There are several important things to consider when taking antidepressants. You should discuss these with your GP or mental health professional.

Interactions with other medications

Antidepressants can react unpredictably with other medications, including over-the-counter medications such as ibuprofen. Always carefully read the patient information leaflet that comes with your medication to see if there are any medications you should avoid.

If in doubt, your pharmacist or GP should be able to advise you.

Pregnancy

As a precaution, antidepressants are not usually recommended for most pregnant women, especially during the early stages of a pregnancy. However, exceptions can be made if the risks posed by depression (or other mental health conditions) outweigh any potential risks of treatment.

Potential complications that have been linked to antidepressant use during pregnancy include:

• loss of the pregnancy
• birth defects affecting the baby’s heart (congenital heart disease)
• a rare condition in newborns called pulmonary hypertension, where the blood pressure inside the lungs is abnormally high, causing breathing difficulties

However, there is no hard evidence that antidepressants cause these complications.

If you are pregnant and depressed you should discuss the pros and cons of treatment with antidepressants with the doctor in charge of your care.

If antidepressants are recommended they will usually be a type called a selective serotonin reuptake inhibitor (SSRI), such as fluoxetine.

Breastfeeding

As a precaution, the use of antidepressants if you are breastfeeding is not usually recommended.

But there are circumstances when both the benefits of treatment for depression (or other mental health conditions) and the benefits of breastfeeding your baby outweigh the potential risks.

If you are treated with antidepressants when breastfeeding, then paroxetine or sertraline is normally recommended.

Children and young people

The use of antidepressants is not usually recommended in children and young people under the age of 18. This is because there is evidence that they can trigger thoughts about suicide and acts of self-harm in this age group.

Concerns have also been raised that their use could affect the development of the brain in children and young people.

An exception can usually only be made if the following points are met:

• the person being treated has failed to respond to talking therapies such as cognitive behavioural therapy, and
• the person being treated will continue to receive talking therapies in combination with antidepressants, and
• the treatment is supervised by a psychiatrist (a doctor who specialises in treating mental health conditions)

If an antidepressant is recommended, then fluoxetine is usually the first choice.

Alcohol

You should be wary of drinking alcohol if you are taking antidepressants as alcohol is itself an depressant and drinking alcohol can make your symptoms worse.

If you drink alcohol while taking types of antidepressants called tricyclic antidepressants (TCAs) or monoamine oxidase inhibitors (MAOIs), you may become drowsy and dizzy. Many alcoholic drinks also contain the protein tyramine (see below), which can cause a dangerous rise in blood pressure if you are taking an MAOI.

You are less likely to experience unpleasant or unpredictable effects if you drink alcohol while taking a selective serotonin reuptake inhibitor (SSRI) or a serotonin-noradrenaline reuptake inhibitor (SNRI) antidepressant, but avoiding alcohol is often still recommended in these cases.

Illegal drugs

The use of illegal drugs is not recommended if you are taking antidepressants, particularly if you have been prescribed an MAOI or a TCA. This is because they can cause unpredictable and unpleasant effects.

In particular, you should avoid taking:

• cannabis – smoking cannabis while taking a TCA can make you feel very ill
• amphetamines (speed)
• cocaine
• heroin
• ketamine

As with alcohol, illegal drugs can make symptoms of depression or other mental health conditions worse.

Other antidepressants

You should never take two different types of antidepressants, such as a TCA and an MAOI, unless advised by the doctor in charge of your care. This is because taking certain combinations of antidepressants can make you feel very ill and can be life-threatening.

If a decision is taken to switch you from one type to another, the dosage of the first antidepressant will usually be gradually reduced before the second is administered.

St John’s Wort

St John’s Wort is a popular herbal remedy promoted for the treatment of depression.

While there is evidence of its effectiveness many experts advise against its use because the amount of active ingredient varies among individual brands and batches, making the effects unpredictable.

Taking St John's Wort with other medications, such as anticonvulsants, anticoagulants, antidepressants and the contraceptive pill, can also cause serious health problems.

You shouldn't take St John's Wort if you are pregnant or breastfeeding, as it is unclear whether it is safe.

Driving and operating machinery

Some antidepressants can cause dizziness, drowsiness and blurred vision, particularly when you first start taking them.

If you do experience these problems, you should avoid driving or using tools and machinery.

Cautions for specific antidepressants

SSRIs

Selective serotonin reuptake inhibitors (SSRIs) may not be suitable for you if you have:

• bipolar disorder  (alternating bouts of depression and mania) and you are in a manic phase (a period of extremely excitable mood), although they can be useful for depressive phases
• a bleeding disorder, or if you are taking medicines that make it more likely that you may bleed (for example, warfarin)
• type 1 diabetes and type 2 diabetes
• epilepsy – SSRIs should only be taken if your epilepsy is well controlled, and the medication should be stopped if your epilepsy gets worse
• kidney disease

SNRIs

Serotonin-noradrenaline reuptake inhibitors (SNRIs) may not be suitable for you if you have a history of heart disease or you have poorly controlled high blood pressure.

TCAs

Tricyclic antidepressants (TCAs) may not be suitable for you if you have:

• a history of heart disease
• recently had a heart attack
• liver disease
• an inherited blood disorder called porphyria
• bipolar disorder
• schizophrenia
• a growth on your adrenal glands that is causing high blood pressure (pheochromocytoma)
• an enlarged prostate gland 
• narrow angle glaucoma – increased pressure in the eye
• epilepsy

MAOIs

Although they are not commonly prescribed nowadays, monoamine oxidase inhibitors (MAOI) may not be suitable for you if you have:

• a history of heart disease
• liver disease
• bipolar disorder
• an overactive thyroid gland
• had a stroke, or another condition that affects the blood supply to the brain

Another important consideration when taking MAOIs is the need to avoid any food or drink containing a type of protein called tyramine. This is because an MAOI can disrupt the body’s ability to break down tyramine and high levels of tyramine can cause a sudden and dangerous rise in blood pressure.

Examples of food containing tyramine include cheese, yeast extract (such as Marmite) and some salted or pickled meats. Ask for a detailed list of foods and drinks to avoid when you are first prescribed your medication.

MAOIs can also react unpredictably to some anaesthetics and sedatives, so you may be advised to stop taking your medication two weeks before having surgery or major dental treatment that requires sedation.