If you are currently being treated with any of the following medications, you should not use brewer's yeast without first talking to your healthcare provider.

Monoamine Oxidase Inhibitors (MAOIs) -- Brewer's yeast contains a large amount of tyramine, a substance that can interact with MAOIs and cause a hypertensive crisis. A hypertensive crisis is characterized by a rapid and dangerous rise in blood pressure that can cause heart attack or stroke. MAOIs are used to treat depression and include

• Phenelzine (Nardil)
• Tranylcypromine (Parnate)
• Selegiline (Ensam, Eldepryl)
• Isocarboxazid (Marplan)

Meperidine (Demerol) -- As with MAOI antidepressants, brewer's yeast may also lead to hypertensive crisis if taken with Demerol, a narcotic medication used to relieve pain.