SSRIs are medicines that boost serotonin. They can be used to help treat some of the symptoms of:

• Anxiety (GAD or Generalised Anxiety Disorder) (escitalopram and paroxetine are licensed)

• Depression

• Eating disorders, particularly fluoxetine for bulimia nervosa

• OCD (Obsessive Compulsive Disorder)

• PTSD (Post-Traumatic Stress Disorder)

• Social anxiety

SSRIs can also sometimes be used to help the symptoms of:

• Bipolar depression

• Dementia, where depression is making the symptoms worse

• Panic disorder

• Seasonal Affective Disorder

SSRIs are also sometimes used for pre-menstrual syndrome and agoraphobia.

There are other treatments for the conditions above. The main ones are included in the section on each of the conditions above.

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This will rather depend on what you are taking it for. To help you choose, click on the links for the main options (self-help and help from others), the main medicines, and a handy chart comparing the main medicines:

• Anxiety - main options, main medicines and handy chart
• Bipolar depression - main options, main medicines and handy chart
• Dementia - main options, main medicines and handy chart
• Depression - main options, main medicines and handy chart
• Eating disorders - main options, main medicines
• OCD - main options, main medicines and handy chart
• Panic disorder - main options, main medicines and handy chart
• PTSD - main options, main medicines and handy chart
• Seasonal Affective Disorder - main options, main medicines and handy chart
• Social anxiety - main options, main medicines and handy chart

The main options are included in the section on each of the conditions above.

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The brain has many naturally occurring chemical messengers. One of these is called serotonin (sometimes called 5-HT) and is important in the areas of the brain that control mood and thinking. It is known that this serotonin is not as effective or active as normal in the brain when someone is feeling depressed. The SSRI antidepressants (e.g. escitalopram, citalopram, fluoxetine, paroxetine, sertraline) increase the amount of this serotonin chemical messenger in the brain. This can help correct the lack of action of serotonin and help to improve mood.

An SSRI is a Selective Serotonin Reuptake Inhibitor and blocks the reuptake of serotonin. So, the next time an impulse comes along, there is more transmitter, a stronger message is passed, and activity in that part of the brain is increased. 

To help understand this better you may find it helpful to read the answers to the following questions:

• How do medicines work in the brain?

• What happens when transmitter activity is low?

• How do SSRIs work in detail?

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We know that too little serotonin activity in the brain can cause the symptoms many conditions e.g. depression, general anxiety, social anxiety, obsessive thoughts, post-traumatic stress disorder, panic, pre-menstrual syndrome and agoraphobia. If this is true, then boosting serotonin these should help to reduce the symptoms. One way of doing this is to block the reuptake (recycling) of transmitter. This is just what an SSRI (e.g. escitalopram, citalopram, fluoxetine, paroxetine, sertraline) does. An SSRI is a Selective Serotonin Reuptake Inhibitor and blocks the reuptake of serotonin. So, the next time an impulse comes along, there is more transmitter, a stronger message is passed, and activity in that part of the brain is increased.

1. A brain cell decides to send a message to another cell.
2. The electrical impulse is sent from the brain cell down one of the nerve fibres.
3. This message arrives and the transmitter is released. But an SSRI is also hanging around.
4. The transmitters hit the receptor on the other side.
5. The message that is passed is definitely less effective, causing the symptoms you are getting e.g. low mood.
6. The transmitter is either broken or recycled. However, the SSRI blocks the reuptake of serotonin back into the nerve ending. Although a bit extra may be broken down by the enzyme, the end result is that there is some transmitter hanging around in the gap (synaptic cleft). Not enough to trigger another message though.
The next impulse comes down the nerve fibre.
As it arrives, transmitter is released as usual.
However, the amount that is released adds to the lot that is still hanging around from the last message or impulse.
The net result is that the message passed is either stronger or more easily passed than the previous one. So, if lack of messages or not strong enough messages causes a drop in mood or other symptoms, boosting these messages will help correct this, raising mood.

The important thing to remember is that SSRI antidepressants probably mainly work by correcting the effect of having too little transmitter. They are NOT STIMULANTS. They have a much more specific way of working than stimulating you.

As the author of this once saw painted on the end of a building “depression is a defect in chemicals not character”.

As we’ve just seen, SSRIs mainly block the reuptake of just serotonin. This is why they are called the SSRIs ie. Selective Serotonin Reuptake Inhibitors. Too much serotonin in some other parts of the brain can make you feel sick, less hungry and get headaches or migraines.

