St. John's Wort (Hypericum perforatum)

  • Pharmacy Author:
    Omudhome Ogbru, PharmD

    Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.

  • Medical and Pharmacy Editor: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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DOSING: Dietary supplements such as St. John's wort are not regulated by the FDA, and are not subject to rigorous clinical studies that evaluate standardized drug dosages. Read product labels and discuss dosing with your doctor before taking this dietary supplement.

The most common dosage that has been used in the majority of studies is 0.3% hypericin or 5% hyperforin in a dosage of 300 to 400 mg three times daily.

DRUG INTERACTIONS: St. John's wort increases activity of several liver enzymes. Consequently, St. John's wort may decrease blood levels of drugs that are metabolized or broken-down by these enzymes. Examples of such drugs are warfarin (Coumadin), fluconazole (Diflucan), voriconazole (Vfend), itraconazole (Sporanox), fentanyl (Sublimaze), digoxin (Lanoxin), birth control pills and many other drugs.

St. John's wort should be avoided in patients taking prescription antidepressants due to the risk of serotonin syndrome. Symptoms of serotonin syndrome include agitation, hyperthermia (extreme body temperature), sweating, rapid heartbeat, and neuromuscular disturbances.

Medically Reviewed by a Doctor on 10/24/2014

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