MAOI plus tyramine: the hypertensive crisis (cheese effect)

Why the diet is required

Tyramine is a naturally occurring pressor amine that accumulates in fermented, aged, or spoiled foods through bacterial decarboxylation of tyrosine. Under normal circumstances, MAO-A in the gut wall and liver metabolizes ingested tyramine before it reaches systemic circulation.

MAOIs inhibit MAO-A (phenelzine, tranylcypromine, isocarboxazid inhibit both A and B; selegiline is selective for MAO-B at low doses but hits MAO-A at higher doses). When MAO-A is inhibited, dietary tyramine reaches the systemic circulation.

Tyramine displaces norepinephrine from presynaptic sympathetic nerve terminals, causing an acute massive release of norepinephrine. This produces sudden severe hypertension, headache, palpitations, chest pain, and in severe cases stroke or death.

The threshold dose for hypertensive crisis is roughly 6 to 25 mg of tyramine in a single meal. Aged cheddar can contain 1,500 mg per kilogram. A single serving can exceed the threshold substantially.

The food list

Absolutely avoid:

• Aged and mature cheeses (cheddar, brie, camembert, gouda, gruyere, parmesan, roquefort, stilton, mozzarella if aged)
• Cured, aged, or fermented meats (salami, pepperoni, prosciutto, mortadella, aged beef, aged sausage)
• Tap beer, unpasteurized beer, some craft beers
• Aged/fermented soy products (miso, soy sauce, soybean paste, tempeh, aged tofu)
• Sauerkraut, kimchi
• Marmite, Vegemite
• Fava beans (also contain L-dopa, adding to problem)
• Overripe or spoiled fruit
• Air-dried or aged fish

Usually safe in moderation:

• Fresh cheese (cottage cheese, cream cheese, ricotta, fresh mozzarella)
• Fresh meats
• Bottled and canned beer in moderation (12 oz per day acceptable)
• Fresh soy products, plain tofu
• Fresh fruit (except overripe)
• Wine in moderation (though older red wines have higher tyramine)

Common misconceptions (not actually problematic):

• Fresh coffee (early lists included coffee; not clinically significant)
• Chocolate (contains phenylethylamine, not tyramine; rarely problematic)
• Fresh bread and pastries with yeast (baker's yeast is heat-killed, contains minimal tyramine; brewer's yeast supplements are a different story)

Drug interactions with MAOIs

Beyond dietary tyramine, MAOIs interact with many drugs:

Sympathomimetics (cause hypertensive crisis):

• Pseudoephedrine (Sudafed)
• Phenylephrine (Sudafed PE, many OTC decongestants)
• Ephedrine
• Amphetamines (Adderall, Vyvanse, methamphetamine)
• Methylphenidate (some risk)
• Cocaine
• MDMA

Serotonergic drugs (cause serotonin syndrome):

• SSRIs and SNRIs
• Tramadol
• Meperidine (historical high-mortality combination)
• Dextromethorphan at higher doses
• St. John's wort
• Triptans (theoretical risk; clinical significance debated)
• Linezolid, methylene blue (weak MAOIs themselves)

Other:

• Buspirone (case reports of hypertension)
• Levodopa (hypertensive crisis)
• Tetrabenazine (VMAT2 inhibitor; complex interaction)

The selegiline transdermal exception

Selegiline transdermal (Emsam) at 6 mg per 24 hours is FDA-approved for depression without a dietary tyramine restriction. The mechanism: transdermal delivery bypasses gut and liver first-pass, so gut MAO-A remains functional to metabolize dietary tyramine before it reaches systemic circulation. Brain MAO inhibition is sufficient for antidepressant effect.

At 9 mg and 12 mg per 24 hours, some dietary caution is advised, though full restriction is still not required in most guidance.

Selegiline transdermal is one of the more usable MAOIs in modern practice for this reason. It comes at a cost (higher than oral MAOIs and than most other antidepressants).

Managing a hypertensive crisis

Signs: sudden severe occipital headache, sweating, palpitations, tachycardia (though sometimes reflex bradycardia), chest pain, nausea, blurred vision, elevated BP (often above 180/120).

Emergency treatment:

• IV phentolamine (alpha-blocker) is the classic antidote
• Nitroprusside for rapid BP control
• Nicardipine or clevidipine also work
• Avoid propranolol alone (unopposed alpha stimulation can worsen)

Some patients used to be given oral nifedipine to bite through for at-home emergency management, but this is not recommended anymore because of the risk of precipitous hypotension.

Common questions

Are MAOIs still used? Yes, though rarely as first-line. MAOIs are effective for treatment-resistant depression, atypical depression, panic disorder with atypical features, and PTSD. Selegiline transdermal is more usable than oral MAOIs because of the reduced dietary restriction. Referral to a psychiatrist experienced with MAOIs is typically required.

Can I ever have cheese on an MAOI? Yes, fresh cheeses (cottage cheese, cream cheese, ricotta, fresh mozzarella) are usually safe. Aged cheeses are the ones to avoid. When in doubt, check the tyramine content.

Can I drink alcohol on an MAOI? In moderation, wine and non-tap beer are usually acceptable. Tap beer, unpasteurized craft beer, and heavy alcohol use are not. Red wine has more tyramine than white; older reds more than younger.

What about decongestants for a cold? Avoid pseudoephedrine and phenylephrine entirely. Alternatives for nasal congestion: saline spray, humidifier, first-generation antihistamine (though sedating), nasal steroid spray (fluticasone).

Can I take dextromethorphan cough syrup on an MAOI? No. Dextromethorphan is serotonergic and can precipitate serotonin syndrome with MAOIs. Alternative cough management: honey, humidifier, guaifenesin (which is not serotonergic).

How long after stopping an MAOI can I start an SSRI? 14 days. Do not overlap.

How long after stopping fluoxetine can I start an MAOI? 5 weeks. Fluoxetine's active metabolite norfluoxetine has a long half-life and takes weeks to clear.

Is selegiline patch really that different? Yes for the dietary restriction. At 6 mg per 24 hours, patients do not need to follow the low-tyramine diet. Prescription drug interactions still apply (same list as oral MAOIs). It's genuinely more usable.

What if I accidentally eat aged cheese on an MAOI? Watch for symptoms of hypertensive crisis for the next 2 to 4 hours. If you develop severe headache, palpitations, or chest pain, go to the ED. Most single accidental exposures produce no reaction, but severity is unpredictable.

Sources

• Blackwell B. Adverse effects of antidepressant drugs, part 1: monoamine oxidase inhibitors and tricyclics. Drugs. 1981;21(3):201-219.
• Shulman KI, Herrmann N, Walker SE. Current place of monoamine oxidase inhibitors in the treatment of depression. CNS Drugs. 2013;27(10):789-797.
• Culpepper L. Reducing the burden of difficult-to-treat major depressive disorder: revisiting monoamine oxidase inhibitor therapy. Prim Care Companion CNS Disord. 2013;15(5).
• FDA prescribing information for phenelzine, tranylcypromine, isocarboxazid, and selegiline.
• Wimbiscus M, Kostenko O, Malone D. MAO inhibitors: risks, benefits, and lore. Cleve Clin J Med. 2010;77(12):859-882.