In much the same way as antidepressants take a week or so to start working, most of the side effects tend to wear off over a week or so as the brain gets used to them. Starting at a lower dose for a few days also helps.

Similarly, taking a medicine away from the brain quickly is a bit unfair to it. So, if you are stopping, it is best to reduce the dose for a week or so if you can before stopping to allow the brain to get used to it. As someone once said to me, it’s a bit like stopping a car quickly without your seatbelt on. You can do it, but it hurts. It’s better to slow down gently. Wise words indeed.

So, this is how we think SSRIs work as antidepressants. It is not quite as simple as this, but this is what we currently think is the main way in which they work.

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Tablets and capsules:
Tablets and capsules should be swallowed with at least half a glass of water whilst you are sitting or standing. This is to make sure that they reach the stomach and do not stick in your throat.
Liquids:
Your pharmacist should give you a medicine spoon or oral syringe. Use it carefully to make sure you measure the correct amount. Ask your pharmacist for a medicine spoon if you do not have one.

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This may depend on what you are taking it for. Click the link below for the answer for that condition:

• Anxiety (GAD or Generalised Anxiety Disorder)
• Bipolar depression
• Dementia
• Depression
• Eating disorders
• Obsessive Compulsive Disorder
• Panic disorder
• PTSD (Post-Traumatic Stress Disorder
• Seasonal Affective Disorder
• Social anxiety

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Take your SSRI as directed on the medicine label. If you are told to take your dose once a day this is best in the morning. If you take it at night it can affect your sleep and you will not sleep as well. If you feel sick when you first start taking your SSRI, this should only last for a few days, but it can be helped by taking your dose with or after food. Also, taking it with breakfast may make it easier to remember as there is no problem about taking any SSRI with or after food. They are not sleeping tablets.

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This will depend on what you are taking it for. It may also depend on how unwell you have been or how severe the symptoms have been, as people respond differently. Click on the link below for the answer for that condition:

• Anxiety (GAD or Generalised Anxiety Disorder)
• Bipolar depression
• Dementia
• Depression
• Eating disorders
• Obsessive Compulsive Disorder
• Panic disorder
• PTSD (Post-Traumatic Stress Disorder)
• Seasonal Affective Disorder
• Social anxiety

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SSRIs are not addictive, but if you have taken them for eight weeks or more you may experience some mild "discontinuation" effects if you stop them suddenly. This does not mean that the SSRIs are addictive. For a drug to be addictive or produce dependence, then it must have a number of characteristics:

• should produce craving for the drug when the last dose "wears off"

• there should be a "reward" (e.g. a good feeling) from taking the drug

• should produce tolerance ie you need more drug to get the same effect

• should produce withdrawal symptoms specific to that drug.

These characteristics come from the World Health Organisation. SSRIs have none of these. If stopped suddenly, may produce some "discontinuation" symptoms but these are more of an "adjustment" reaction from sudden removal of a drug rather than withdrawal. These symptoms seem to happen with paroxetine more than any of the others.

Click here to read a bit more about this, where you can find our thoughts on this knotty problem.

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Start again as soon as you remember that day, then go on as before. Do not try to catch up by taking two or more doses at once as you may get more side-effects. Missing a dose every now and again is probably not a big problem (e,g, no more than once a week). It is best not to take an SSRI too late in the day as it may affect your sleep.

If you have problems remembering your doses (as very many people do) ask your pharmacist, doctor or nurse about this. There are some special packs, boxes and devices which can be used to help you remember. You can try leaving the pack somewhere you will see it each morning e.g. in the bathroom, kitchen, in a car etc.

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It is unwise to stop taking them suddenly, even if you feel better. Two things could happen. Firstly, your symptoms can return if treatment is stopped too early (see "How long will I need to keep taking them for?"). Secondly, you might also experience some mild "discontinuation" symptoms (see also above). At worst, these could include dizziness, vertigo/light-headedness, nausea fatigue, headache, "electric shocks in the head", insomnia, abdominal cramps, chills increased dreaming, agitation and anxiety. They can start shortly after stopping or reducing doses, are usually short lived, will go if the antidepressant is started again and can even occur with missed doses. These effects have been reported for all the SSRIs, but it seems that they occur more often with paroxetine than the others.

If you get these discontinuation symptoms, you have a number of options:

• If they are not severe, you can wait for the symptoms to go - they usually only last for a few days or weeks

• Ask for something to help your symptoms in the short-term e.g. a sedative or sleeping tablet

• Start the medication again (the symptoms should go) and then try reducing the dose more slowly over a longer time e.g. reduce the dose by about a quarter (25%) every 4-6 weeks. Another system that works for some people is to use the syrup; everytime you take a dose, add some diluent (e.g. syrup or water) and then the syrup gradually (rather than suddenly) gets more and more dilute.

