MAO Inhibitors: The Antidepressants With a Food List
These were the first modern antidepressants, and they are still among the most effective ever developed. They are also the ones almost nobody is prescribed, because taking them means learning a list of foods and a longer list of medicines that can cause a dangerous rise in blood pressure.
That trade-off explains everything about their position today: rarely started, hard to stop dismissing, and still the answer for a group of people whom nothing else has helped.
⚙️ What the enzyme does. Monoamine oxidase breaks down the signalling chemicals involved in mood — serotonin, noradrenaline and dopamine — and also breaks down substances absorbed from food. Blocking it raises the levels of all of them.
There are two forms. Type A handles serotonin and noradrenaline, and it is the one that matters for depression. Type B handles dopamine, and blocking it is useful in Parkinson disease.
Type A also sits in the gut wall, where its job is to destroy a substance in food called tyramine before it reaches the bloodstream. Block it there and that protection disappears — which is the entire basis of the dietary restriction.
🧀 The reaction the diet prevents
Tyramine forms when protein-containing food ages, ferments or is cured. Normally it is destroyed in the gut and never reaches the circulation. On a non-selective irreversible inhibitor, it passes through intact, displaces stored noradrenaline, and can push blood pressure up sharply within minutes to hours.
🔴 Signs of a hypertensive reaction, which is a medical emergency:
- Sudden severe throbbing headache, usually at the back of the head — the classic first sign
- Palpitations or a pounding heart
- Neck stiffness or soreness
- Nausea and vomiting
- Sweating, sometimes with cold clammy skin
- Chest pain, breathlessness, or visual disturbance
Call emergency services and say clearly which medicine is being taken. Do not wait for it to pass, and do not treat it as an ordinary headache.
🍴 What the food list actually contains
The restriction has narrowed considerably over the decades, because tyramine content depends on ageing and fermentation rather than on food category. Modern advice is far less sweeping than the older versions still circulating.
| Avoid | Generally fine |
|---|---|
| Aged and mature cheeses — cheddar, blue, parmesan, brie, camembert | Fresh cheeses — cottage cheese, ricotta, cream cheese, processed slices |
| Cured, dried and fermented meats — salami, pepperoni, chorizo, dried sausage | Fresh meat, poultry and fish, properly stored |
| Yeast extracts and concentrated meat extracts | Baked goods containing baker yeast |
| Soy sauce, miso, fermented bean pastes | Most other condiments |
| Sauerkraut and other fermented vegetables | Fresh and cooked vegetables |
| Tap beer and unpasteurised beer | Bottled or canned beer and wine in modest amounts |
| Broad bean pods | Most other beans and pulses |
| Anything overripe, left out, or of uncertain age | Freshly prepared food |
The organising principle is freshness. Tyramine accumulates as food ages, so the same item can be safe today and unsafe next week. Leftovers kept several days, food left unrefrigerated, and restaurant dishes of unknown provenance are the practical risks rather than any single ingredient.
Restrictions continue for about two weeks after stopping an irreversible inhibitor, because the body has to manufacture new enzyme rather than simply clear the drug.
💊 The interactions, which matter more than the diet
Food gets the attention. Medicines cause more of the serious incidents, and several of the culprits are bought without a prescription.
🔴 Must not be combined:
- Other antidepressants — SSRIs, SNRIs, tricyclics and others. The risk is serotonin syndrome, which can be fatal
- Tramadol and pethidine, and some other opioid painkillers
- Migraine triptans
- Dextromethorphan, the cough suppressant in a great many cold remedies
- Decongestants — pseudoephedrine and phenylephrine, in cold and flu products and some nasal sprays
- Stimulants, including those used for ADHD
- Buspirone
- Linezolid, an antibiotic that is itself a weak inhibitor
- St John of Jerusalem wort
Two practical consequences. Never buy an over-the-counter cold remedy without asking the pharmacist first — the combination of a cough suppressant and a decongestant in one bottle is exactly the wrong product. And tell dentists, surgeons and anaesthetists, since local anaesthetics containing adrenaline and several anaesthetic drugs need adjusting.
⏳ The washout
Switching to or from one of these drugs requires a gap, and the gap is not negotiable.
