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

• Antipsychotics -- includes butyrophenones (such as haloperidol) and phenothiazines (such as chlorpromazine, fluphenazine, and promethazine)
• Phenytoin -- a medication used for seizures
• Halothane -- a medication used during general anesthesia

Milk thistle may interfere with the following medications, because both milk thistle and these medications are broken down by the same liver enzymes:

• Allergy drugs -- such as fexofenadine (Allegra)
• Drugs for high cholesterol -- such as lovastatin (Mevacor, Altocor)
• Anti-anxiety drugs -- including alprazolam (Xanax), diazepam (Valium), and lorazepam (Ativan)
• Antiplatelet and anticoagulant drugs (blood thinners) -- including clopidogrel (Plavix) and warfarin (Coumadin)
• Some cancer drugs