Maoi Interactions

Monoamine oxidase inhibitors block MAO-A in the gut and liver, the enzyme that normally breaks down dietary tyramine. Unmetabolized tyramine triggers a surge of stored norepinephrine, which can produce a hypertensive crisis (the 'cheese reaction') with severe blood pressure spikes, headache, and in serious cases stroke or death.

St. John's Wort raises brain serotonin, norepinephrine, and dopamine through reuptake inhibition and shows weak monoamine oxidase inhibition. Layered on a prescription MAOI, which blocks the breakdown of those same monoamines, the combination can push monoamine signaling to dangerous levels and is contraindicated because of the risk of serotonin syndrome and hypertensive crisis.

5-HTP is the direct precursor to serotonin and bypasses the rate-limiting step of serotonin synthesis. Combined with an MAOI, which blocks serotonin breakdown, serotonin can rise to dangerous levels and trigger serotonin syndrome, a potentially life-threatening reaction.