Milk Thistle Side Effects, Interactions and Warnings

Milk Thistle
Side Effects, Interactions and Warnings





  • Milk thistle (Silybum marianum) is a popular herbal product used for hepatoprotection and chemoprevention. Two commercially available formulations are the crude extract, silymarin, and the semipurified product, silibinin. Observations in this study prompt clinical evaluation of a potential warfarin – milk thistle interaction.
    – Two flavonolignans from milk thistle (Silybum marianum) inhibit CYP2C9-mediated warfarin metabolism at clinically achievable concentrations. — Brantley SJ, Oberlies NH, Kroll DJ, Paine MF. — J Pharmacol Exp Ther. 2010 Mar;332(3):1081-7. Epub 2009 Nov 24.

  • Milk thistle increases bile flow and secretion which can result in loose stools.

    – Murray, M. — The Pill Book Guide to Natural Medicines: Vitamins, Minerals, Nutritional Supplements, Herbs, and Other Natural Products. — Bantam, 2002. 743.

  • Milk thistle has the potential to modulate cytochrome P450 activity and thus participate in interactions with conventional drugs.
    – Xenobiotica 2002 Jun;32(6):451-78 — Pharmacokinetic interactions between herbal remedies and medicinal drugs. — Ioannides C.

  • Adverse and possibly violent reactions have been reported such as intermittent episodes of sweating, nausea, colicky abdominal pain, fluid diarrhea, vomiting, weakness and collapse.
    – Med J Aust 1999 Mar 1;170(5):218-9 — An adverse reaction to the herbal medication milk thistle (Silybum marianum). Adverse Drug Reactions Advisory Committee.














last update: February 2014



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