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Tyramine: Effects and Interactions

Tyramine is a byproduct of tyrosine metabolism that causes the indirect release of catecholamines like norepinephrine from nerve terminals. It is normally inactive when taken orally due to metabolism by MAO in the liver. However, when MAO is inhibited by drugs, tyramine can be absorbed and cause a hypertensive crisis through indirect release of norepinephrine. Tyramine is found in foods like cheese, wine, and smoked meats, so patients on MAO inhibitors must restrict their intake to avoid dangerous drug interactions.

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67 views2 pages

Tyramine: Effects and Interactions

Tyramine is a byproduct of tyrosine metabolism that causes the indirect release of catecholamines like norepinephrine from nerve terminals. It is normally inactive when taken orally due to metabolism by MAO in the liver. However, when MAO is inhibited by drugs, tyramine can be absorbed and cause a hypertensive crisis through indirect release of norepinephrine. Tyramine is found in foods like cheese, wine, and smoked meats, so patients on MAO inhibitors must restrict their intake to avoid dangerous drug interactions.

Uploaded by

Zobayer Ahmed
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© © All Rights Reserved
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2018/03/22 07:43 1/2 Tyramine

Tyramine
● Drug Class: Indirectly Acting Sympathomimetic (a byproduct of tyrosine metabolism)
● Mechanism of Action:
❍Tyramine is taken up into nerve terminals by NET (the norepinephrine reuptake
transporter) and causes the release of catecholamines. It has been proposed that this
results from reverse transport of NET (Broadley, 2010).
❍The effects of tyramine are increased in the presence of MAO inhibitors. MAO present in nerve
terminals metabolizes both cytosolic amines, such as norepinephrine, as well as tyramine,
converting them to inactive metabolites. Normally the bioavailability of dietary tyramine (which is
present in red wine & cheese) is relatively low due to the high expression of MAO in the GI tract
and liver. However, when MAO is inhibited, high levels of tyramine can be absorbed, resulting
in a “hypertensive crisis” due to the indirect release of norepinephrine from nerve terminals.

● Pharmacokinetics:
❍Tyramine is readily metabolized by MAO in the liver and is normally inactive when taken orally
because of a high first-pass effect (low bioavailability).
❍If administered parentally, or if taken orally while taking MAO inhibitors, it produces
effects similar to norepinephrine, and can possibly cause a hypertensive crisis.
❍Tyramine causes the release of catecholamines from a small pool, and repeated exposure may
result in tachyphylaxis (a rapidly developing form of tolerance).
● Major drug Interactions:
❍Indirectly acting sympathomimetic amines must be taken up into the nerve terminal to promote

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release. Thus agents that inhibit the NET uptake pump (e.g. cocaine or imipramine)
antagonize responses to indirectly acting sympathomimetics.
❍Agents that cause depletion of catecholamines from the sympathetic nerve terminals (e.g.,
reserpine) can also antagonize indirectly acting agents (such as tyramine) because there is a lack
of catecholamines to be released. However, since catecholamine depletion takes some time to
develop, reserpine-like drugs must be given several hours to days in advance of tyramine for this
interaction to be observable.
● Note:
❍Tyramine is found in relatively high concentrations in fermented foods such as cheese,
sausage, pepperoni, salami, pickled or smoked fish & yeast supplements. Small
amounts are found in red wine & chicken liver as well; See Table 9-5 in ( Biaggioni & Robertson
(2012)).
● Reference:
❍Biaggioni I, Robertson D (2015): Adrenoceptor Agonists & Sympathomimetic Drugs (Chapter 9).
In: Basic and Clinical Pharmacology. 13th Ed. B Katzung, AJ Trevor (Editors); McGraw-Hill.
❍Broadley KJ (2010): The vascular effects of trace amines and amphetamines. Pharmacol Ther.
125(3):363-75. doi: 10.1016/j.pharmthera.2009.11.005.

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From:
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Last update: 2016/09/20 16:11

http://tmedweb.tulane.edu/pharmwiki/ Printed on 2018/03/22 07:43

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