Concomitant use of monoamine oxidase inhibitor and tyrosine in parenteral nutrition

Monoamine oxidase inhibitors (MAOIs) prevent the breakdown of tyramine in the body, and can cause a sudden increase in blood pressure with significant tyramine build up. This phenomenon, when it occurs, is known as tyramine pressor response. It is unknown if tyrosine administered in parenteral nutrition (PN) leads to tyramine build-up with concomitant use of MAOIs. It is also unknown if PN patients who are taking MAOI are at risk for the tyramine pressor response. This is a theoretical possibility as tyrosine endogenously undergoes decarboxylation to produce tyramine. We describe our experience with a 67-year-old woman with severe depression who was on the MAOI, transdermal selegiline. Her clinical course was complicated by an inability to take adequate per oral (PO) intake and she met criteria for unspecified severe protein-calorie-malnutrition in the context of social or environmental circumstances. Therefore, she required PN initiation. Plenamine^TM (B. Braun, Bethlehem, PA, USA) was used as the amino acid source in the PN, which contains 39 mg of tyrosine per 100 ml of solution. The patient was monitored closely for any signs of hypertensive crisis while on PN and selegiline. She safely tolerated the combined therapy without any side effects. This is the first documented report of co-administration of PN containing tyrosine along with a MAOI. Our findings suggest that the dose of selegiline used in this patient can be co-administered safely in the setting of PN. However, further study is needed to verify our findings beyond this one patient. In conclusion, we recommend initiating PN and increasing it to goal in patients taking MAOIs, gradually, while monitoring for hypertensive crisis given the theoretical possibility of the tyramine pressor response.