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Monoamine oxidase inhibitor (MAOI) antidepressants

Monoamine oxidase inhibitor (MAOI) antidepressants are used to treat depression. MAOI antidepressants are used when depression has not responded to other medication.

Examples of MAOIs include tranylcypromine (Parnate) and phenelzine (Nardil).

Talking therapies are often used alongside antidepressant medication.

Health professionals believe that antidepressants work by increasing the activity of neurotransmitters. Neurotransmitters are chemicals in our brains. Certain neurotransmitters, such as serotonin and noradrenaline, affect mood and emotion.

How soon MAOI antidepressants work

You may start on a low dose of an MAOI then slowly increase over several weeks to a target dose. This is to reduce the chance of side effects.

It can take between 4 and 6 weeks on your target dose before you get the full effect.

MAOI antidepressant safety

It is usually safe to take MAOI antidepressants as prescribed by your doctor. But they do not suit everyone. Let your doctor know if you have the following, as extra care may be needed:

Discuss any other medicines you take with your pharmacist or healthcare provider. This should include any you buy yourself. Especially cold remedies and hay fever medicines. It should also include nutritional or herbal supplements. And complementary medicines such as St John's wort. This is because other medicines may cause problems with your antidepressants.

Always let your general practice team know that you are taking an MAOI.

Side effects from MAOI antidepressants


Foods and drinks that contain tyramine can interact with MAOI antidepressants. This can cause your blood pressure to rise suddenly. You may experience a severe headache, chest pain and increasing shortness of breath. If you have this reaction, you will need to go to the emergency department at the hospital. See MAOIs and a low tyramine diet for details about food and drinks that can cause this reaction.

Rarely, antidepressants can make you more anxious and restless in the first 2 weeks of taking them. You can even have feelings of self-harm or suicidal thoughts. If this happens, talk to your healthcare provider. Or contact a mental health crisis support line.

If you have minor side effects, try staying on the medicine for a few weeks. Minor side effects often go away after your body gets used to the new medicine.

If the side effects do not go away or if they are worrying you, tell your healthcare provider or pharmacist. They may have suggestions for how to reduce or manage your side effect.

Common side effects of MAOIs include feeling faint when you stand up (postural hypotension) and feeling anxious or agitated. They also include constipation, dry mouth, sleep problems and less interest in or trouble having sex.

Stopping antidepressants

There is no set time for how long you should take antidepressants. Most people will need to take them for at least 6 to 12 months. This can help stop your symptoms coming back.

Antidepressants are not addictive. But if you stop taking them suddenly, you may get some symptoms. This is known as antidepressant withdrawal or discontinuation syndrome.

You need to decrease most antidepressants slowly. You may need to drop the dose by small amounts each week, or every two weeks or every month.

You should talk to your healthcare provider before stopping your medication. They will help you make a plan for how you are going to do this.

For more information, see Stopping antidepressants.

On the next page: MAOIs and a low tyramine diet

Written by HealthInfo clinical advisers. Page created December 2023.


Page reference: 1294358

Review key: HIMMH-215644