Phenelzine is a member of a group of drugs called monoamine oxidase (MAO) inhibitors (also called MAOIs). Phenelzine is sometimes used to treat people with depression who do not respond to other antidepressant drug therapy.
Phenelzine has a chemical structure similar to other drugs (isoniazid and hydralazine) that can cause vitamin B6 deficiency. One case of phenelzine-induced vitamin B6 deficiency has been reported.1 Little is known about this interaction. People taking phenelzine should ask their doctor about monitoring vitamin B6 levels and considering supplementation.
Scotch broom contains high levels of tyramine. Combining phenelzine and Scotch broom may cause MAOI-type reactions (diarrhoea, flushing, sweating, pounding chest, dangerous changes in blood pressure, and other symptoms).2 It is important for people taking phenelzine to avoid Scotch broom. People with questions about phenelzine and Scotch broom should ask their doctor.
Two cases were reported involving men treated with phenelzine who experienced restlessness, agitation, tremor, and insomnia after drinking large quantities of cola beverages containing aspartame.3 Until more is known, people taking phenelzine should use aspartame-containing foods with caution.
Ephedra contains the chemical ephedrine, which may interact with phenelzine, causing potentially dangerous changes to blood pressure.4 People should read product labels for ephedra/ephedrine content. Ephedra and ephedrine-containing products should be avoided during phenelzine therapy. People with questions about phenelzine and ephedra/ephedrine should ask their doctor or pharmacist.
Although St. John’s wort contains chemicals that bind MAO in test tubes, it is believed that the action of St. John’s wort is not due to MAOI activity.5 However, because St. John’s wort may have serotonin reuptake inhibiting action (similar to the action of drugs such as Prozac®, it is best to avoid concomitant use of St. John’s wort with MAOI drugs.
Phenelzine can alter metabolism of a chemical called tyramine that is present in certain foods, leading to diarrhea, flushing, sweating, pounding chest, dangerous changes in blood pressure, and other symptoms.6 It is important for people taking phenelzine to avoid tyramine-containing foods. People with questions about phenelzine and tyramine-containing foods should ask their doctor or pharmacist.
1. Heller CA, Friedman PA. Pyridoxine deficiency and peripheral neuropathy associated with long-term phenelzine therapy. Am J Med 1983;75:887–8.
2. Brinker F. Interactions of pharmaceutical and botanical medicines. J Naturopathic Med 1997;7(2):14–20.
3. Shader RI, Greenblatt DJ. Phenelzine and the dream machine-ramblings and reflections. J Clin Psychopharmacol 1985:5:65.
4. Threlkeld DS, ed. Central nervous system drugs, antidepressants, monoamine oxidase inhibitors. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Apr 1997, 264y.
5. St. John’s wort, Hypericum perforatum. In American Herbal Pharmacopoeia and Therapeutic Compendium, ed. R Upton. Santa Cruz, CA: AHP, 1997.
6. Threlkeld DS, ed. Central Nervous System Drugs, Antidepressants, Monoamine Oxidase Inhibitors. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Apr 1997, 264y.
Last Review: 11-07-2012
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