Final answer:
Consuming high-tyramine foods while on MAOIs like phenelzine can lead to a hypertensive crisis due to the inhibited breakdown of tyramine, which excessively increases blood pressure.
Step-by-step explanation:
If a patient taking an MAOI like phenelzine consumes foods high in tyramine, such as aged meats and cheeses, they could experience a hypertensive crisis. This occurs because MAOIs inhibit the breakdown of neurotransmitters, and tyramine is a substrate of monoamine oxidase. When MAOIs prevent the breakdown of tyramine, its levels can rise excessively, leading to severe increases in blood pressure as tyramine prompts the release of noradrenaline (norepinephrine), which is a vasoconstrictor. The symptoms of a hypertensive crisis may include headache, tachycardia, nausea, increased blood pressure, and in severe cases, stroke or cerebral hemorrhage. Avoiding high-tyramine foods and being aware of drug and food interactions are critical for patients taking MAOIs.