Information on Milk Thistle Interactions

Milk thistle herbal supplements are promoted for numerous conditions, but primarily as a complementary treatment for liver problems, particularly hepatitis C and cirrhosis of the liver related to alcoholism. The active constituent in this herb, silymarin, is believed to protect the liver from dangerous toxins, according to the University of Maryland Medical Center. Although considered generally safe, milk thistle can interact with some medications.

Milk Thistle Classification

The U.S. Food and Drug Administration classifies herbal supplements, also known as botanicals, as dietary supplements, according to the National Center for Complementary and Alternative Medicine. What's important to know about dietary supplements is that the company that makes them doesn't have to submit proof that it is safe or effective. Milk thistle products don't go through the same rigorous approval by the FDA as do products that are classified as medications. The FDA does monitor the safety of these products, says NCCAM, and if a product is unsafe, it can be taken off of the market. Herbal supplements may seem a safer bet, as they're often marketed as "all natural." However, they can interact with other drugs and supplements that you're taking, cautions NCCAM, and cause adverse effects.

Problems with Milk Thistle

Research shows that milk thistle can interact with any medication that is metabolized by a liver enzyme known as cytochrome P-450 3A4, according to the Memorial Sloan-Kettering Cancer Center. Milk thistle may inhibit how this enzyme processes the medication, resulting in higher levels of the medication in your blood. Increased adverse reactions associated with the medication and even toxicity can result. If you're taking medications that are processed by cytochrome P450 3A4, make sure to speak with your doctor before taking this supplement, cautions the center.

Medications to Avoid

Medications to avoid that are metabolized by cytochrome P450 3A4 include allergy drugs that include fexofenadine, notes the University of Maryland Medical Center (UMMC). Also avoid cholesterol drugs such as lovastatin; medications for anxiety such as alprazolam, diazepam and lorazepam; blood-thinning medications such as warfarin and clopidogrel; and cancer drugs. The above cites examples of drugs that may interact with milk thistle and is not a comprehensive list of all medications that you should avoid.

Other Interactions

The UMMC also states that you should talk with a physician before taking milk thistle if you take or are/will be treated with antipsychotic medications such as butyrophenones and phenothiazines; phenytoin, an anti-seizure drug; and halothene, which is used during anesthesia.

Consult Your Doctor

Milk thistle shows promise in treating liver disease, but NCCAM states that more research is needed to make sure that it's beneficial. Don't replace your conventional medication with milk thistle supplements without first consulting with your treating physician. Keep in mind that milk thistle and other supplements can interact with prescription and nonprescription medications and can put you at risk for adverse effects during surgery, when you're given anesthesia. NCCAM further states that most dietary supplements have not been researched in pregnant or nursing woman and children. Liver disease is potentially fatal. Please talk to your doctor before using milk thistle for your medical condition.

References

• University of Maryland Medical Center: Milk Thistle
• National Center for Complementary & Alternative Medicine: Using Dietary Supplements Wisely
• Memorial Sloan-Kettering Cancer Center: Milk Thistle
• National Toxicology Program: Milk Thistle
• "Drug Metabolism and Disposition: The Biological Fate of Chemicals"; Milk Thistle, a Herbal Supplement, Decreases the Activity of CYP3A4; R. Venkataramanan, et al.; 2000