Berberine (Goldenseal)CAM Interactions

Potential for berberine to cause drug interactions

Berberine is used to treat gastrointestinal infections, diabetes, high blood pressure, and cholesterol. Many studies report interactions between berberine-containing products and cytochrome P450, but little is known about whether berberine alters CYP activities in humans.

Researchers at the Xiang Ya School of Medicine, in the People’s Republic of China, studied the effects of berberine on a series of drugs and P450 enzymes after repeated dosing.

First, the details.

  • Healthy men were assigned to take each treatment in random order — crossover design.
  • After 2 weeks of berberine 300 mg 3 times daily by mouth, dextromethorphan (Benylin), losartan (Cozaar), and caffeine were used to evaluate enzyme activities of CYP3A4, 2C19, 2D6, 2C9, and CYP1A2, respectively.

And, the results.

  • CYP2D6 activity decreased significantly as urinary levels of dextromethorphan/dextrorphan increased.
  • The losartan/E-3174 ratio increased significantly after berberine administration, indicating a decrease in CYP2C9 activity.
  • CYP3A4 activity was significantly inhibited as midazolam levels increased.
  • Compared to placebo, with berberine there was a significant delay in the time to maximum blood levels and elimination of midazolam from the body.
  • There were no other statistically significant differences.

The bottom line?

The authors concluded, “Repeated administration of berberine (300 mg, 3 times daily by mouth) decreased CYP2D6, 2C9, and CYP3A4 activities. Drug-drug interactions should be considered when berberine is administered.”

Careful when taking berberine at the same time as taking dextromethorphan, losartan, and midazolam.

8/29/11 20:57 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.