• Switch to another antidepressant - this sometimes helps e.g. fluoxetine has a long "half-life" and is easier to stop than is e.g. paroxetine

When the time comes your doctor should withdraw the SSRI slowly e.g. by reducing the dose gradually every few weeks. You should discuss this with your doctor. If you are stopping your SSRI and would like some more advice, you can click the links below for in-depth help for each individual SSRI:

• Citalopram

• Escitalopram

• Fluoxetine

• Paroxetine

• Sertraline

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The table below will show you some of the main side effects you might get from an SSRI.

Do not be worried by this list of side effects. Some people get no side effects at all and others may get some effects that are not listed in this table. Side effects tend to be worse with higher doses. Starting with a lower dose sometimes helps. If you think you might have a side effect to your medicine, you should discuss this with your doctor, nurse of pharmacist. You should also see the manufacturer's information leaflet.

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The SSRIs may make you feel a little drowsy or sleepy to start with, although this effect is less than with most other similar medicines. You should not drive (see below) or operate machinery until you know how they affect you. You should be careful as they may affect your reaction times or reflexes. They are not, however, sleeping tablets, and they may make you sleep less well if you take them at night.

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Fluoxetine ("Prozac") may cause you to lose weight when you first start taking it. You tend to lose more weight the heavier you are so this "side effect" is not usually one which people complain about! The other medicines in this group tend to have less of an effect on body weight. If, however, you do start to have problems with your weight tell your doctor next time you meet as he or she can arrange for you to see a dietician for advice. It may be that in the long term (ie several years), it may be possible that you might gain a little weight.

Click here for a few tips on how to help you feel less hungry and lose weight.

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Drugs can affect desire (libido), arousal (erection) and orgasmic ability. The SSRIs are know to effect all three stages in some people. Delayed orgasm is fairly common (indeed some of the SSRIs are now used to help treat premature ejaculation). If this does seem to have happened, you should discuss this with your doctor, as a change in dose, when you take the dose or a change in your medication may help reduce any problem. Sometimes taking another medicine (e.g. mirtazapine or bupropion) can help some people. The SSRIs can also have an affect on the other stages so discuss this with your doctor if you think it is a problem. However, two studies have shown that having depression was more likely to affect your sex-life than an SSRI ^{(eg Lanza di Scalea 2009)}.

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You should have no problem with any foods or drinks, other than alcohol (see separate question). Taking an SSRI after food can help reduce the feelings of sickness some people get when they start taking an SSRI.

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Whether or not it is safe to drink alcohol with any medicine will depend on:

• How much you have to drink e.g. the amount and over how long
• What you then try to do (e.g. sleep or drive)
• If you have any other conditions e.g. asthma or a chest infection (as alcohol can make it harder to breathe), epilepsy
• If you are taking any other medicines

Alcohol reaches all parts of the brain and can affect many things e.g. thinking, reactions and breathing. Alcohol can also boost the effect of GABA (the brain's main calming chemical messenger).

Alcohol in moderation should be OK while taking an SSRI, although it might make you feel more sleepy. If this happens, you would need to take extra care if you need to operate machinery and you must seek advice on this. Also, the effects of alcohol can be increased if it is taken while you are taking fluvoxamine ("Faverin").

It is not safe to drive after drinking alcohol, with or without an SSRI. Some countries allow driving after a small amount of alcohol but others have a zero tolerance. The UK has the highest limit in Europe, France lower, Scandanavia even lower and zero in some Eastern European countries. It is not possible to say what blood level you might have from a drink so it is safest not to drink if you know you may have to drive. It is taken as a very serious offence in most countries. You should see National Guidelines, laws and regulations in the country in which you are driving.

