Like all medicines, antidepressants can cause side effects in some people. But these generally improve with time.
It can take a few weeks to feel the benefits of the antidepressants. But the benefits usually outweigh any problems you have with side effects.
At the start, you'll usually see your GP or a specialist nurse at least once every 2 to 4 weeks. They will monitor side effects and check how well the medicine is working.
For information about your medicine and side effects, read the patient leaflet that came with it.
Non-urgent advice: Find your patient information leaflet
Your patient information leaflet is the leaflet that comes with your medicine. You can find a digital version of the leaflet online.
Report side effects
You can report any suspected side effects to the Health Products Regulatory Authority (HPRA): report an issue - hpra.ie
Common side effects of antidepressants
Common side effects usually ease after a couple of weeks as your body gets used to the medicine. But some may continue.
The side effects you experience may depend on the type of antidepressant you're taking.
SSRIs and SNRIs
Selective serotonin reuptake inhibitors (SSRIs) and serotonin-noradrenaline reuptake inhibitors (SNRIs) are the most common types of antidepressants.
Side effects of SSRIs and SNRIs can include:
- feeling agitated, shaky or anxious
- feeling sick (nausea)
- getting sick (vomiting)
- indigestion and stomach aches
- diarrhoea or constipation
- loss of appetite
- dizziness
- not sleeping well (insomnia), or feeling very sleepy
- headaches
- low sex drive
- difficulties achieving orgasm
- in men, difficulties getting or keeping an erection (erectile dysfunction)
Tricyclic antidepressants (TCAs)
Common side effects of TCAs include:
- dry mouth
- slight blurring of vision
- constipation
- difficulty peeing
- drowsiness
- dizziness
- weight gain
- excessive sweating - especially at night
- heart rhythm problems, such as noticeable palpitations or a fast heartbeat (tachycardia)
Important
Some antidepressants can cause:
- dizziness
- drowsiness
- blurred vision
Stop driving, cycling or operating tools or machinery for the first few days. You will know then how the medicine makes you feel.
Potential health risks from antidepressants
There are some potential health risks linked to antidepressants.
If you are concerned about side effects, talk to your GP or specialist.
Serotonin syndrome
Serotonin syndrome is a serious set of side effects that you can get with SSRIs and SNRIs. Serotonin syndrome is not common.
It happens when the levels of a chemical in your brain called serotonin become too high. It can happen if you take an SSRI or SNRI with another medicine or remedy that raises serotonin levels. For example, another antidepressant or a herbal remedy such as St John’s wort.
Symptoms of serotonin syndrome can include:
- confusion
- agitation
- muscle twitching
- sweating
- shivering
- diarrhoea
Urgent advice: Contact your GP or GP out of hours urgently if:
Emergency action required: Call 112 or 999 and ask for an ambulance if
you or someone else has symptoms of severe serotonin syndrome including:
- a very high temperature (fever)
- seizures (fits)
- irregular heartbeat (arrhythmia)
- unconsciousness
You need emergency medical help.
Hyponatraemia
If you take antidepressants and are age 75 or older, your level of sodium (salt) in your blood can fall. This is called hyponatraemia.
This can lead to a build-up of fluid in your body, which can be dangerous.
The antidepressant can block the hormone that regulates the levels of sodium and fluid in your body. It is also harder for your body to regulate your fluid levels as you get older.
Symptoms of mild hyponatraemia include:
- feeling sick (nausea)
- headache
- muscle pain
- reduced appetite
- confusion
Urgent advice: Contact your GP urgently if:
- you suspect mild hyponatraemia
Stop taking SSRIs.
Symptoms of more severe hyponatraemia include:
- listlessness and tiredness
- disorientation
- agitation
- psychosis
- seizures (fits)
If hyponatraemia is very severe, it can stop you breathing or cause a coma.
Emergency action required: Call 112 or 999 and ask for an ambulance if:
- you suspect severe hyponatraemia
Your doctors usually treat hyponatraemia by injecting sodium into your blood through a drip (intravenously).
Diabetes
Long-term use of SSRIs and TCAs has been linked to an increased risk of developing type 2 diabetes. But it's not clear if they cause diabetes directly.
Some people gain weight when using antidepressants. This can increase your risk of developing type 2 diabetes.
Your doctor may give you advice about:
- keeping active
- healthy eating
- social activities to boost your mood
Suicidal thoughts
In very rare cases, people have thoughts about self-harm or ending their lives when they start taking antidepressants. People age 25 or younger seem more at risk.
Treating depression with medicine and talking treatments greatly reduces the risk of suicide.
Emergency action required: Contact your GP, or go to emergency department immediately if:
- you have thoughts about harming yourself
It may be useful to tell a family member or close friend if you've started taking antidepressants.
Ask them to read the leaflet that comes with your medicine. Then ask them to tell you if they think your symptoms get worse. Or if they're worried about changes in your behaviour.