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ANTIDEPRESSANTS-SSRIs (Selective Serotonin Reuptake Inhibitors)


This class of medication is useful for the treatment of a number of common and distressing conditions.

ssri s


fluoxetine (Prozac) paroxetine (Aropax) citalopram (Cipramil) fluvoxamine sertraline (Zoloft)

Use: Antidepressants

The SSRI group of medicines are used mainly for depression. They have not been shown to work any better than the old "tricyclic antidepressants" such as amitriptyline, but have been shown to be more acceptable to many people, with less severe or less frequent side effects. They take time to work - it usually takes two weeks for their beneficial effects to begin and up to six weeks to gain best effect. There are some differences between these antidepressants, so people may find one works better or has less side effects for them than another.

For treatment of:

Depression, Obsessive Compulsive Disorder, Panic Disorder, Social Anxiety Disorder/Social Phobia, Bulimia Nervosa, Premenstrual Dysphoric Disorder (a severe form of PMS).

How they work

Nerve cells in the brain communicate by chemicals (neurotransmitters). Some of these including serotonin are important in determining mood and behaviour.

This group of antidepressants stop reuptake of serotonin (allowing levels between cells to increase)and this is how they are thought to work on depression and other disorders listed above. Some of the medicines listed above may not be approved for use in all of the different uses given. The recommended dose of the medicine depends on the use, e.g. fluoxetine has a recommended initial dose of 20mg/day for depression, up to 60 mg/day for bulimia nervosa and 20mg/day for premenstrual dysphoric disorder.

Risk Factors:

Do not take if you have had an allergy with the same medicine before. It is important not to take any of this group of medicines if taking mono amine oxidase inhibitors (e.g. tranylcypromine, Parnate). This includes the newer reversible MAOIs (e.g. moclobemide, Aurorix).

If any of the following factors are present the doctor may not want to use the SSRI antidepressants, or may want to keep special watch:

  • Using neuroleptics (e.g. chlorpromazine)
  • A history of mania (a phase of hyperexcitability. hyperactivity, agitation and elation)
  • Some heart conditions
  • Diabetes & hypoglycaemia (low blood sugar) may possibly occur during treatment, and hyperglycaemia (high blood sugar) after stopping treatment with SSRI antidepressants
  • Pregnancy or breastfeeding
  • Narrow-angle glaucoma
  • Using diuretics.


Side effects:

These medicines are generally well tolerated and not many people want to stop taking them because of side effects. The side effects can start before you see a benefit, and some can disappear as your body gets used to the medicine. The more common side effects are:

  • Diarrhoea
  • Nausea
  • Dizziness
  • Sleepiness
  • Insomnia (difficulty sleeping)
  • Dry mouth
  • Muscle weakness or tremor
  • Anxiety/nervousness (which may pass as the tablets begin to help the depression)
  • Reduced appetite.

These side effects are mainly mild, however if you are dizzy or drowsy you must not drive a car or operate machinery. These medicines are usually taken in the morning because they can keep you awake at night.


There are a number of interactions with other medicines, so always check with your pharmacist or doctor when taking a SSRI antidepressant and using other medicines. An interaction does not necessarily mean you can not use two medicines together, but can mean dosage of one or the other may need to be altered. For instance, Fluoxetine (Prozac) stays in the body for some time after you stop taking it, so if you need to use another medicine within 5 weeks after stopping fluoxetine, check with your doctor or pharmacist in case there will be any problem.

Do not use with: MAOI medicines e.g. tranylcypromine (Parnate). Tryptophan.

Take care with:

  • Neuroleptics e.g. chlorpromazine, clozapine
  • Diuretics
  • Anticonvulsants - carbamazepine, phenytoin, sodium valproate
  • Warfarin
  • Cimetidine
  • Procyclidine
  • Tricyclic antidepressants
  • Some anti-arrhythmic medicines. 

This list does not include all possible interactions, and some SSRI medicines may not interact with all the medicines above.

Patient information:

Follow the instructions on the label of the medicine or as directed by your doctor. Talk to a doctor immediately if you get a rash. These medicines will take around 2 weeks to begin working and 6 weeks to gain best effects - you may need to be patient. If you do not think the medicine is helping, talk to your doctor. Do not share your medicine with anyone else, or "borrow" medicine off anyone. This medicine should be taken every day as directed and it will not work if you only take it now and then. Always talk to your doctor and pharmacist if you get other medicines to make sure that they are compatible.

These medicines are not addictive.

Talk to your doctor if you are planning to stop taking these medicines as you may need to gradually taper your dose before stopping. If you have dizziness or drowsiness or other symptoms that may affect your coordination or reaction time, avoid driving a car or operating machinery. If you are planning to get pregnant, talk to your doctor first about continuing this medicine.

Duration of treatment;

Usually , episodes of depression need to be treated for at least 6 months to reduce the risk of relapse. In certain circumstances and for other conditions , longer periods of treatment are needed. It is best to discuss the timing and advisability of changing or stopping medication with your doctor

This information is intended to give a general overview. It relates to SSRI medicines as a group, and not to any one individual medicine. Interactions, cautions for use, uses and side effects may vary for individual medicines, from the information given above. Your doctor or pharmacist will have access to more information about individual medicines.

See also:

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