Brain with tyrosine molecule and medication pills

L-Tyrosine and Phenelzine: What You Need to Know About This Controversial Combination

Avery Sinclair in Health & Wellness December 2025 • 4 min read.

"Uncover the truth behind L-tyrosine and phenelzine: separating fact from fiction in mental health treatments."

In the world of mental health treatment, the interaction between medications and supplements is a critical area of consideration. One such interaction that has sparked considerable debate involves the use of L-tyrosine, a naturally occurring amino acid, alongside phenelzine, a potent antidepressant. Phenelzine, known by its brand name Nardil®, belongs to a class of drugs called monoamine oxidase inhibitors (MAOIs).

The concern arises from the prescribing information for phenelzine, which cautions against the use of sympathomimetic substances and related compounds, including L-tyrosine, due to the risk of hypertensive crisis—a severe and potentially life-threatening increase in blood pressure. This warning has led many healthcare providers and patients to avoid combining these two substances.

However, a closer look at the scientific literature reveals a more nuanced picture. This article aims to explore the available evidence, separating anecdotal warnings from evidence-based research, to provide a clearer understanding of the potential risks and benefits of combining L-tyrosine and phenelzine.

The Hypertensive Crisis Question: Does L-Tyrosine Really Pose a Risk?

Brain with tyrosine molecule and medication pills

The primary concern surrounding the combination of L-tyrosine and phenelzine is the potential for hypertensive crisis. Phenelzine, as an MAOI, inhibits the enzyme monoamine oxidase, which is responsible for breaking down neurotransmitters like dopamine, norepinephrine, and serotonin. This inhibition leads to increased levels of these neurotransmitters in the brain, which can improve mood and reduce symptoms of depression. However, it also means that other substances that affect these neurotransmitters, such as tyramine, can have a more pronounced effect.

Tyramine, found in aged cheeses, fermented foods, and certain alcoholic beverages, is known to cause a surge in blood pressure. The prescribing information for phenelzine warns against consuming tyramine-rich foods to avoid hypertensive crisis. But what about L-tyrosine? Here’s where the controversy lies.

The Claim: Phenelzine's prescribing guidelines specifically mention L-tyrosine as a substance to avoid, suggesting it could lead to hypertensive crises.
The Research: Extensive literature reviews, including searches of Google Scholar and PubMed, have found no documented cases of hypertensive crisis directly linked to L-tyrosine when taken with phenelzine.
Contradictory Evidence: Some studies even suggest that L-tyrosine may help lower blood pressure, contrary to the warning.

The original article points out that the warning against L-tyrosine appears to lack a solid scientific foundation. While tyramine's role in hypertensive crises with MAOIs is well-established, the same cannot be said for L-tyrosine. This raises questions about the validity of the warning and whether it is based on outdated information or theoretical risks rather than actual evidence.

The Bottom Line: Informed Decisions and Open Communication

The interaction between L-tyrosine and phenelzine remains a complex and somewhat controversial topic. While the prescribing information for phenelzine advises against the use of L-tyrosine, current research and clinical experience suggest that the risk of hypertensive crisis may be overstated. As always, consult with healthcare professionals.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.2147/cpaa.s67271, Alternate LINK

Title: Administration Of Supplemental L-Tyrosine With Phenelzine: A Clinical Literature Review

Subject: Pharmacology (medical)

Journal: Clinical Pharmacology: Advances and Applications

Publisher: Informa UK Limited

Authors: Marty Hinz, Alvin Stein, Ted Cole, Patricia Ryan

Published: 2014-07-01

Everything You Need To Know

What is the primary concern when combining L-tyrosine and phenelzine?

The main concern revolves around the potential for hypertensive crisis, a severe and dangerous increase in blood pressure. Phenelzine, an MAOI, inhibits the breakdown of neurotransmitters, increasing their levels. The prescribing information for phenelzine cautions against using sympathomimetic substances, including L-tyrosine, due to this risk. However, research has not consistently supported this warning, leading to debate about its validity.

Why does phenelzine's prescribing information warn against combining it with substances like L-tyrosine?

Phenelzine, an MAOI, prevents the breakdown of neurotransmitters like dopamine, norepinephrine, and serotonin. This increases the levels of these neurotransmitters in the brain, which can improve mood but also makes the user susceptible to hypertensive crisis. The prescribing information cautions against substances that could further elevate these neurotransmitter levels, such as L-tyrosine, due to the theoretical risk of a dangerous surge in blood pressure. The caution is similar to the one with Tyramine, which is found in aged cheeses, fermented foods, and certain alcoholic beverages.

Has research confirmed the risk of hypertensive crisis when combining L-tyrosine and phenelzine?

Despite the warnings in phenelzine's prescribing information, extensive research reviews, including searches of Google Scholar and PubMed, have not found documented cases of hypertensive crisis directly linked to combining L-tyrosine and phenelzine. Some studies even suggest that L-tyrosine might help lower blood pressure. This lack of empirical evidence raises questions about the scientific basis of the warning and whether it is based on outdated information or theoretical risks.

What is the role of monoamine oxidase inhibitors (MAOIs) like phenelzine in the context of neurotransmitters?

MAOIs, such as phenelzine (Nardil), function by inhibiting the monoamine oxidase enzyme, which is responsible for breaking down neurotransmitters like dopamine, norepinephrine, and serotonin. By inhibiting this enzyme, phenelzine increases the levels of these neurotransmitters in the brain. This elevation can alleviate symptoms of depression but also requires careful management of dietary intake and other substances to avoid potential interactions, such as hypertensive crisis.

Given the controversy, what's the best approach when considering combining L-tyrosine and phenelzine?

The interaction between L-tyrosine and phenelzine is complex, and the risk of hypertensive crisis may be overstated. However, it's critical to make informed decisions based on the available evidence and guidance from healthcare professionals. Open communication with a doctor or qualified healthcare provider is essential to assess individual risks and benefits. They can provide personalized recommendations based on your specific health condition and medication regimen. Further, this ensures monitoring of blood pressure and overall health.