- Fourteen days after stopping the inhibitor before starting most other antidepressants
- Fourteen days after stopping most other antidepressants before starting the inhibitor
- Five weeks after stopping fluoxetine, because it and its active breakdown product linger far longer than the rest of the class
Those intervals exist because overlapping the two produces serotonin syndrome. Anyone changing treatment should have the dates written down rather than held in memory, and should know that the gap is uncomfortable and temporary rather than a sign that something has gone wrong.
🧩 The types, and why the restrictions differ
| Type | What it means in practice |
|---|---|
| Non-selective and irreversible | Blocks both forms permanently until new enzyme is made. Full dietary restriction and full interaction list. This is the classic antidepressant group |
| Reversible, type A selective | Detaches from the enzyme, so tyramine can displace it. Far fewer dietary restrictions, and drug interactions still apply |
| Type B selective, low dose | Used in Parkinson disease. At standard doses it does not block the gut enzyme, so no dietary restriction is needed |
| Type B selective, higher dose or skin patch | Selectivity is lost as the dose rises, and dietary restrictions return |
That third row is the source of most confusion. Selegiline, taken for Parkinson disease at usual doses, is a type B inhibitor and does not require the cheese list — a point worth being clear about, since people prescribed it frequently find alarming general warnings about MAO inhibitors and assume they apply. The article on selegiline covers its own considerations, which are different.
What does still apply at Parkinson doses is the interaction list, particularly with antidepressants, tramadol and dextromethorphan. Diet relaxed, medicines still checked.
⭐ Why they have not disappeared
Given all of the above, the obvious question is why anyone still prescribes them. The answer is that for certain people they work when nothing else has.
They have particular value in atypical depression — a pattern with sleeping and eating more rather than less, heavy leaden limbs, mood that lifts briefly with good news, and marked sensitivity to rejection. In that presentation they have historically outperformed other classes.
They also retain a place in depression that has not responded to several other treatments, and in severe social anxiety. Someone who has worked through multiple antidepressants without benefit is exactly the person for whom this class is worth the inconvenience, and their reputation for difficulty means they are frequently never offered.
Beyond the diet and interactions, common effects include low blood pressure on standing with dizziness and falls, insomnia, weight gain, sexual difficulties and, with some, swelling of the ankles.
📋 Living with one safely
- Carry a card stating what you take, for emergencies and for any unplanned medical care
- Ask a pharmacist before every new medicine, including anything bought over the counter
- Treat cold and flu remedies as prohibited by default until checked
- Eat fresh rather than memorising an ever-changing list — freshness is the principle the list is built on
- Avoid restaurant dishes of unknown age, particularly aged cheese, cured meat and soy-based sauces
- Know the headache. A sudden severe throbbing headache is the signal to seek emergency care, not to lie down
- Rise slowly, since dizziness on standing is common
- Keep the washout dates in writing when switching treatments
🩺 When to seek help
- Sudden severe throbbing headache, especially with palpitations or neck stiffness — emergency, and name the medicine
- Chest pain, breathlessness or visual disturbance — emergency
- Agitation, tremor, sweating, fever and muscle twitching after any new medicine — emergency, possible serotonin syndrome
- Before any dental work, surgery or anaesthetic
- Before taking any cold, flu or cough remedy
- Dizziness or falls on standing — the dose may need adjusting
- Before switching antidepressants in either direction — the washout period is mandatory
- New or worsening thoughts of self-harm — same day
This pharmacy does not stock the antidepressant inhibitors of this class. The only related medicine available is Eldepryl (selegiline), a type B selective inhibitor used in Parkinson disease, which at usual doses does not require the dietary restrictions described here but does share the medicine interactions. First-line antidepressant options are stocked in the antidepressants category, including Lexapro (escitalopram) and Cymbalta (duloxetine) — none of which may be combined with a medicine of this class without the washout period above.
❓ Frequently asked questions
Why is there a food list?
Because the same enzyme these drugs block in the brain also sits in the gut wall, where its job is to destroy a substance called tyramine before it enters the bloodstream. With that protection removed, tyramine from aged or fermented food passes through intact and can push blood pressure up sharply within minutes to hours.
