Antidepressants

Published by Bupa's Health Information Team, April 2011.

This factsheet is for anyone taking antidepressants, or who would like information about them.

Antidepressants are used in the treatment of depression and a number of other conditions. This factsheet provides information on some of the most common types of antidepressant.

Why would I take antidepressants?

Your doctor may prescribe antidepressants if you have depression. This is a condition in which you may have a low mood, a loss of interest in everyday activities, feelings of low self-worth, a lack of energy and poor concentration. The symptoms may last for a long time.

Depression may be classed as mild, moderate or severe. This depends on your symptoms and how much they interfere with your everyday life. Antidepressants aren’t usually needed for mild depression. Psychological therapies, or talking treatments, such as counselling or cognitive behavioural therapy (CBT) may be better for this type of depression. Antidepressants are usually prescribed for moderate or severe depression. However, you should also have psychological therapy alongside taking antidepressants.

Antidepressants can also be used in the treatment of other conditions, such as chronic (long-lasting) pain, anxiety and panic attacks, and obsessive compulsive disorder.

What are the main types of antidepressant?

There are a number of different classes of antidepressant. These include: selective serotonin reuptake inhibitors (SSRIs), tricyclics, monoamine-oxidase inhibitors (MAOIs), serotonin and noradrenaline re-uptake inhibitors (SNRIs) and noradrenaline and specific serotoninergic antidepressants (NaSSAs). There is also a newer medicine licensed for the treatment of depression, called agomelatine. All of these work well for moderate and severe depression but have different side-effects.

Your doctor will assess your symptoms and the potential side-effects and prescribe the most suitable medicine for you. Most people are prescribed an SSRI to start with. However, your doctor may prescribe other types of antidepressant if SSRIs haven’t worked or aren’t suitable for you.

How do antidepressants work?

It's not fully understood what happens in your brain when you have depression. However, it's known that people with depression usually have reduced levels of certain brain chemicals called neurotransmitters, particularly two called noradrenaline and serotonin.

Neurotransmitters are released by nerve cells. They carry information across the tiny gap between one nerve cell and the next. Once they have done their job, neurotransmitters are re-absorbed into the nerve cell – this is called re-uptake.

Antidepressants work as treatments for depression because they increase levels of serotonin and/or noradrenaline. The SNRIs, NaSSAs, tricyclics and MAOIs increase levels of both noradrenaline and serotonin, while SSRIs increase levels of serotonin only. These medicines work by either encouraging your nerve cells to make more of the neurotransmitters or by preventing their re-uptake.

Agomelatine works on another chemical in your body called melatonin, as well as serotonin.

How to take antidepressants

Antidepressants are only available with a prescription from your doctor - this may be from your GP or if you have been referred to a psychiatrist (a doctor who specialises identifying and treating mental health conditions), he or she may prescribe them. Antidepressants come as tablets or capsules and sometimes in a liquid form. It’s important to take your medicine as prescribed by your doctor.

It usually takes around two to four weeks before antidepressants start to have an effect. You will need to visit your doctor regularly when you first start taking antidepressants to see how well they are working. If they aren’t working well after four to six weeks, your doctor may consider increasing the dose or prescribing you a different antidepressant to see if it works better for you.

If you find an antidepressant that works for you, you will probably need to carry on taking it for at least six months, even once your symptoms have gone away. This can help prevent depression coming back. You may need to take antidepressants for two years or more if you get repeated bouts of depression.

Always ask your doctor for advice and read the patient information leaflet that comes with your medicine.

Special care

If you have heart problems, or if you're pregnant or breastfeeding, tell your doctor before taking an antidepressant. Certain antidepressants are safer for people who have heart problems, or for women who are pregnant or breastfeeding.

Side-effects of antidepressants

All antidepressants have some side-effects. Taking certain antidepressants can slow down your reaction speeds and affect activities that require concentration, such as driving. Ask your doctor whether it’s safe for you to drive while taking your medicine. All antidepressants can affect your sex life – talk to your GP if you’re worried about this.

Antidepressants aren't addictive but you may get withdrawal symptoms if you stop taking them suddenly. Symptoms of sudden withdrawal include feeling sick, vomiting, loss of appetite, headaches, dizziness, chills, sweating and sometimes anxiety and panic. If you want to stop taking antidepressants, talk to your doctor first. He or she may suggest that you reduce the dose slowly, over a period of weeks, as this can help to prevent withdrawal symptoms.

Always read the patient information leaflet that comes with your medicine and if you're worried about possible side-effects, ask your doctor for advice. Below we describe common side-effects for some of the main classes of antidepressants.

Selective serotonin re-uptake inhibitors

Although SSRIs have some side-effects, they are generally less troublesome than those of other antidepressants and hence are prescribed most often. In particular, they are less likely to make you feel drowsy. Common side-effects of SSRIs include:

• feeling sick or vomiting
• indigestion
• diarrhoea or constipation

Less commonly, SSRIs can cause:

• weight loss
• anxiety
• headaches
• skin reactions, such as a rash
• insomnia
• shaking
• dizziness
• dry mouth
• fits

Side-effects of SNRIs and NaSSAs tend to be similar to those of SSRIs.

Tricyclic antidepressants

Common side-effects of tricyclics include:

• drowsiness or tiredness
• dizziness
• anxiety
• confusion
• irritability
• dry mouth
• blurred vision
• constipation
• difficulty passing urine

Some of these side-effects settle down with time, so you should carry on taking your medicine if you get these symptoms. Don’t stop taking your antidepressants without speaking to your doctor first.

Rarely, tricyclics may also cause arrhythmias (heart palpitations) and fits. Because of this, they are used less often than SSRIs.

Monoamine-oxidase inhibitors

MAOI antidepressants can interact with other medicines and some common foods, increasing the risk of side-effects. Because of this, MAOIs aren't prescribed very often. If you’re taking a MAOI antidepressant, your doctor will give you a list of foods that you shouldn’t eat.

Side-effects of MAOIs can include:

• headaches
• insomnia
• constipation
• dizziness

Interactions of antidepressants with other medicines

Herbal remedies contain active ingredients and may interact with other medicines or cause side-effects. Don’t start taking any herbal remedies without speaking to your doctor or pharmacist first. St John's wort, which is sold as a herbal antidepressant, can be harmful when taken with prescribed antidepressants.

Names of common antidepressants

Examples of the main types of antidepressants are shown in the table below.

Each medicine has a generic name, which is its official medical name. Many medicines also have at least one brand name, which is the trade name. Generic names are written in lower case and brand names start with a capital letter.

If you're not sure which medicine you have been prescribed, ask your pharmacist for advice.

For answers to frequently asked questions on this topic, see FAQs.

For sources and links to further information, see Resources.

Other antidepressants

Alternatives to tricyclics and SSRIs include venlafaxine (Efexor), reboxetine (Edronax) and mirtazapine (Zispin). These also work by affecting the levels of neurotransmitters in your brain and may work better for specific symptoms. They may also be an option if a tricyclic or SSRI hasn't worked for you.

Another group of antidepressants known as monoamine oxidase inhibitors (MAOIs) is also available. Medicines in this group include phenelzine (Nardil) and moclobemide (Manerix). MAOIs can have lots of interactions with other medicines and foods such as cheese, increasing the risk of side-effects. They aren't commonly prescribed, but may be worth trying if other types of antidepressant haven't worked for you.

For answers to frequently asked questions on this topic, see FAQs.

For sources and links to further information, see Resources.