Milk thistle may affect CYP3A4 or UGT drug handling, although human findings are inconsistent. Case reports and clinical observations raise more specific concerns with sirolimus, warfarin, and some antipsychotic medicines.

Use with caution. Healthcare professional review recommended before use.

Contraindications

Known allergy to ragweed, daisies, chrysanthemums, marigolds, or related plants

Cautions

Digestive effects such as bloating, nausea, and gas are the most common reported problems.
Product quality varies, and some supplements do not contain the labeled amount of silymarin.
Pregnancy and breastfeeding safety are not well established.

Drug Interactions

Drug Class / Substrate	Mechanism	Severity	Source
Sirolimus	Milk thistle may reduce sirolimus clearance and increase adverse effects.	Major	Memorial Sloan Kettering About Herbs
Warfarin	A case report described increased INR after a liver-cleanse product containing milk thistle.	Moderate	Memorial Sloan Kettering About Herbs
Haloperidol and risperidone	Pancreatitis cases were reported with concurrent use.	Major	Memorial Sloan Kettering About Herbs
CYP3A4 and UGT substrate medicines	Laboratory findings suggest altered metabolism, but CYP3A4 results in humans are conflicting.	Uncertain	Memorial Sloan Kettering About Herbs

This information is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before using herbal medicines, especially if you take prescription medications.