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The SSRIs have some interactions with other medicines:

• Fluoxetine or paroxetine can sometimes increase the effects of some beta-blockers (e.g. propranolol, atenolol), valproate or carbamazepine (possibly), warfarin, tricyclics (e.g. dosulepin/dothiepin, imipramine, lofepramine), some antipsychotics (clozapine, risperidone, paliperidone, zuclopenthixol) or atomoxetine
• The effects of fluoxetine and paroxetine can sometimes be increased by terbinafine
• Sertraline has almost no interactions although should be used carefully with clozapine
• Citalopram also has very few interactions with other medicines. However, higher doses might cause a slight change in heart beat (making the QT interval longer) and so you have to be really careful taking citalopram with any medicines that might also cause the QT interval to be longer. These can include e.g. some antibiotics (e.g. azithromycin, clarithromycin, erythromycin, and metronidazole if taken with alcohol), some antifungals (e.g. fluconazole and ketoconazole), some antimalarials (e.g. chloroquine, mefloquine), some antiarrhythmics (e.g. disopyramide, quinidine, amiodarone and sotalol), some other antidepressants (e.g. amitriptyline, clomipramine, dosulepin, doxepin, imipramine), some antipsychotics (e.g. risperidone, fluphenazine, haloperidol, clozapine) and methadone.
• Fluvoxamine can sometimes increase the effect of caffeine, ciclosporin, lansoprazole, theophylline, clozapine, warfarin, agomelatine, melatonin, quetiapine, mirtazapine or methadone.
• Paroxetine can reduce the effect of tamoxifen (used for breast cancer) although this doesn't seem to happen with the other SSRIs ^{(Kelly, 2010)}

Particularly in people over 80, SSRIs should be taken with care if you are also taking an NSAID (used for arthritis or pain, e.g. ibuprofen, naproxen, diclofenac, ketoprofen, mefenamic acid), as this can cause stomach bleeding in a few people.

Any medicines that boost serotonin should only be used together with care as this can cause "serotonin syndrome" (which causes a 'flu-like set of symptoms, but can be more serious) e.g. any combination of SSRIs, trazodone, tramadol, linezolid, venlafaxine/desvenlafaxine, duloxetine, MAOIs (e.g. phenelzine, isocarboxazid, tranylcypromine), moclobemide, St. John’s wort, tryptophan or some triptans (e.g. sumatriptan, zolmitriptan, rizatriptan, almotriptan; used for migraine).

As someone who gets migraines I can point out there is actually no evidence for a serious problem (e.g. serotonin syndrome) with SSRIs and triptans (such as sumatriptan, naritriptan, almotriptan) for migraines (Gillman, 2010; Evans 2010). However, many many people seem to be stopped from having these wonder drugs for migraines because there is an official warning. So, the risk appears very low, although some care would be a good idea.

This does not necessarily mean that this will happen in everyone or that some of these medicines can not be used together. It is just that you may need to follow your doctor’s instructions very carefully. There are many other possible drug interactions (e.g. you can try an external on-line drug interactions checker, although this is nothing to do with our site).

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You should have no problems with "The Pill" and the SSRIs. However, if you get diarrhoea ("the runs") or are sick this might reduce the amount of "The Pill" that goes into your body. This would make it less effective.

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In the UK, Levonelle one step® is available and is usually known as 'the morning after pill'. It is taken to reduce the chances of becoming pregnant after unprotected sex or failure of a contraceptive method. In fact "Emergency Contraception" is the better term because it can be taken up to 72 hours (3 days) afterwards. It can be bought over-the-counter without a prescription from pharmacies. EllaOne® tablets (which may work up to 5 days afterwards) and a coil (Intra-uterine device) can also be used but must be prescribed by a Doctor.

If you are taking an SSRI, the usual dose should work if you follow the instructions carefully.

N.B. We accept that for religious, cultural or ethical reasons some people do not approve of, or agree with, the use of the "Morning After" pill. However, we have answered the question because it is one of the most often asked of NHS Direct in UK, and they suggested we include it.

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It is important to consider that there will be a risk to you and your child from taking a medicine during pregnancy but also a possible risk from stopping the medicine e.g. getting ill again. Unfortunately, no decision is risk-free. It will be for you to decide which is the least risk. All we can do here is to help you understand some of the issues, so you can make an informed decision. For your information, major malformations occur "spontaneously" in about 2-4% of all pregnancies, even if no drugs are taken. The main problem with medicines is termed "teratogenicity" i.e. a medicine causing a malformation in the unborn child. A medicine causing teratogenicity is called a "teratogen". Since a baby has completed it's main development between days 17 and 60 of the pregnancy (the so-called "first trimester") these first 2-16 weeks are the main concern. After that, there may be other problems e.g. some medicines may cause slower growth. The infant may also be affected after birth e.g. withdrawal effects are possible with some drugs.

If possible, the best option is to plan in advance. If you think you could become pregnant, discuss this with your doctor and it may be possible to switch to medicines thought to carry least risk, and take other risk-reducing steps e.g. adjusting doses, taking vitamin supplements etc. If you have just discovered you are pregnant, don't panic, but seek advice from your GP within the next few days if possible. He or she may also want to refer you on to someone with more specialist knowledge of your medicine.

