"Aggregator" MAO Inhibitors


MAO (Monoamine Oxidase) Inhibitor Herbs

Compounds in these herbs have been shown experimentally to have varying degrees of monoamine oxidase (MAO) inhibition. MAO enzymes degrade catecholamine neurotransmitters, e.g., serotonin, dopamine, epinephrine and norepinephrine. MAO inhibitors directly or indirectly increase catecholamine levels. Dietary intake of amines such as tyramine must be restricted in MAOI therapy.

Physiological MAOI effects at therapeutic dose levels of herbs with in vitro MAOI activity are unlikely. Interaction with pharmaceutical MAOI drugs, as well as other drugs affecting catecholamine metabolism can be considered at least a theoretical possibility, although in practice, adverse effects during MAOI therapy from herbs are more likely to result from concurrent use of herbs in the symapathomimetics group.

For discussion of issues surrounding putative MAOI interactions see Hypericum perforatum (St. John's Wort).

overview of interactions:
• herbs theoretically affecting drug toxicity: Monoamine Oxidase Inhibitors

herbs theoretically affecting drug toxicity: Epinephrine

herbal concerns: Sympathomimetic Herbs

herbal concerns: Vasoconstrictor Herbs

herbal concerns: Sedative Herbs

herbal concerns: Xanthine-containing Herbs


herbs theoretically affecting drug toxicity: Monoamine Oxidase Inhibitors

• mechanism: Monoamine oxidase inhibitor herbs theoretically may additively synergize with MAOI drugs which would cause further elevated catecholamine levels and possible hypertension. Conclusive evidence is lacking.

herbs theoretically affecting drug toxicity: Epinephrine

• mechanism: Monoamineoxidase inhibiting herbs may theoretically potentiate adrenomimetic drugs which would cause further elevated catecholamine levels and possible hypertension.

herbal concerns:
Indirect interaction with other herbs from the following groups may take place through various physiologic mechanisms:
Sympathomimetic Herbs
Vasoconstrictor Herbs
Sedative Herbs
Xanthine-containing Herbs

Common herbs with MAO inhibitor activity according to experimental data:
Hypericum perforatum (St John's Wort)
• Passiflora incarnata (Passion Flower)
Glycyrrhiza glabra (Licorice Root)
• Myristica fragrans (Nutmeg)

Restricted or unusual herbs with MAO inhibitor activity:
• Lophophora spp. (Peyote)
• Peganum harmala (Syrian Rue)

Cytisus scoparius (Scotch Broom) contains <2% tyramine, a nutrient which is catabolized by MAO. In physiological terms, the bradycardic and hypertensive actions of sparteine in Cytisus are more likely to interact with MAOI drugs than the tyramine content.

Pausinystalia yohimbe (Yohimbe) has a very weak in vitro MAOI activity. It is however hypertensive due to central adrenergic antagonism, increasing peripheral sympathetic outflow, and may be contraindicated with MAOI's.

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Do not rely solely on the information in this article.

The information presented in Interactions is for informational and educational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, case reports, and/or traditional usage with sources as cited in each topic. The results reported may not necessarily occur in all individuals and different individuals with the same medical conditions with the same symptoms will often require differing treatments. For many of the conditions discussed, treatment with conventional medical therapies, including prescription drugs or over-the-counter medications, is also available. Consult your physician, an appropriately trained healthcare practitioner, and/or pharmacist for any health concern or medical problem before using any herbal products or nutritional supplements or before making any changes in prescribed medications and/or before attempting to independently treat a medical condition using supplements, herbs, remedies, or other forms of self-care.


Brinker F. Herb Contraindications and Drug Interactions. Second edition., Sandy, OR: Eclectic Institute Inc, 1998.

Hardman J, et al. (eds.) Goodman &Gilman's Pharmacological Basis of Therapeutics. Ninth Edition. McGraw Hill, 1996.

McGuffin M, et al. (eds.) AHPA Botanical Safety Handbook . CRC Press, 1997.

Newall C, Anderson L, Phillipson JD, Herbal medicines: A Guide for Health-Care Professionals. London: Pharmaceutical Press, 1996.