs help treat anxiety disorders, bulimia, obsessive compulsive disorder, panic disorders or post-traumatic stress disorder. 

Names

There are several different SSRIs. Names include:

  • citalopram (brand name Cipramil)
  • escitalopram (brand name Cipralex)
  • fluoxetine (brand name Prozac)
  • fluvoxamine (brand name Faverin)
  • paroxetine (brand name Seroxat)
  • sertraline (brand name Lustral)
Depression
Depression is when you have feelings of extreme sadness, despair or inadequacy that last for a long time.
Anxiety
Anxiety is an unpleasant feeling when you feel worried, uneasy or distressed about something that may or may not be about to happen.

Page last reviewed: 13/07/2011

When to avoid SSRIs

Selective serotonin reuptake inhibitors (SSRIs) should not be taken if you:

  • have mania (very elevated mood, sometimes with hallucinations)
  • have bipolar disease (manic depression) and you are in a manic phase
  • have previously had an allergic reaction to an SSRI

SSRIs should also be avoided if you are taking:

  • a monoamine oxidase inhibitor antidepressant such as isocarboxazid, phenelzine or tranylcypromine, or if you have taken one of these within the last two weeks
  • moclobemide, or if you have taken moclobemide within the last week
  • rasagiline or selegiline

Using SSRIs with caution

SSRIs should be taken with caution if you have a history of:

  • mania (very elevated mood, sometimes with hallucinations)
  • neuroleptic malignant syndrome (a life-threatening condition in which the body temperature rises rapidly)
  • thoughts of suicide or self-harm

SSRIs should also be taken with caution if you have:

  • angina (chest pain) or if you have had a heart attack
  • a bleeding disorder or if you are taking medicines such as warfarin that increase your risk of bleeding
  • diabetes
  • epilepsy (SSRIs should only be taken if your epilepsy is well controlled, and should be stopped if your epilepsy gets worse)
  • liver problems
  • glaucoma (increased pressure in the eye)
  • kidney problems

SSRIs should also be taken with caution if you are:

  • a young adult aged 18-25 years
  • an elderly person
  • receiving electroconvulsive therapy (ECT) for severe depression or mania

Children and adolescents

SSRIs should not be taken by children or adolescents under 18 years old to treat depression unless they are recommended by a specialist in mental health, and only with careful monitoring for side effects.

There is a higher incidence of suicide and self-harm when children or adolescents take SSRIs, particularly in the first weeks of treatment.

Only fluoxetine (Prozac) has been shown in clinical trials to be effective for the treatment of depression in this age group.

Pregnancy and breastfeeding

Some SSRIs may be taken during pregnancy, but only with caution and after weighing up the benefits to the mother against the risks to the unborn baby. In particular, the newborn baby may have withdrawal effects if the mother was taking an SSRI during the later stages of pregnancy.

Speak to your doctor if you get pregnant or are planning to get pregnant when taking an SSRI.

Some SSRIs may be taken by breastfeeding mothers. Speak to your doctor about the best choice for you.

Page last reviewed: 13/07/2011

SSRIs are usually started at a low dose, which is gradually increased over several weeks to help reduce side effects.

SSRIs take several weeks to take full effect and sometimes the symptoms of depression may worsen before the SSRI can take effect. For some people, this may include thoughts of suicide or self-harm.

SSRIs may also make you feel more anxious (worried and panicky) and may make you very restless and unable to sit or stand still.

If you experience any of these symptoms, speak to your doctor straight away.

Very common side effects

More than one person in 10 may experience the following:

  • nausea (feeling sick)
  • low sex drive, lack of orgasm and (in men) abnormal erection or ejaculation
  • withdrawal effects when stopping SSRIs (see below)

Common side effects

Up to one person in 10 may experience the following:

  • blurred vision
  • diarrhoea or constipation
  • dizziness
  • dry mouth
  • feeling agitated or shaky
  • insomnia (not sleeping well) or feeling very sleepy
  • loss of appetite
  • sweating
  • yawning

Less common side effects

Up to one person in 100 may experience the following:

  • bruising or bleeding, including vomiting blood or blood in your stools (speak to your doctor or go to hospital straight away)
  • confusion
  • extra-pyramidal disorder (lack of movement, stiffness, shaking or abnormal movements of the mouth and tongue)
  • hallucinations (seeing or hearing things that are not real)
  • being unable to pass urine (speak to your doctor or go to hospital straight away)
  • vomiting
  • weight gain

Rare side effects

Up to one person in 1,000 may experience the following:

  • a feeling of restlessness and an inability to sit or stand still (speak to your doctor)
  • convulsions (fits) or worsening of epilepsy (speak to your doctor or go to hospital straight away)
  • feeling very anxious
  • mania (very elevated mood, sometimes with hallucinations)

Very rare side effects

Up to one person in 10,000 may experience:

  • an allergic reaction, including a red and lumpy skin rash; swelling of the eyelids, face, lips or tongue; itching or breathing difficulties
  • glaucoma (an eye disease that affects vision)
  • serotonin syndrome, which is a very severe reaction that includes feeling confused or restless, sweating, shaking, shivering, hallucinations, sudden jerks of the muscles and a fast heart beat

Speak to your doctor straight away if you think you may have these symptoms.

Withdrawal effects

When you stop taking an SSRI, your doctor will advise you to reduce the dose gradually over a number of weeks or months to avoid withdrawal effects. Do not suddenly stop taking an SSRI without first talking to your doctor.