Very few medicines have been shown to be completely safe in pregnancy and so no manufacturer or advisor can ever say any medicine is safe. They will usually advise not to take a medicine during pregnancy, unless the benefit is much greater than the risk. In the UK, there is the NTIS (National Teratology Information Service) who offer individual risk assessments. However, their advice should always be used to help you and your doctor decide what is the risk to you and your baby. There is a risk from taking the medicine and a risk should you stop a medicine e.g. you might become ill again and need to go back on the medication again. The advice offered here is just that i.e. advice, but may give you some idea about the possible risks and what (at the time of writing) is known through the medical press.

It may be helpful to know that in the USA, the FDA (Food and Drug Administration) classifies medicines in pregnancy in five groups:
A = Studies show no risk, so harm to the unborn child appears only a remote possibility
B = Animal and human studies indicate a lack of risk but are not fully conclusive
C = Animal studies indicate a risk but there is no safety data in humans
D = a definite risk exists but the benefit may outweigh the risk in some people
X = the risk outweighs any possible benefit

The SSRIs are classified as "C" or "D" (fluoxetine, sertraline, citalopram and fluvoxamine are "C", paroxetine is "D"). The SSRIs are not thought to be teratogenic in animals, and most human safety data is for fluoxetine.

Some "discontinuation" effects (such as increased breathing rate and jitteriness) have been seen in a few infants for a couple of days after birth in mothers taking paroxetine, so it may be wise to reduce the dose a little before your due date. Fluoxetine is the most widely studied SSRI in pregnancy. Information on over 2000 pregnancies indicates that the risk of "spontaneous abortion" may be slightly higher than normal but that the number of abnormalities is the same as the general population and so fluoxetine did not appear to be a major risk.  

Fluoxetine and paroxetine may have a slight increase in the chance of the baby having a "congenital cardiac defect". This means there might be a problem with the heart structure. This may be a class effect (i.e. happens with all the SSRIs) but there is not enough information about the other SSRIs to be sure. Talk to your doctor about the risks and benefits of an SSRI if you are pregnant, or could be pregnant. If you find out you are pregnant while taking paroxetine, don't stop immediately, but rather go to see your doctor as soon as possible. To put this another way, the risk of your baby having a heart problem is possibly:

• about 1% (1 in 100) if you are not taking fluoxetine or paroxetine
• about 1.4% (1 in 70) if you are taking fluoxetine or paroxetine

SSRIs might make breast-feeding a little more difficult to get started ^{(Marshall 2010)}.

A recent study has shown no evidence of any short or long-term effects on intelligence and language development, although there was a slight reduction in the length of pregnancy (by about 6 days). You should, however, still seek personal advice from your GP, who may then if necessary seek further specialist advice. Sertraline and citalopram seem to have no known problems.

Finally, there is a slight risk (1 in 100 chance) of PPHN (Persistent Pulmonary Hypertension in the Newborn) if an SSRI is taken after week 20 of pregnancy. As this can cause long-term for your baby problems you should talk to your doctor about this.

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You may feel a bit drowsy at first when taking any of the SSRIs. Until this wears off, or you know how your SSRI affects you, do not drive or operate machinery. You should be careful as it may affect your reaction times.

If you are taking any medicines, the rules about driving will depend on the country you’re driving in. Click on the links below for advice:

• Medicines and driving in the UK (England, Scotland, Northern Ireland and Wales)

• Medicines and driving in the Republic of Ireland

General advice on driving safely

If you want to drive, you should take sensible steps to reduce any risk. These could include:

• Avoid driving when you are tired or ill
• Do not drive after having any alcohol as this can make any drowsiness worse (a third of all fatal road traffic incidents involve alcohol-dependent drivers)
• Avoid driving at night, dusk or in bad weather
• Avoid motorways, dual carriageways and the rush hour
• Give yourself plenty of time. Don’t rush
• Be extra careful if you have not slept well the previous night

As some medicines can affect your driving, be extra careful:

• If starting a new medicine
• After a change in dose (especially an increase)
• If you are on a high dose or seem very sensitive to side effects
• If you are taking any medicines for other symptoms e.g. antihistamines for hay fever or allergies
• If your medicine causes you blurred vision, drowsiness, poor co-ordination, poor attention

If you are driving less than 2000 miles a year, once you consider insurance, tax, MoT, repairs, maintenance, parking and petrol, you may actually find it is cheaper to get taxis and busses, and walk the short journeys.

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You should not need any regular blood or other tests to check on your SSRI.

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