SSRI antidepressants

Also called selective serotonin re-uptake inhibitors

Selective serotonin re-uptake inhibitors (SSRIs) are used to treat depression and many other conditions such as anxiety, obsessive-compulsive disorder (OCD) and post-traumatic stress disorder (PTSD).

On this page, you can find the following information:

Which SSRIs are available in Aotearoa New Zealand?

What conditions are SSRIs used for?

Although SSRIs are called antidepressants and are commonly used to treat moderate-to-severe depression, they are also used to treat many other conditions such as anxiety disorders (social anxiety, generalised anxiety, panic disorder, OCD and PTSD), eating disorders such as bulimia nervosa, and mood changes related to periods (menstruation) called premenstrual dysphoric disorder. 

We don't know for certain, but researchers think that SSRIs work by increasing the activity of serotonin which is thought to improve mood, emotion and sleep. 

SSRIs are the most frequently prescribed antidepressants. For depression, they are usually the first choice medicine as they have fewer side effects than most other types of antidepressants. Read more about antidepressants.  

It is useful to use SSRIs alongside non-medication treatments such as counselling, exercise and good sleep.

What are the benefits of taking SSRIs?

SSRIs can improve your mood, so that you feel better. You may feel less worried about difficult life events and have fewer negative thoughts. You may find that you have more energy, may sleep better, and may concentrate better. SSRIs are also effective for reducing panic attacks, general worries and anxiety.

Keep taking your SSRI every day. It may take 4 to 6 weeks to notice the full benefits of the medication.

What are the possible side effects?

Like all medicines, SSRIs can cause side effects, but not everyone gets them.

When you first start taking SSRIs, they can cause nausea (feeling sick), vomiting (being sick), having trouble sleeping (insomnia), sweating, anxiety or restlessness and diarrhoea (runny poos).

Worsening of depression and suicidal thoughts can happen in the first few days or weeks of starting an SSRI. It is very important to talk to your healthcare provider if you have these feelings.

See the individual medicine pages for more information on side effects of each SSRI.

Is there any difference between the different SSRIs?

The different SSRIs seem to work just as well in improving the symptoms of depression. SSRIs differ in their risks, type of side effects and interactions with other medicines. This means that the choice of SSRI for you will depend on whether you have other medical conditions, if you are taking other medication, your response to antidepressant medication in the past and the possible side effects.

When can I expect to feel better?

The antidepressant effects of SSRIs are not immediate. It may take 4 to 6 weeks before you notice the full benefits and you should start to feel better after 1 to 2 weeks.

When you first start taking an SSRI, you may notice side effects such anxiety, restlessness and agitation, tiredness or lack of motivation and interest (which can be mistaken for your condition) and sleeping problems. You may feel that your depression symptoms get worse at first because of the initial side effects. Keep in mind that things will get better and these side effects will usually pass as your body gets used to the new medication. Tell your doctor if these effects are ongoing or bother you.

How long will I need to take SSRIs for?

It is recommended that antidepressants are continued for at least 6 months after you feel better. Your doctor may recommend that you take it for longer. Talk to your doctor about how long you should take your SSRI for. 

If I am having a bad day, will an additional dose help?

No, never take more than the dose that’s prescribed. SSRIs do not take effect immediately. The body's response is based on regular levels of medication over several weeks, not hours or minutes.

Can I drink alcohol while taking SSRIs?

Avoid alcohol while you are taking SSRIs, especially when you first start treatment. Drinking alcohol while taking SSRIs can cause drowsiness and affect concentration, putting you at risk of falls and other accidents. It can also cause agitation, aggression and forgetfulness. If you do drink alcohol, drink only small amounts and see how you feel. Do not stop taking your medication.

What if SSRIs do not help?

After starting you on an SSRI, your doctor will monitor your symptoms. If, after at least 6 weeks of being on the SSRI, your symptoms do not improve your doctor may try you on another SSRI or a different type of antidepressant. Do not stop taking your SSRI without speaking to your doctor about your concerns.

What happens if I stop taking SSRIs abruptly?

SSRIs can cause withdrawal symptoms if stopped suddenly. The most common symptoms are dizziness, vertigo, nausea, tiredness, and headache. You may also have similar symptoms to those you had before starting the medication (such as depression, anxiety, irritability). More serious withdrawal symptoms include feelings like electric shocks, and seizures (fits). To avoid this, its best to stop SSRIs gradually, where your dose is reduced slowly over at least 4 weeks.

Learn more

The following links provide further information about SSRIs. Be aware that websites from other countries may have information that differs from New Zealand recommendations.

SSRI antidepressants Patient Info, UK
Antidepressant medicines explained NPS MedicineWise, Australia


  1. Depression or distress? Examining SSRI prescribing in primary care BPAC, NZ, 2019
  2. A primary care approach to sodium and potassium imbalance BPAC, NZ, 2011
  3. Serotonin syndrome – short time to onset, even with the first dose Medsafe Prescriber Update, NZ, 2016
  4. Sexual dysfunction associated with antidepressants and antipsychotics Medsafe Prescriber Update, NZ, 2015
  5. Can I have a drink with that? Medsafe Prescriber Update, NZ, 2014

Useful resources for healthcare professionals

  1. Selective serotonin re-uptake inhibitors NZ Formulary, NZ
  2. Royal Australian and New Zealand College of Psychiatrists clinical practice guidelines for mood disorders Australian and New Zealand Journal of Psychiatry, NZ
Credits: Sandra Ponen, Pharmacist. Reviewed By: Maya Patel, MPharm PGDipClinPharm, Auckland Last reviewed: 16 May 2022