Very common withdrawal effects (affecting more than one person in 10) include:

  • feeling anxious
  • feeling dizzy or unsteady
  • headaches
  • pins and needles, burning sensations or occasionally electric-shock sensations
  • sleep disturbances (inability to sleep, nightmares, vivid dreams)

Common withdrawal effects (affecting up to one person in 10) include:

  • diarrhoea
  • feeling confused or disorientated
  • feeling emotional or irritable
  • feeling restless or agitated
  • palpitations (a fluttering or pounding heartbeat)
  • tremor (having the shakes)
  • sweating, including night sweats

Ability to drive

SSRIs may cause blurred vision, confusion or dizziness. If you are affected by any of these side effects, you should not drive.

Page last reviewed: 13/07/2011

When two or more medicines are taken at the same time, the effects of one of the medicines can be altered by the other. This is known as a drug-drug interaction. SSRIs can interact with other medicines.

Some of the more common interactions are listed below. However, this is not a complete list.

If you want to check that your medicines are safe to take with SSRIs, you can ask your doctor or pharmacist or read the patient information leaflet that comes with your medicine.

Antiplatelets

There is an increased risk of bleeding when SSRIs are taken with antiplatelets such as low-dose aspirin or clopidogrel. Speak to your doctor for advice before taking SSRIs if you take antiplatelets.

Clozapine

SSRIs can increase the level of clozapine in the blood, which increases the risk of side effects from clozapine. Speak to your doctor for advice before taking SSRIs if you take clozapine.

Duloxetine

There is an increased risk of serotonin syndrome when SSRIs are taken with duloxetine. SSRIs should not be taken with duloxetine.

Lithium

SSRIs can increase the blood level of lithium, which increases the risk of side effects from lithium. You should have regular blood tests to monitor the level of lithium in your body, especially when starting or stopping an SSRI or when changing the dose of an SSRI.

Moclobemide

There is an increased risk of serotonin syndrome when SSRIs are taken with moclobemide. SSRIs should not be taken with moclobemide or for one week after stopping moclobemide.

Monoamine oxidase inhibitor antidepressants

There is an increased risk of serotonin syndrome when SSRIs are taken with monoamine oxidase inhibitor (MAOI) antidepressants such as isocarboxazid, phenelzine or tranylcypromine.

SSRIs should not be taken with an MAOI antidepressant or for two weeks after stopping an MAOI antidepressant.

Medicines for diabetes

SSRIs may worsen the control of diabetes, which may require your dose of medicines for diabetes to be adjusted. These medicines include gliclazide, glipizide and metformin.

Non-steroidal anti-inflammatory drugs (NSAIDs)

There is an increased risk of bleeding when SSRIs are taken with non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, diclofenac or naproxen. Speak to your doctor for advice before taking SSRIs if you take NSAIDs.

Pimozide

SSRIs increase the level of pimozide in the blood, which increases your risk of side effects from pimozide. SSRIs should not be taken with pimozide.

Rasagiline and selegiline

There is an increased risk of serotonin syndrome when certain SSRIs are taken with rasagiline or selegiline.

Because of this, SSRIs should not be taken with rasagiline or selegiline and SSRIs should not be started for two weeks after stopping rasagiline or selegiline.

Also, selegiline should not be started for five weeks after stopping fluoxetine, two weeks after stopping sertraline and one week after stopping other SSRIs.

Rasagiline should not be started for five weeks after stopping fluoxetine or two weeks after starting fluvoxamine.

Sibutramine

There is an increased risk of serotonin syndrome when SSRIs are taken with sibutramine. SSRIs should not be taken with sibutramine.

St John's Wort

There is an increased risk of serotonin syndrome when SSRIs are taken with St John's Wort. SSRIs should not be taken with St John's Wort.

Tramadol

There is an increased risk of seizures (fits) and serotonin syndrome when SSRIs are taken with tramadol. Speak to your doctor for advice before taking SSRIs if you take tramadol.

Tricyclic antidepressants

SSRIs can increase the levels of some tricyclic antidepressants (including amitriptyline, clomipramine, dosulepin, imipramine or nortriptyline) in the blood. This increases the risk of side effects from tricyclic antidepressants.

You should only take an SSRI with a tricyclic antidepressant if it is recommended by a specialist in mental health and you are monitored closely for side effects.

Triptans for migraine

There is an increased risk of serotonin syndrome when SSRIs are taken with a triptan such as almotriptan, eletriptan, frovatriptan, naratriptan, rizatriptan, sumatriptan or zolmitriptan. Speak to your doctor for advice before taking SSRIs if you take triptans for migraine.

Tryptophan

There is an increased risk of agitation and nausea when SSRIs are taken with tryptophan. Speak to your doctor for advice before taking SSRIs if you take tryptophan.

Venlafaxine

There is an increased risk of serotonin syndrome when SSRIs are taken with venlafaxine. SSRIs should not be taken with venlafaxine.

Warfarin

SSRIs can enhance the effect of warfarin, which may increase your risk of bleeding. You should have regular blood tests to monitor the effect on the warfarin, especially when starting or stopping an SSRI or when changing the dose of an SSRI.

Interactions with food and alcohol

Do not drink alcohol while you are taking an SSRI. Alcohol may worsen both the symptoms of depression and any side effects from the SSRI.

There are no known interactions between SSRIs and food.

Page last reviewed: 13/07/2011

Missed dose

If you forget to take your SSRI, take that dose as soon as you remember and then continue to take your course of SSRIs as you would normally. 

However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

If you have to take two doses closer together than normal, there is an increased risk of side effects.

Check the patient information leaflet that comes with your medicine, as this will also give advice on what to do.

If you forget to take one or more doses of your SSRI, you may experience withdrawal effects. These usually stop when you take your SSRI. However, if you are concerned, speak to your GP or pharmacist

Extra doses

If you take one or more extra doses, speak to your GP

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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