What does a dangerous reaction feel like?
It usually starts with a sudden severe throbbing headache, typically at the back of the head, often with palpitations, neck stiffness, nausea and sweating. Chest pain, breathlessness or visual disturbance may follow. It is a medical emergency — call emergency services and say which medicine is being taken rather than waiting for it to pass.
Which foods actually matter?
Aged and mature cheeses, cured and fermented meats, yeast and meat extracts, soy sauce and miso, sauerkraut, tap or unpasteurised beer, and broad bean pods. Fresh cheese, fresh meat and fish, ordinary bread, and bottled beer or wine in modest amounts are generally fine. The organising principle is freshness — tyramine builds up as food ages, so leftovers and food of unknown age are the real risk.
Are the medicine interactions worse than the diet?
In practice yes. Other antidepressants, tramadol and pethidine, migraine triptans, stimulants, buspirone, the antibiotic linezolid and St John of Jerusalem wort are all prohibited. So are two ingredients found in ordinary cold remedies — the cough suppressant dextromethorphan and decongestants such as pseudoephedrine. Never buy an over-the-counter cold product without asking the pharmacist first.
How long is the washout when switching?
Fourteen days in either direction between this class and most other antidepressants, and five weeks after stopping fluoxetine, because it and its active breakdown product persist far longer. The gap exists to prevent serotonin syndrome and is not negotiable. Write the dates down rather than relying on memory.
Do the restrictions apply to selegiline for Parkinson disease?
Not the dietary ones, at usual Parkinson doses. Selegiline is selective for the type B enzyme, which does not guard the gut against tyramine, so the cheese list does not apply. Selectivity is lost at higher doses or with skin patches, where restrictions return. The medicine interactions do still apply, particularly with antidepressants, tramadol and dextromethorphan.
How long do the restrictions last after stopping?
About two weeks for the irreversible inhibitors. The drug itself clears quickly, but the enzyme it disabled has to be manufactured again, and until that happens the protection against tyramine is still missing. Diet and interaction precautions therefore continue for a fortnight after the last dose.
If they are so awkward, why are they still used?
Because for some people they work when nothing else has. They have particular value in atypical depression — sleeping and eating more rather than less, heavy limbs, mood lifting briefly with good news, marked sensitivity to rejection — and in depression that has resisted several other treatments. Their reputation for difficulty means they are often never offered to exactly the people who would benefit.
What other side effects do they cause?
Low blood pressure on standing, with dizziness and a risk of falls, is among the most troublesome and improves with rising slowly. Also insomnia, weight gain, sexual difficulties and ankle swelling with some of them. These are separate from the tyramine reaction and are dose-related rather than food-related.
What should I tell a dentist or surgeon?
That you take a monoamine oxidase inhibitor, before any procedure. Local anaesthetics containing adrenaline, several anaesthetic agents and a number of painkillers used around surgery all need adjusting. Carrying a card stating the medicine covers this and also matters in an emergency where you may not be able to explain it yourself.
📑 Sources and editorial
- Pharmacology of monoamine oxidase subtypes A and B, and of reversible versus irreversible inhibition
- Literature on tyramine pressor response and the mechanism of hypertensive reaction
- Contemporary dietary guidance for monoamine oxidase inhibitor therapy and revision of historical restrictions
- Interaction data covering serotonergic antidepressants, opioids, triptans, dextromethorphan, sympathomimetics and linezolid
- Guidance on washout intervals when switching antidepressants, including extended washout after fluoxetine
- Evidence on selectivity loss with higher-dose and transdermal selegiline
- Comparative trial evidence in atypical depression and treatment-resistant depression
- Perioperative guidance for patients on monoamine oxidase inhibitors
- Related reading: selegiline, escitalopram, tricyclic antidepressants, buspirone
- Related products: antidepressants category, anti-parkinsonian category
- RXshop Editorial Team — reviewed by Thomas Walsh, MD, Psychiatry
Medical Disclaimer: The information in this article is for educational and informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek guidance from a qualified healthcare provider with any questions you may have regarding a medical condition, and before starting, stopping or changing any medication.