The side effects of antidepressants can cause problems at first but then generally improve with time.
It is important to persist with treatment, even if you are affected by side effects, as it will take several weeks before you begin to benefit from treatment.
With time you should find that the benefits of treatment outweigh any problems related to side effects.
SSRIs and SNRIs
Common side effects of selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) include:
These side effects should improve over time though some can occasionally persist.
TCAs
Common side effects of tricyclic antidepressants (TCAs) include:
- dry mouth
- constipation
- sweating
- problems passing urine
- slight blurring of vision
- drowsiness
The side effects should ease after 7-10 days as your body begins to get used to the medication.
MAOIs
Common side effects of monoamine oxidase inhibitors (MAOIs) include:
- blurred vision
- dizziness
- feeling sick
- shaking or trembling
- difficulty sleeping
In rare cases, MAOIs have the potential to cause a wide range of other side effects. You should check with your GP if you are concerned about any unusual symptoms that you have.
There have been cases where MAOIs have caused a dangerous rise in blood pressure. This can cause symptoms such as:
- a stiff neck
- severe headache
- chest pains
- feeling or being sick
- an abnormally fast heartbeat
If you experience the combination of symptoms listed above, seek emergency medical help immediately by dialling 999 to ask for an ambulance.
SSRIs, SNRIs and serotonin syndrome
Serotonin syndrome is an uncommon, but potentially serious, set of side effects linked to SSRIs and SNRIs.
Serotonin syndrome occurs when the levels of serotonin in your brain become too high. It is usually triggered when you take an SSRI or SNRI in combination with another medication (or substance) that also raises serotonin levels, such as another antidepressant or St John’s Wort.
Symptoms of mild to moderate serotonin syndrome include:
- confusion
- agitation
- muscle twitching
- sweating
- shivering
- diarrhoea
If you experience the symptoms listed above, you should stop taking the medication and seek immediate advice from your GP. If this is not possible, call NHS Direct on 0845 46 47.
Symptoms of severe serotonin syndrome include:
- a very high temperature (fever) of 39.4°C (103°F) or above
- seizures (fits)
- irregular heartbeat (arrhythmia)
- unconsciousness
Hyponatremia
Elderly people who take SSRIs may experience a severe fall in sodium (salt) levels known as hyponatremia. This may lead to a build-up of fluid inside the cells of the body, which can be potentially dangerous.
This side effect can occur as SSRIs can block the effects of a hormone that helps regulate levels of sodium and fluid in the body.
Elderly people are vulnerable because fluid levels become more difficult for the body to regulate.
Mild hyponatremia can cause the following symptoms:
- feeling sick
- headache
- muscle pain
- reduced appetite
- confusion
Moderate to severe hyponatremia can cause the following symptoms:
- feeling listless and tired
- disorientation
- agitation
- psychosis (being unable to tell the difference between reality and your imagination)
- seizures (fits)
The most serious cases of hyponatremia can cause:
If you suspect that you (or someone in your care) have mild hyponatremia you should call your GP for advice and stop the dosage of SSRIs.
If you suspect severe hyponatremia, call 999 and ask for an ambulance.
Hyponatremia can be treated by feeding a sodium solution into the body through an intravenous drip.
Those thought to be at risk may have their sodium levels measured before being given a course of SSRIs and then for a number of weeks afterwards (most cases of SSRI-related hyponatremia occur in the first weeks of treatment).
Sodium levels can be measured by a blood test.
Diabetes
Long-term use of SSRIs and TCAs has been linked to an increased risk of developing type 2 diabetes.
A study published in 2010 found that people who took these types of antidepressants each day for more than a year were twice as likely to develop type 2 diabetes than the population at large.
This increase in risk may be due to weight gain in some people using antidepressants for a long time. If you are overweight you are more likely to develop type 2 diabetes.
Antidepressants and suicide risk
Some people experience suicidal thoughts and a desire to self-harm when they first take antidepressants. Young people under 25 seem particularly at risk.
Contact your GP, or go to hospital immediately, if you have thoughts of killing or harming yourself at any time while you are taking antidepressants.
It may be useful to tell a relative or close friend you have started taking antidepressants and ask them to read the leaflet that comes with your medication. You should then ask them to tell you if they think your symptoms are getting worse, or if they are worried about changes in your behaviour.
