MAOIs – Monoamine oxidase inhibitors

Monoamine oxidase inhibitors (MAOIs) are a group of antidepressants. They can be divided into two types:

  • irreversible MAOIs: which include phenelzine (Nardil) and tranylcypromine (Parnate)
  • reversible MAOI, (also called a reversible inhibitor of monoamine oxidase A [RIMA]): moclobemide. The information below does not apply to moclobemide — see the moclobemide page for more information about this medicine.

Irreversible MAOIs (phenelzine and tranylcypromine), are one of the oldest types of antidepressant. They are not commonly used now because they have potentially serious interactions with many other medicines and foods, and safer antidepressants are available. However, they may be useful for particular kinds of depression that aren’t helped by other treatments.

How do MAOIs work?

Adrenaline, noradrenaline, dopamine and serotonin are neurotransmitters — chemicals that relay signals between the cells in your brain. MAOIs increase the amount of these neurotransmitters in your brain, and this is how they are thought to improve the symptoms of depression.

How effective are MAOIs?

About 50% of people treated with antidepressants find their depression symptoms are halved.

Although all antidepressants have shown similar efficacy when tested in groups of people in clinical trials, keep in mind that individuals can find one antidepressant works better for them than another. So if the first antidepressant you try doesn’t seem to be working for you after a few weeks, talk to your doctor about switching to another. A psychological therapy, such as cognitive behavioural therapy (CBT), could also be an option.

People who should take extra care with MAOIs

Make sure you tell your doctor if you have, or have had in the past, any of the following (you might need to take extra precautions, or another medicine might be more suitable):

  • cardiovascular disease
  • cerebrovascular disease (e.g. stroke or transient ischaemic attack [TIA])
  • angina
  • enlarged prostate
  • epilepsy
  • bipolar disorder
  • liver disease
  • tumours of the adrenal gland.

Get advice about the risks of taking antidepressants, directly from your doctor or from a specialist information line, if you are pregnant, breastfeeding or thinking about becoming pregnant. See Antidepressants, pregnancy and breastfeeding.

Older people are at higher risk of interactions between MAOIs and other medicines, and of cardiovascular side effects (particularly low blood pressure when standing up).

Side effects of MAOIs

Side effects of MAOI antidepressants as a group are listed below. For the side effects of individual medicines, see the consumer medicine information (CMI).

Not everyone experiences these side effects — the way an antidepressant affects you is quite an individual thing, so you might need to try more than one to find the one that suits you best. Some of the side effects will last only a week or two after you first start taking the medicine (e.g. insomnia, nausea, dizziness), while others tend to persist.

Remember that the risk of side effects with any medicine needs to be weighed against its benefit in treating your condition. Your doctor can help you weigh up the risks and benefits of taking particular medicine. See also Is this medicine right for me?

Frequency of side effects with MAOIs

Common (1% of people or more)
Infrequent (between 0.1% and 1% of people)
Rare (fewer than 0.1% of people)

Dizziness on standing

Sleep disturbances (including insomnia and, less commonly, excessive sleeping)

Headache

Drowsiness

Fatigue

Weakness

Agitation

Tremors

Twitching

Involuntary muscle jerks

Exaggerated reflexes

Constipation

Dry mouth

Weight gain

Impotence

Loss of libido

Abnormal changes in liver function tests

Itch

Rash

Sweating

Blurred vision

Fluid retention and swelling

Mania (overexcitement and uninhibited behaviour)

Hypertensive crisis due to food or medication interactions (severe headache and rapid rise in blood pressure which can cause bleeding in the brain or heart failure)

Liver damage

Low white blood cell count

Syndrome of inappropriate antidiuretic hormone secretion (SIADH). This causes your body to retain more water and lowers blood sodium, which can have serious consequences (seizures, coma or death)

Important food interactions with MAOIs

Foods containing tyramine can interact with MAOIs and cause a hypertensive crisis. This causes a dangerous, rapid rise in blood pressure which can result in bleeding in the brain or heart failure.

Foods and drinks to avoid while taking a MAOI, and for 2 weeks after you have stopped taking it, include:

  • matured or out-of-date cheese
  • fermented, matured or aged meat or liver products (e.g. salami, pate)
  • improperly stored or spoiled meat, fish or poultry
  • yeast extracts (e.g. Vegemite, Promite)
  • protein extracts
  • soy sauce and soy bean extracts (e.g. tofu, miso)
  • fava or broad bean pods
  • sauerkraut
  • pickled herring
  • banana peel, banana chips and banana-flavoured desserts
  • beer
  • chianti.

MAOIs and alcohol

MAOIs may make you drowsy and increase the effects of alcohol. If you are affected, do not drive or use machinery. Some kinds of alcohol may also cause a dangerous, rapid rise in blood pressure.

MAOIs and driving operating machinery

MAOIs can make you drowsy — if you are affected, do not drive or use machinery.

For more information

References