PsychoTropical Research - Dr Ken Gillman, Serotonin Syndrome, Mirtazapine, Dual Action Drugs. MAOIs - Tyramine.

PsychoTropicalResearch, serotonin and serotonin syndrome research.

MAOIs - Tyramine

MAOIs - Tyramine

Date Created: 15/11/1999   Last Modified: 06/10/2002   Last Checked: 17/04/2004

Tyramine and blood pressure: the current evidence

The 'TYR 30' test measures the amount of tyramine necessary to raise the systolic blood pressure by 30 mm Hg. In people not taking MAOIs between 200 and 800 mg of tyramine must be consumed to raise systolic blood pressure by 30 mm Hg. The TYR 30 is greatly decreased by MAOIs, ie much lesser amounts of tyramine are needed to raise BP by 30 mm Hg.

One piece of research estimated that approximately seven times less tyramine will do this with moclobemide and about fifty times less with tranylcypromine.

In a group of healthy human volunteers the TYR 30 in those taking moclobemide (at a dose of 600 mg per day) was about 300 mg of tyramine and on tranylcypromine (at a dose of 30 mg per day) was around 35 mg of tyramine. This suggests that while on tranylcypromine 30 mg per day 25-50 mg of tyramine will raise the BP by around 30 mm Hg; but probably not raise it to a dangerous level. The tranylcypromine dose used in this study is lowish; it would be useful to have data relating to a dose of tranylcypromine of 50 mg per day.

However the extent of the variability in a large population sample has never been tested. It is important to remember that there may be some people who experience larger BP increases.

It may be assumed (and this is supported by evidence) that rapid absorption (on an empty stomach) will give higher peak levels of tyramine and a greater elevation of blood pressure than the same amount taken as part of a full meal. This probably explains why quite a small amount of beer on an empty stomach can produce reactions; in such circumstances people are probably two to five times more sensitive to tyramine. Tyramine in liquids taken on an empty stomach should be regarded as a separate issue.

For tyramine taken as food in a normal meal the limited data suggest that up to 25 mg is unlikely to cause serious (see below) hypertension in most individuals. To keep below 25 mg of tyramine one could eat about 50 grams of the most potent cheese, or 25 mls of soy sauce. However some data suggests that as little as 5-10 mg of tyramine may be sufficient to produce hypertension and headache in some individuals.

There has been little discussion about the degree of risk of actual morbidity or mortality from cerebro-vascular incidents in relation to the severity of hypertension that might be generated. It may be relevant to note that many common activities regularly produce BP elevations in excess of those reported (and regarded as 'dangerous') by psychiatrists. These include exertion, coitus, weight-lifting etc. Systolic BPs of 300-400 are often generated in weight lifting; but we have no discussion of banning it from the Olympics (although CVAs have been documented).

Lastly, a reminder:-- provided action is taken if tyramine is ingested then hypertension can be prevented. This should be feasible in most cases and is likely to obviate the risk of harm occurring.

The following list gives an indication of likely tyramine levels for relevant substances

  • A selection of 43 soft and hard cheeses:-- up to 60 mg per 100 grams (600 mg per kilo)
  • Soy sauce:-- Maximum:-- 940 mg per litre (approx 1 mg per ml). Most samples measured have ranged between 10-200 mg per litre
  • Soy bean products,
  • 'tofu':-- fresh, less than 1 mg per 100 grams
  • 'tofu':-- 7 days refrigerated, 16 mg per 100 grams
  • 'Soya bean curd':-- fresh, less than 1 mg per 100 grams
  • 'Soya bean curd':-- 7 days refrigerated, less than 1 mg per 100 grams
  • 'miso' soup etc. max ~ 100 mg per 100 ml

  • 'Keg' or 'tap' beers:-- 25 to 100 mg per litre
  • Bottled beers:-- 10 mg per litre
  • Air-dried sausage:-- 25 mg per 100 grams
  • Fish products:-- up to 16 mg per 100 grams
  • Ripe banana peel:-- 6.5 mg per 100 grams
  • Protein extracts:-- three brands of meat extract contained 10, 20 and 30 mg per 100 grams
  • Sauerkraut:-- varies from 2 to 10 mg per 100 grams
  • Raw fish up to 2.6 mg per 100 grams

100 grams of cheese is a piece approx 6 x 6 x 3 cms (look at a standard 100 g pack of butter next time you have the chance to get a clear mental picture of how big a piece that is).

50 mg of tyramine per 100 grams of the strongest cheese is the max likely concentration

25 mg of ingested tyramine as the minimum than is capable of inducing a dangerous blood pressure increase.

It follows that the approx worst case scenario is that 50 grams of a very strong cheese could possibily produce a potentially dangerous reaction: ie a piece 6 x 3 x 3 cms in size.