Administration of supplemental L-tyrosine with phenelzine: a clinical literature review

The subject of this literature review is the alleged relationship between L-tyrosine, phenelzine, and hypertensive crisis. Phenelzine (Nardil(®)) prescribing information notes: "The potentiation of sympathomimetic substances and related compounds by MAO inhibitors may result in hypertensive crises (see WARNINGS). Therefore, patients being treated with NARDIL should not take […] L-tyrosine […]". Interest in the scientific foundation of this claim was generated during routine patient care. A comprehensive literature search of Google Scholar and PubMed revealed no reported cases of hypertensive crisis associated with concomitant administration of L-tyrosine and phenelzine. Review of current US Food and Drug Administration nutritional guidelines relating to ongoing phenelzine studies reveals no mention and requires no consideration of L-tyrosine ingestion in combination with phenelzine. This paper is intended to provide an objective review of the science to then allow the reader to formulate the final opinion.