Warning: Chemo drugs and antidepressants may interact with certain foods

Warning: Chemo drugs and antidepressants may interact with certain foods
Monoamine Oxidase Inhibitors, (MAOIs), including chemo drugs such as Procarbazine and antidepressants such as Marplan, sometimes taken by patients during chemo, can conflict with foods such as eggs, fermented foods and dried meats; these antidepressants are even being considered as off-label anti-cancer drugs! 
 
This article has been updated several times since first posted in 2013.
 
Some chemo drugs are Monoamine Oxidase Inhibitors
 
My daughter had a brain tumour. After Temozolomide failed, she was given a triple drug, PCV. What doesn’t appear to have been mentioned at the time is that one of the three drugs may have significant and negative interactions with certain foods – and these must be avoided.
 
The P in PCV stands for Procarbazine, which is a monoamine oxidase inhibitor (MAOI).
 
Monoamine oxidase (MAO) is an enzyme in the gut which controls excess serotonin, dopamine and other 'feel good chemicals'. if you make too much of them. Not suprisingly, MAOI drugs (that inhibit MAO) are typically used as anti-depressants, where the Medical aim is to increase your feel good factor, and so the task is to inhibit the inhibitor.

MAOIs with the wrong foods can cause high blood pressure 

MAO also controls and inactivates excess tyramine, a 'trace' amino acid, when this reaches certain levels (1).

However, tyramine is found in a large number of foods. If MAO is inhibited by MAOI drugs, and you consume tyramine-rich foods, you can have excessive levels of tyramine suddenly present in the body and, especially the brain. Drugs like Procarbazine and anti-depressants with their MAOI content block the inactivation of excess tyramine, so if you eat those foods while taking an MAOI, you are in for trouble.  ‘Adverse and serious events' is the official term. For example, one effect is a rapidly raised blood pressure. There are a lot of foods on the danger list!

Wikipedia talks of MAOI drugs as being ‘last resort’ drugs because of these food interactions.

Many cancer patients also take anti-depressants

Marplan (isocarboxazid), Nardil (phenelzine), Emsam (selegiline), and Parnate (tranylcypromine) are MAOI drugs prescribed for depression. The Mayo Clinic wans that these anyway may interact with pain medications, other antidepressants and cardiovascular drugs, These can prompt dangerously high levels of serotonin.

I have yet to find a single cancer patient who has been put onto anti-depressants (more common than you would imagine), who has been warned of the dangers of certain foods or other drugs.

Monoamine Oxidase Inhibitors - now being repurposed to fight cancer

But it gets worse.

MAOI antidepressant drugs are being studied as repurposed, off-label drugs to treat cancer. They have already been shown to stop cancer development, growth and metastasis by targeting monoamine oxidase.

For example, they have been shown capable of targeting tumours in mice (2). 

They have been shown to activate tumour associated macrophages (3)

They have been shown capable of treating prostate cancer, especially androgen dependent cancer (4).

And they are being studied along side immunotherapy which unblocks T-cells (Pembrolizumab and Nivolumab) (5).

So these 'Last resort' drugs could about to become more widespread.

MAOI Drug adverse reactions can include:

•        Elevation of blood pressure, headaches, chest pains 
•        Diaphoresis (perspiration associated with fever), palpitations.
•        In severe cases, the crisis can result in intracranial hemorrhage,
        cardiac arrhythmias and cardiac failure.
 
Tyramine-rich foods to avoid:
 
Perhaps the most common foods that should be avoided are eggs, cheese, dried meats, pickled foods, alcohol, sauerkraut and kefir. 
 
A larger list includes - 
 
Eggs; Ginseng; Fermented foods, soy, sauerkraut and Kefir, all aged and mature cheeses like cheddar, Swiss blue cheese, mozzarella, parmesan, Romano, cheese spreads, cheese casseroles or any foods made with cheese’ yeasts (Brewers yeasts, marmite etc); all smoked, aged, pickled, fermented, or marinated meats, such as pickled herring, prawn/shrimp paste, smoked salmon, meat extracts, liver, game, dry sausages, pate, dried meats, bacon and ham; over-ripe fruit,; some beans; condiments and sauces (like soy sauce); packaged soups; all alcohol including beers, wine etc.
 
Monoamine Oxidase Inhibitor drugs and immunotherapy
 
While only a few cancer drugs currently act as MAO Inhibitors, if these start to be used with immunotherapy, or as general repurposed drugs, a lot more caution over diet will be needed.
 
Equally for those cancer patients with anxiety or depression, it is important to see whether your drug is a MAOI. It could explain some of the sudden food allergies we are seeing and it may explain why some patients seemingly have really bad reactions to the chemotherapy; it could not be the chemo but the drug they are taking for anxiety.
 
For the record, we have previously covered drugs that interact with the juice of grapefruit,  pomelos and large Seville oranges.

Go to: Chemo drugs, statins and others that interact with Grapefruit juice

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References
 
1. Wikipedia - tyramine - https://en.wikipedia.org/wiki/Tyramine
2 Drug commonly used as antidepressant helps fight cancer in mice - UCLA Newsroom - https://newsroom.ucla.edu/releases/antidepressant-immune-system-fight-cancer-mice
3. Targeting monoamine oxidase A-regulated tumor-associated macrophage polarization for cancer immunotherapy -  Nat Commun. 2021; 12: 3530.- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8192781/
4. Effect of Monoamine oxidase A (MAOA) inhibitors on androgen-sensitive and castration-resistant prostate cancer cells - Prostate, 2019 May;79(6):667-677
6. Targeting monoamine oxidase A for T cell-based cancer immunotherapy - Sci Immunol; 2021 May 14;6(59)
2022 Research
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